Reports on Astronomy/Proceedings of the Thirteenth General Assembly Prague 1967 [1st ed.] 978-90-277-0139-8;978-94-010-3476-0

Table of contents :
Front Matter ....Pages i-cxvii
Commission des Ephemerides (G. M. Clemence, Vicente Planelles, W. Fricke, R. L. Duncombe, D. H. Sadler, A. Danjon et al.)....Pages 1-9
Commission de la Mecanique Celeste (Y. Hagihara)....Pages 11-61
Commission de L’Astronomie de Position (R. H. Stoy, A. A. Nemiro, W. Dieckvoss, F. P. Scott)....Pages 63-85
Commission des Instruments Astronomiques (O. A. Mel’nikov)....Pages 87-123
Commission de L’Activite Solaire (Z. Švestka)....Pages 125-195
Commission de la Radiation et de la Structure de L’Atmosphere Solaire (Luboš Perek)....Pages 197-227
Commission des Donnees Spectroscopiques Fondamentales (Charlotte Moore-Sitterly)....Pages 229-266
Addenda (Luboš Perek)....Pages 266-266
Commission Pour L’Etude Physique Des Cometes (F. L. Whipple)....Pages 267-288
Commission Pour L’Etude Physique des Planetes et des Satellites (Luboš Perek)....Pages 289-339
Commission de la Lune (D. H. Menzel, B. Bell)....Pages 341-374
Commission de la Rotation de la Terre (B. Guinot)....Pages 375-393
Commission des Positions et des Mouvements des Petites Planetes, des Cometes et des Satellites (Luboš Perek)....Pages 395-409
Commission de la Luminescence du Ciel (Franklin E. Roach)....Pages 411-427
Commission des Météores et Météorites (Peter M. Millman)....Pages 429-454
Commission de la Carte du Ciel (P. Sémirot)....Pages 455-461
Commission des Parallaxes Stellaires et des Mouvements Propres (A. N. Deutsch)....Pages 463-469
Commission de Photometrie Stellaire (V. B. Nikonov)....Pages 471-498
Commission des Etoiles Doubles (K. Aa. Strand)....Pages 499-507
Commission des Etoiles Variables (Luboš Perek)....Pages 509-565
Commission des Galaxies (R. L. Minkowski)....Pages 567-605
Commission des Spectres Stellaires (Jorge Sahade)....Pages 607-643
Commission des Vitesses Radiales (David S. Evans)....Pages 645-658
Commission de L’Heure (B. Guinot)....Pages 659-673
Commission de la Structure et de la Dynamique du Systeme Galactique (B. J. Bok, T. Elvius)....Pages 675-727
Commission de la Matiere Interstellaire et des Nebuleuses Planetaires (S. B. Pikelner)....Pages 729-762
Commission de la Constitution des Etoiles (P. Ledoux)....Pages 763-800
Commission de la Theorie des Atmospheres Stellaires (K. H. Böhm)....Pages 801-827
Commission des Amas Stellaires et des Associations (M. F. Walker)....Pages 829-855
Commission de la Radioastronomie (M. Ryle)....Pages 857-908
Addendum (Luboš Perek)....Pages 908-908
Commission de L’Histoire de L’Astronomie (E. Rybka)....Pages 909-921
Commission des Etoiles Doubles Photometriques (John E. Merrill)....Pages 923-963
Commission de la Magneto-Hydrodynamique et de la Physique des Gaz Ionises (T. G. Cowling)....Pages 965-978
Commission des Observations Astronomiques Au-Dehors de L’Atmosphere Terrestre (L. Goldberg)....Pages 979-1016
Commission des Classifications Spectrales et Indices de Couleur a Plusieurs Bandes (W. P. Bidelman)....Pages 1017-1047
Front Matter ....Pages 1049-1049
Inaugural Ceremony (Luboš Perek)....Pages 1051-1059
General Assembly (W. H. McCrea)....Pages 1061-1081
Front Matter ....Pages 1083-1083
Sommaire des Décisions Contenues dans le Rapport de L’Assemblée Générale (Luboš Perek)....Pages 1084-1091
Front Matter ....Pages 1093-1093
Commission des Ephemerides (G. A. Čebotarev, R. L. Duncombe, J. Kovalevsky, G. A. Wilkins)....Pages 1095-1101
Commission des Analyses de Travaux et de Bibliographie (Luboš Perek)....Pages 1102-1104
Commission des Telegrammes Astronomiques (Luboš Perek)....Pages 1105-1105
Commission de la Mecanique Celeste (Luboš Perek)....Pages 1106-1107
Commission de L’Astronomie de Position (Luboš Perek)....Pages 1108-1112
Commission des Instruments Astronomiques (Luboš Perek)....Pages 1113-1117
Commission de L’Activite Solaire (Luboš Perek)....Pages 1118-1130
Commission de la Radiation et de la Structure de L’Atmosphere Solaire (Luboš Perek)....Pages 1131-1134
Commission des Donnees Spectroscopiques Fondamentales (Luboš Perek)....Pages 1135-1139
Commission Pour L’Etude Physique des Cometes (Luboš Perek)....Pages 1140-1141
Commission Pour L’Etude Physique des Planetes et des Satellites (Luboš Perek)....Pages 1142-1150
Commission de la Lune (Luboš Perek)....Pages 1151-1155
Commission de la Rotation de la Terre (Luboš Perek)....Pages 1156-1160
Commission des Positions et des Mouvements des Petites Planetes, des Cometes et des Satellites (Luboš Perek)....Pages 1161-1168
Addendum (Luboš Perek)....Pages 1168-1180
Commission de la Luminescence du Ciel (Luboš Perek)....Pages 1181-1181
Commission des Meteores et Meteorites (Luboš Perek)....Pages 1182-1184
Commission de la Carte du Ciel (Luboš Perek)....Pages 1185-1186
Commission des Parallaxes Stellaires et des Mouvements Propres (Luboš Perek)....Pages 1187-1189
Commission de Photometrie Stellaire (Luboš Perek)....Pages 1190-1192
Commission des Etoiles Doubles (Luboš Perek)....Pages 1193-1195
Commission des Etoiles Variables (Luboš Perek)....Pages 1196-1201
Commission des Galaxies (Luboš Perek)....Pages 1202-1213
Commission des Spectres Stellaires (Luboš Perek)....Pages 1214-1215
Commission des Vitesses Radiales (Luboš Perek)....Pages 1216-1218
Rapport de la Session Mixte 30 et 42 (Luboš Perek)....Pages 1219-1220
Commission de L’Heure (B. Guinot)....Pages 1221-1225
Sessions Mixtes 31 et 4 (Luboš Perek)....Pages 1226-1230
Commission de la Structure et de la Dynamique du Systeme Galactique (Luboš Perek)....Pages 1231-1234
Groupe du Travail sur Regions Choisies, 23 et 24 Session Mixte (Luboš Perek)....Pages 1235-1236
Commission de la Matiere Interstellaire et des Nebuleuses Planetaires (Luboš Perek)....Pages 1237-1241
Commission de la Constitution Interne des Etoiles (Luboš Perek)....Pages 1242-1243
Commission de la Theorie des Atmospheres Stellaires (Luboš Perek)....Pages 1244-1245
Session Mixte 12 et 36 (Luboš Perek)....Pages 1246-1246
Commission des Amas Stellaires et des Associations (Luboš Perek)....Pages 1247-1248
Commission Pour L’Echange des Astronomes (Luboš Perek)....Pages 1249-1250
Commission de la Radioastronomie (Luboš Perek)....Pages 1251-1254
Commission D’Histoire de L’Astronomie (Luboš Perek)....Pages 1255-1258
Commission des Etoiles Doubles Photometriques (Luboš Perek)....Pages 1259-1260
Commission de Plasmas et Magneto-Hydrodynamique en Astrophysique (Luboš Perek)....Pages 1261-1262
Commission des Observations Astronomiques Au-Dehors de L’Atmosphere Terrestre (Luboš Perek)....Pages 1263-1267
Commission des Classifications Spectrales et Indices de Couleur a Plusieurs Bandes (Luboš Perek)....Pages 1268-1270
Commission Pour L’Enseignement de L’Astronomie (Luboš Perek)....Pages 1271-1277
Front Matter ....Pages 1279-1279
I. Short History of the International Astronomical Union (Luboš Perek)....Pages 1281-1286
Style Book (Luboš Perek)....Pages 1286-1286
Part 3 of Astronomer’s Handbook (Luboš Perek)....Pages 1287-1357

Citation preview

TRANSACTIONS OF THE

INTERNATIONAL ASTRONOMICAL UNION VOLUME XIII A- REPORTS

INTERNATIONAL COUNCIL OF SCIENTIFIC UNIONS

INTERNATIONAL ASTRONOMICAL UNION UNION ASTRONOMIQUE INTERNATIONALE

TRANSACTIONS OF THE

INTERNATIONAL ASTRONOMICAL UNION VOLUME XIIIA- REPORTS

REPORTS ON

ASTRONOMY Edited by

Lubos PEREK General Secretary of the Union

PUBLISHED FOR THE INTERNATIONAL COUNCIL OF SCIENTIFIC UNIONS WITH THE FINANCIAL ASSISTANCE OF UNESCO

SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. 1967

©Springer Science+Business Media Dordrecht, 1967 Originally published by D. Reidel Publishing Company in 1967 Softcover reprint of the hardcover 1st edition 1967

Unesco subvention- 1967- AVS/414/25

ISBN 978-94-010-3478-4 ISBN 978-94-010-3476-0 (eBook) DOI 10.1007/978-94-010-3476-0

PREFACE The present volume, XIII A, contains the corrected Reports of IAU Commissions, as presented to the XIII General Assembly of the Union, held in Prague, Czechoslovakia, from 22 to 31 August 1967. The volume, entitled "Reports on Astronomy", is an authoritative, detailed, and unique survey of the accomplishments in all branches of astronomy from 1964 to 1967. For technical reasons, the volume also contains the Report of the Executive Committee 1964-1967, which originally was to appear in Volume B. The page proofs of the present volume, assembled into the Agenda and Draft Reports, had been distributed to the Members of the Union before the General Assembly. Only errors and misprints in the Draft Reports have been corrected in the present volume: additions had to be deferred to volume XIII B in order to speed up publication. Volume XIII B, subtitled "Proceedings of the Thirteenth General Assembly", will contain: the report of the Inaugural Ceremony and of the sessions of the General Assembly; the resolutions adopted by the General Assembly and by Commissions; the proceedings of Commission meetings, and those parts of the Astronomer's Handbook which underwent changes (i.e. representation of the IAU in international scientific bodies; composition of the Executive Committee; Symposia, Colloquia, and Publications of the Union; list of Commissions and of their membership; list of Members of the Union). A separate volume, not numbered in the series of IAU Transactions, and entitled "Highlights of Astronomy as presented at the Thirteenth General Assembly of the Union 1967'' will contain the Invited Discourses, the proceedings of the Joint Discussions, and those of one or two other meetings. The proceedings of Symposia No. 33-Physics and Dynamics of Meteors, No. 34-Planetary Nebulae, and No. 35-Development of Solar Active Regions, held immediately after the General Assembly, will be published in the Symposium series of the Union. The present volume is a collective work of forty Presidents of Commissions. The personal style was preserved in preference to an entirely homogenous presentation. The reports were edited by the former General Secretary, Professor Jean-Claude Peeker, during his term of office. The extremely difficult task of subediting the volume was entrusted to the experience, patience, and competence of Miss Genevieve Drouin. All those who assisted in preparing this

volume, as well as the printer, Willmer Brothers Limited, and the publisher, D. Reidel Publishing Company, deserve the gratitude and appreciation of the Union and of the readers as well. L.

Praha 4 October 1967

PEREK

General Secretary

v

CONTENTS Report of the Executive Committee 1964-1967 Activite de l'UAI Activity of the IAU Appendice I. Rapport Financier Appendix I. Report on IAU Finances Appendice II. La Politique des Publications Appendix II. Publication Policy Appendix III Reports of the Committees of the Executive Committee Commission 5 (Analyse de Travaux et Bibliographie) Commission 6 (Telegrammes Astronomiques) Commission 38 (Echange des Astronomes) Commission 46 (Enseignement de I' Astronomie) Interunion Commission on Solar and Terrestrial Relationship Report of the Working Group on Photographic Materials

ix xvii XXV

xli lv lxiii lxxi lxxv lxxv lxxxi lxxxv lxxxix xcix cv

Reports of Commissions No. Commission Page 4· Ephemerides (Ephemerides) 7· Mecanique Celeste (Celestial Mechanics) 8. Astronomie de Position (Positional Astronomy) -Reports of the Working Groups: Photograph Catalogues of Stars to the Ninth Magnitude International Reference Star Programs 9· Instruments Astronomiques (Astronomical Instruments) -Report of the Working Group on Image Tubes for Astronomy -Rapport du Groupe de Travail sur Ia Qualite des Images et le Choix des Sites xo. Activite Solaire (Solar Activity) 12. Radiation et Structure de I'Atmosphere Solaire (Radiation and Structure of the Solar Atmosphere) -Report of the Working Group on Solar Eclipses -Report of the Working Group on Central Line Intensities 14. Donnees Spectroscopiques Fondamentales (Fundamental Spectroscopic Data) -Report of the Committee on Standards of Wavelength -Report of the Committee on Transition Probabilities -Report of the Sub-Committee on Broadening Parameters of Spectral Lines -Report of the Sub-Committee on Cross Sections -Report of the Committee on Molecular Spectra 15. Etude Physique des Cometes (Physical Study of Comets) 16. Etude Physique des Planetes et des Satellites (Physical Study of Planets and Satellites) vii

No. 1 II

63 71 72

87 no 122 125

197 227

227 229

230 233 236 238 246 267 289

viii

CONTENTS

Commission Page No. 17. La Lune (The Moon) 19. Rotation de Ia Terre (Rotation of the Earth) 20. Positions et Mouvements des Petites Planetes, des Cometes et des Satellites (Positions and Motions of Minor Planets, Comets and Satellites) -Report of the Working Committee on Orbits and Ephemerides of Comets 21. Luminescence du Ciel (Light of the Night-Sky) 22. Meteores et Meteorites (Meteors and Meteorites) -Report of the Committee on Meteorites

No.

23. Carte du Ciel 24. Parallaxes Stellaires et Mouvements Propres (Stellar Parallaxes and Proper Motions) 25. Photometrie Stellaire (Stellar Photometry) 26. Etoiles Doubles (Double Stars) 27. Etoiles Variables (Variable Stars) -Report of the Committee on the Spectra of Variable Stars -Report of the Committee on Variable Stars in Clusters

455

28

29.

30. 31. 33· 34· 35· 36. 37· 40. 41. 42. 43· 44· 45·

Galaxies -Report of the Working Group on Galaxy Photometry -Report of the Committee for Research on Supernovae -Report of the Committee on the Magellanic Clouds Spectres Stellaires (Stellar Spectra) -Report of the Committee on Spectrophotometry -Report of the Committee on Line Intensity Standards Vitesses Radiales (Radial Velocities) Heure (Time) Structure et Dynamique du Systeme Galactique (Structure and Dynamics of the Galactic System) -Report of the Committee of "Selected Areas" Matiere Interstellaire et Nebuleuses Planetaires (Interstellar Matter and Planetary Nebulae) Constitution des Etoiles (Stellar Constitution) Theorie des Atmospheres Stellaires (Theory of Stellar Atmospheres) Amas Stellaires et Associations (Star Clusters and Associations) Radioastronomie (Radioastronomy) Histoire de l'Astronomie (History of Astronomy) Etoiles Doubles Photometriques (Photometric Double Stars) Magneto-Hydrodynamique et Physique des Gaz Ionises (Magneto-Hydrodynamics and Physics of the Ionized Gases) Observations Astronomiques au-dehors de l' Atmosphere Terrestre (Astronomical Observations from outside the Terrestrial Atmosphere) Classifications Spectrales et Indices de Couleur a Plusieurs Bandes (Spectral Classifications and Multi-Band Colour Indices)

341 375 395 402 4II 429 443

463 471 499 509 542 555 567 592 594 595 607 637 639 645 659 675 719 729 763 8o1 829 857 909 923 965 979 1017

RAPPORT DU COMITE EXECUTIF 1964-1967* ACTIVITE DE L'UNION ASTRONOMIQUE INTERNATIONALE

(See English version on page xvii) Introduction

Ce rapport couvre la periode qui s'etend du I janvier I964 au 3I decembre I966. Par souci de continuite, il a ete compose selon des principes identiques a ceux qui ont guide la redaction des rapports precedents et notamment celui relatif a Ia periode I96I-63, publie dans le Volume XII B des Transactions, et approuve formellement par Ia douzieme Assemblee Generale. La periode couverte comprend le debut de l'annee I964 (jusqu'au 25 aout I964) pendant laquelle le Comite Executif actuel n'etait pas encore en fonction. Symetriquement, elle exclut le debut de l'annee I967, qui pourtant depend du Comite Executif actuel: un rapport complementaire provisoire, portant sur cette periode {I janvier-2I aout I967) sera oralement presente devant Ia treizieme Assemblee Generale, et, en cas d'approbation, publie dans Ie Volume XIII B des Transactions. Pendant Ia periode couverte par le present rapport, un certain nombre de decisions ont ete prises par le Comite Executif. Les unes, Iiees a Ia douzieme Assemblee Generale, ou prises lors de cette Assemblee, ont ete incluses dans le Volume XII B des Transactions, et ne seront pas a nouveau mentionnees ci-apres. Les autres ont ete publiees dans Ie Bulletin d'lnformation de l'UAI et sont a nouveau mentionnees ci-apres dans les paragraphes appropries. Le Bulletin d'lnformation de l'UAI a publie un grand nombre d'informations en provenance des Commissions de l'UAI, des Commissions Inter-Unions, des Services Astronomiques, etc. Ces informations sont essentiellement contenues dans Ies Draft Reports des Commissions appropriees de l'UAI, dans Ia mesure ou elles restent valides actuellement. Les problemes les plus graves rencontres par !'Union concernent les Publications et Ies Finances: a chacune de ces deux questions est consacre un appendice au present rapport. Un troisieme appendice est consacre a quelques donnees relatives aux Organisations Adherentes et aux Membres de l'Union. De plus, un certain nombre de Commissions Administratives (5, 6, 38, 46) sont considerees comme des comites du Comite Executif: leurs rapports completent Ie present rapport, auquel s'ajoutent egalement le rapport final du President de l'IUCSTR (Inter-Union Commission on Solar and Terrestrial Relationships), l'UAI ayant joue Ie role d'union-mere de cet organisme inter-union, et Ie rapport du President du Groupe de Travail sur les Emulsions Photographiques. Structure et Administration de l' UAI

L'Union Astronomique Internationale fonctionne depuis Ia douzieme Assemblee Generale dans le cadre des Statuts nouveaux adoptes lors de cette Assemblee. Administration

Le fait dominant qui a commande depuis lors la politique du Comite Executif est !'augmentation rapide des activites de !'Union: augmentation du nombre de ses Membres, de ses Commissions, des Pays Adherents, complexite croissante des relations avec les autres organisations. *Note. Le texte du Rapport et de ses deux premiers Appendices sont publies ci-apres en deux langues. Seulle texte franyais fera autorite, en cas de besoin, le texte anglais n'etant qu'une traduction du texte franyais. lX

X

RAPPORT DU COMITE EXECUTIF

Depuis l'ete I964, afin de faire face a cette situation difficile, une steno-dactylographe a ete adjointe au Secretaire Adjoint. De plus le Secretaire General et le Secretaire General Adjoint ont beneficie des services de plusieurs personnes, a Meudon et a Prague, non salariees par l'UAI, grace a la comprehension des autorites nationales fran9aises et tchecoslovaques, ce qui prouve que, meme augmente d'une personne, le personnel administratif de l'UAI est, en nombre, tres insuffisant.

II est apparu au Comite Executif qu'il etait, pour des raisons financieres claires, impossible de faire mieux, dans l'avenir immediat. C'est pourquoi des solutions ont ete recherchees en vue de simplifier !'administration, parfois tres lourde, de certains problemes: c'est en partie pour cette raison que Ia Liste de Distribution des publications de l'UAI a ete considerablement reduite, et que !'edition des Symposiums de l'UAI posterieurs au no. 3I sera confiee, si possible, a une firme privee (voir ci-apres page lx). Reunions du Comite Executif

Le Comite Executif sortant a tenu sa vingt-cinquieme reunion a Hambourg, pendant la douzieme Assemblee Generale (24 aout-3 septembre I964), sous la presidence du Professeur V. A. Ambarcumjan. Tous les membres et conseillers etaient presents. Le Comite Executif actuel a tenu sa vingt-sixieme reunion a Hambourg, le 3 septembre I964, sous la presidence du Professeur P. Swings, President. Tous les membres et conseillers etaient presents. Le Comite Executif a tenu, sous la presidence du Professeur P. Swings, les deux reunions suivantes: La vingt-septieme session a eu lieu a l'Observatoire de Nice, France, du I5 au I9 septembre I965; tous les membres et conseillers etaient presents sauf les Professeurs G. Haro et V. A. Ambarcumjan. La vingt-huitieme session a eu lieu a Prague, Tchecoslovaquie, du I6 an 20 septembre I966; tous les membres et conseillers etaient presents, sauf les Professeurs Y. Hagihara et V. A. Ambarcumjan, dont l'etat de sante avait empeche Ia participation. Entre les reunions, les affaires de !'Union ont ete conduites par correspondance. Vingt-quatre lettres circulaires ont ete envoyees par le Secretaire General et le Secretaire General Adjoint aux membres du Comite Executif. Membres de l' U AI et Organisations Adherentes La Nouvelle-Zelande a adhere a l'UAI en 1964. Aucune autre modification depuis la onzieme Assemblee Generale n' est intervenue, malgre des contacts preliminaires pris avec des representants qualifies des pays suivants: Algerie, Cuba, lndonesie, Iran, Niger, Pakistan. La Colombie a demande son adhesion qui sera proposee a la treizieme Assemblee Generale.

L' Appendice III (page lxxi) rappelle la liste des Pays Adherents et des Organisations Adherentes correspondantes.

II est a noter que la creation de 'Pays Adherents Associes' (dont la cotisation aurait ete nulle, et qui n'auraient pas eu droit de vote sur les questions ayant des implications financieres) a ete longuement envisagee. Le Comite Executif a cree en son sein en I965 un groupe de travail charge d'etudier cette question. Mais apres discussion, le Comite Executif, en I966, a decide de ne demander a I' Assemblee Generale aucune modification des Statuts a cet effet. Au I janvier I964, le nombre des Membres de l'UAI etait de 1276. Depuis cette date, la douzieme Assemblee Generale a elu 352 Membres nouveaux, cependant que nous etions informes du deces de 56 Membres; au 31 decembre I964, le nombre de Membres de !'Union est done de I 572. Une liste des Membres du deces desquels nous avons ete informes depuis le I janvier I964 figure dans l'Appendice III. Cette liste comprend malheureusement tant d'astronomes distingues qu'il est seulement possible de rendre ici hommage a ceux qui ont contribue a !'administration de !'Union.

RAPPORT D'ACTIVITE

xi

BERTIL LINDBLAD, President de l'Union Astronomique lntemationale de 1948 a 1952, a ete Directeur de l'Observatoire de Stockholm, a Saltsjobaden, depuis 1927. Ses travaux dans le domaine de la structure galactique (au sens le plus large) lui ont valu, entre autres distinctions, la medaille d'or de la Royal Astronomical Society, et la Bruce Gold Medal de la Societe Astronomique du Pacifique. II a ete President de l'Academie Royale Suedoise des Sciences. II laissera le souvenir d'un ami bienveillant et humain, autant que celui d'un astronome distingue (1895-1965). RoBERT METHVEN PETRIE, Vice-President de !'Union Astronomique Intemationale de 1958 a 1964, etait Directeur du Dominion Astrophysical Observatory, a Victoria, Canada. Ses travaux de spectroscopic stellaire, appliquee notamment aux problemes des parallaxes spectroscopiques, lui ont valu de nombreuses distinctions. II etait honore du titre de 'Dominion Astronomer', et etait President de la Royal Astronomical Society of Canada. Ses collegues garderont de lui le souvenir d'un savant eminent, mais aussi d'un ami plein d'humour et de sagesse (1906-1966). ANDRE DANJON, President de !'Union Astronomique Intemationale de 1958 a 1931, etait, avant sa retraite, Directeur de l'Observatoire de Paris et Professeur ala Sorbonne depuis 1945. Ses travaux d'optique et de photometric, puis ses recherches d'astronomie fondamentale, et particulierement la conception et !'utilisation de !'astrolabe impersonnel a prisme qui porte son nom, lui ont valu de tres nombreuses distinctions, notamment la medaille d'or de la Royal Astronomical Society et la medaille d'or du C.N.R.S. II etait Membre de l'Academie des Sciences de Paris, associe etranger de plusieurs institutions academiques, et, en France, il a preside de nombreux comites. Ses collegues et ses eleves n'oublieront jamais ce qu'ils doivent a SOn energie, et en garderont un tres emu SOUVenir (189o-1967). Commissions de l'UAI

Ce volume des Agenda and Draft Reports contient des rapports excellents et detailles, prepares par les Presidents de chacune des 38 Commissions de l'Union, assistes par leur Vice-President, leur Comite d'Organisation, les responsables des divers groupes de travail ou comites ayant ete crees au sein de ces Commissions par les Commissions ellesmemes. Depuis la douzieme Assemblee Generale deux nouvelles commissions ont ete creees: la Commission 45 (Classifications Spectrales et Indices de Couleur a Plusieurs Bandes) et la Commission 46 (Enseignement de l' Astronomic); cette derniere fonctionne comme co mite du Comite Executif. En raison du deces du Professeur R. M. Petrie, le Professeur D. S. Evans a ete nomme President par interim de la Commission 30 (Les Vitesses Radiales), cependant que le Professeur F. L. Whipple etait nomme President par interim de la Commission 6 (Telegrammes Astronomiques) en raison du deces du Dr A. G. Hogg. Entre les Assemblees Generales, les Commissions ont coopte parmi les Membres de l'UAI un certain nombre de membres. De plus, des Presidents ont souhaite s'adjoindre les services d'astronomes non-membres de l'UAI. En vue de simplifier la procedure, il a ete demande aux Presidents de les considerer pour taus les problemes pratiques comme des Membres de l'UAI. Des propositions relatives aux nouvelles compositions des Commissions, comprenant ces membres cooptes et les nouveaux Membres elus par 1'Assemblee Generale seront faites par les Presidents, les listes publiees dans le Volume XII C des Transactions servant de point de depart a ces propositions. Entre les Assemblees Generales, les Commissions ont pris !'initiative d'un certain nombre de Colloques et de proiets finances par l'UAI.

xii

RAPPORT DU COMITE EXECUTIF

Colloques des Commissions de l' U AI

(tenus entre le

I

janvier 1964 et le 31 decembre 1966).

IAU Colloquium on The Position of Variable Stars in the Hertzsprung-Russell Diagram, Bamberg, ro-15 August 1965 (Commissions 27 and 42). IAU Colloquium on Interstellar Grains, Troy, New York, 24-26 August 1965 (Commission 34) IAU Colloquium on The Blanketing Effect, Heidelberg, 17-19 March 1966 (Commission 36) IAU Colloquium on Late-Type Stars, Trieste, 13-16 June 1966 (Commissions 14, 29, 35, 36). IAU Colloquium on Atomic Collisions, Boulder, II-r6 July 1966 (Commission q). IAU Colloquium on the Evolution of Double Stars, Uccle, 29 August-2 September 1966 (Commission 26). Entreprises specifiques des Commissions, approuvees par la douzieme Assemblie Generale

La liste de ces entreprises, et des depenses correspondantes, se trouvent page xxx, dans l'Annexe au present rapport traitant des Finances de l'Union. Pour la plupart, ces entreprises constituent le prolongement d'entreprises precedentes, et n'appellent aucun commentaire. Nous noterons cependant que les credits attribues aux Cartes d'Etoiles Variables de !'Hemisphere Sud, et ceux attribues au Catalogue sur Cartes des Amas et Associations n'ont pas ete utilises. Cette derniere entreprise a du etre retardee, et le Comite Executif a donne son accord pour la realisation, a partir de 1967, de ce projet par les editions de 1' Academie des Sciences de Budapest. La somme attribuee au Dr Bateson pour les Cartes d'Etoiles Variables de !'Hemisphere Sud devra etre versee en 1967. Entreprises specifiques des Commissions, approuvees, entre les douzieme et treizieme Assemblies Generales, par le Comite Executif 11 s'agit: (a) de la reedition de !'Atlas of Representative Cometary Spectra, par l'Institut d'Astrophysique de Liege, demandee par de nombreux chercheurs; (b) de !'edition, par le Dr Sahade, de !'Information Bulletin for the Southern Hemisphere, publication tres lue dans !'Hemisphere Sud, et particulierement bien preparee et presentee; (c) de la reedition, sous forme de feuilles mobiles, du livre ancien, et maintenant depasse, de Rigaux, Les Observatoires Astronomiques et les Astronomes, par l'Observatoire Royal de Belgique a Uccle. Cette nouvelle forme de publication permettra l'actualisation permanente de I' ouvrage. Symposiums Symposiums de l' UAI Pendant la periode couverte par le present rapport, les Symposiums suivants ont ete organises par l'UAI:

no. 23 24 25 26 27

Sujet Astronomical Observations from Space Vehicles Spectral Classification of Multi-Colour Photometry The Theory of Orbits in the Solar System and in Stellar Systems Abundance Determination in Stellar Spectra The Construction of Large Telescopes

Lieu

Date

Saltsjobaden

Aout 1964

Thessaloniki

Aout r 964

Utrecht Tucson, Pasadena

Aout 1964 Avril 1965

RAPPORT D'ACTIVITE

28 29 30 31

Cosmical Gas Dynamics. V. Aerodynamical Phenomena in Stellar Atmospheres Instability Phenomena in Galaxies Determination of Radial Velocities and their Applications Radio Astronomy and the Galactic System

xiii

Nice

Septembre 1965

Burakan Toronto

Mai 1966 Juin 1966

Noordwijk

Septembre 1966

Les Symposiums nos. 23, 24, 25 and 26 ont ete organises peu de temps avant la douzieme Assemblee Generale de l'UAI. Le Symposium no. 28 a ete organise en cooperation avec l'U nion Internationale de Mecanique Theorique et Appliquee (IUTAM), le Symposium no. 31 avec !'Union Radio Scientifique Internationale (URSI). Le Symposium no. 32, organise conjointement avec !'Union Internationale de Geodesie et de Geophysique (IUGG), aura lieu a Stresa, Italie, du 21 au 25 mars 1967 et portera sur 'Continental Drift, Secular Motion of the Pole and Rotation of the Earth'. Les Symposiums nos. 33, 34, 35, portant respectivement sur 'Physics and Dynamics of Meteors', 'Planetary Nebulae', 'The Structure and Development of Solar Active Regions', auront lieu dans la semaine qui suivra la treizieme Assemblee Generale de l'UAI a Prague, et se tiendront respectivement a Tatranska Lomnica, Tchecoslovaquie (nos. 33 et 34) et a Budapest, Hongrie (no. 35). Symposiums auxquels l' UAI a participe The History of Astronomy (IUPHS-UAI)

Hambourg

Aout 1964

The Trajectories of Artificial Celestial Bodies as Determined from Observations (IUTAM-COSPAR-UAI)

Paris

Avril 1965

Planetary Atmospheres and Surfaces as Deduced from Radio Observations (URSI-U AI)

Dorado Beach

Mai 1965

COSPAR Sixth International Space Science Symposium (sessions on Galactic and Extragalactic Phenomena and Space Research) (COSPAR-UAI)

Buenos Ayres

Mai 1966

Solar Terrestrial Physics (URSI, IUGG-IAGA, UAI)

Belgrade

Aout 1966

L'UAI etait de plus representee a de nombreux symposiums, et aux assemblees de nombreux organismes de l'ICSU; ces representations ont ete annoncees dans les Bulletins d'Information successifs de l'UAI. Relations avec les autres Organisations Representation de l' UAI 1. Conseil International des Unions Scientifiques. Le Secretaire General (D. H. Sadler) a represente !'Union ala seconde reunion du Comite Executif de l'ICSU a Londres (juin 1964). Le Secretaire General a represente !'Union a la 3eme reunion du Comite Executif de l'ICSU a Munich (avril 1965). Le President (P. Swings) et le Secretaire General (J.-C. Peeker) ont represente l'Union a la onzieme Assemblee Generale de l'ICSU a Bombay (janvier 1966). Le Secretaire General a represente !'Union aux 4eme et 5eme reunions du Comite Executif de l'ICSU a Bombay (janvier 1966). Le Secretaire General Adjoint (L. Perek) a egalement assiste ala onzieme Assemblee Generale de l'ICSU. Le Secretaire General a represente l'Union a la 6eme reunion du Comite Executif de l'ICSU a Monaco (septembre 1966).

Le Secretaire General est actuellement le representant designe de l'Union au Comite Executif de l'ICSU.

xiv

RAPPORT DU COMITE EXECUTIF

2. Organismes de l'ICSU. L'Union participe aux travaux d'un certain nombre de comites speciaux et scientifiques, de comites et de commissions interunions fondes sous les auspices de l'ICSU. On trouvera dans le Volume XII C des Transactions, p. 13 et sq., des donnees sur ces organismes. La liste suivante donne seulement l'etat actuel de la representation de l'UAI au sein de ces organismes. (a) Committee on Space Research (COSPAR): L. Gratton. (b) Special Committee for the International Years of the Quiet Sun (IQSY): G. Righini (Vice-President); R. Michard (reporter for 'Solar Activity'). (c) Comite International de Geophysique (CIG): G. Righini (Vice-President); R. Michard. (d) Federation of Astronomical and Geophysical Services (FAGS): D. H. Sadler (VicePresident); B. Guinot. (e) Inter-Union Commission on Frequency Allocations for Radioastronomy and Space Science (IUCAF): J. F. Denisse; V. A. Sanamian; F. G. Smith (Chairman); A. Unsold. (f) Inter-Union Commission on Solar-Terrestrial Physics (IUCSTP): Z. Svestka. (g) Inter-Union Commission on Spectroscopy: B. Edlen; G. Herzberg; J. G. Phillips; M. J. Seaton. (h) Commission Inter-Union sur l'Enseignement des Sciences (CIES-IUCST): E. Schatzman. (i) ICSU Abstracting Board (lAB): J. Kleczek. (j) Committee for Data on Science and Technology (CODATA): Ch. Moore-Sitterly.

3· Autres organisations. L'Union est representee dans: (a) La Fondation Internationale du Pic-du-Midi, par A. Lallemand. (b) Le Comite Consultatif pour la Definition de la Seconde (CCDS), du Bureau International des Poids et Mesures, par W. Markowitz et N. Stoyko. (c) Le Comite Consultatif pour la Definition du Metre, du Bureau International des Poids et Mesures, par Ch. Moore-Sitterly. (d) Les differents services de FAGS: Bureau International de l'Heure (BIH): H. M. Smith; N. N. Pavlov. International Polar Motion Service: (Organizing Committee of IAU Commission 19). Quarterly Bulletin of Solar Activity: (Organizing Committee of IAU Commission 12). International Ursigrams and World Days Service (IUWDS): R. Michard. Solar Particles and Radiations Monitoring Organizations (SPARMO): C. de Jager. Remarque: Les Commissions Inter-Unions sur les Relations Soleil-Terre (IUCSTR) et sur l'Ionosphere (IUCI) ont acheve leurs travaux. L'Union Astronomique lnternationale y etait representee, respectivement par C. W. Allen (President), R. Giovanelli, E. Mustel, M. Waldmeier pour la premiere, et par C. W. Allen (Secretary), R.N. Bracewell, V. G. Fesenkov, K. 0. Kiepenheuer, pour la seconde. Relations directes avec l' UNESCO

L'Union a beneficie de contrats directs avec l'UNESCO, dans des buts varies; ils figurent, ci-apres, dans les bilans financiers. I1 s'est agi d'abord d'aider la reunion de deux Symposiums de l'UAI (nos. 23 et 25) sur des sujets d'un interet general suffisant pour legitimer l'aide de l'UNESCO. Ce fut ensuite une aide reguliere a la Commission 38, par le moyen d'un contrat forfaitaire, destine a couvrir une partie des depenses de Ia Commission, specialement celles entrainees par les echanges d'astronomes interessant des pays en voie de developpement.

RAPPORT D'ACTIVITE

XV

Enfin, le principe d'une 'Ecole Annuelle de Jeunes Astronomes' a ete retenu, aIa suite d'une reunion d'un groupe d'experts, travaillant sous l'egide de Ia Commission 46 de l'UAI. Un credit prevu a cet effet pour 1966 n'a pu etre utilise en raison du faible delai imparti a Ia preparation de !'ecole; un contrat de remplacement a permis !'attribution a un etudiant d'un pays en voie de developpement d'une bourse d'etudes dans un observatoire bien equipe. En 1967, la premiere ecole d'ete de l'UNESCO-UAI aura lieu a Manchester, sous la direction du Professeur Z. Kopal. Le Secretaire General en est le Dr J. Kleczek. II s'agit Ia d'une experience, qui a ete longuement debattue au sein du Comite Executif. Celui-ci aurait prefere sans doute que l'UNESCO aidat plut6t l'UAI a assumer ses charges normales, devenues trop lourdes. D'autres collegues pensent qu'une ecole d'ete n'est efficace que si elle joue le role de pre-selection, les meilleurs eleves qu'elle permet de detecter effectuant ensuite de longs sejours dans des observatoires equipes. Quoiqu'il en soit, les resultats de !'experience seront examines avec attention, en vue des actions a venir. L'UAI est desireuse de maintenir avec !'UNESCO de tels contrats: cette possibilite s'est revelee fructueuse et l'UAI tient a en exprimer a !'UNESCO sa reconnaissance. Relations avec l' ICSU et ses organismes L'ICSU est l'organisme dont depend !'Union le plus directement: il verse a l'UAI la subvention de !'UNESCO (non compris les contrats directs) et coordonne les actions interunions. Cette aide est precieuse, et necessaire a l'UAI. Malheureusement le nombre d'Unions membres de l'ICSU augmente, et la subvention de l'UNESCO a l'ICSU reste sans changement: il est done difficile que la subvention re~ue par l'UAI puisse croitre. De plus la creation de nouveaux organismes interunions, en for~ant l'UAI a rembourser les frais de ses representants, qui doivent participer a des reunions assez frequentes et souvent lointaines, impose une charge a !'Union. C'est pourquoi, tout en poussant au developpement de la cooperation interdisciplinaire, l'UAI a toujours eu pour politique de favoriser les efforts de regroupements, et d'oeuvrer pour une grande efficacite. Ainsi a-t-elle joue un role important dans la reorganisation des comites interesses a la physique des relations Solei!-Terre: suppression de l'IUCSTR, de l'IUCI, fin prochaine de CIG et de l'IQSY, creation de l'IUCSTP qui devrait avoir avant tout un role de coordination: autant de faits recents qui contribueront, sans doute, a !'amelioration de la cooperation interdisciplinaire dans un domaine essentiel. Le Comite Executif de l'UAI a aussi souhaite renforcer le role des Unions, et par consequent a toujours manifeste son opposition au developpement de comites nationaux independants consacres a des questions interdisciplinaires, les structures nationales devant conserver le caractere interdisciplinaire des structures internationales. L'UAI a participe, avec de nombreuses Unions (IUTAM, UGGI, URSI) et Comites (COSPAR, IQSY) a !'organisation de symposiums (voir ci-dessus p. xiii). CONCLUSIONS GENERALES

La periode de trois ans qui vient de s'ecouler a ete reellement difficile. Certes, les Membres de !'Union, et parmi eux, principalement les Presidents des Commissions, les Vice-Presidents, les membres des Comites d'Organisation des Commissions, les responsables des symposiums et colloques, les responsables de divers services, les representants de l'UAI au sein de divers organismes, ont accompli un travail admirable.

XVI

RAPPORT DU COMITE EXECUTIF

Symetriquement, le Bureau Administratif de l'UAI, avec le souci permanent de ne pas exceder Ies possibilites financieres de l'UAI, a fait de son mieux pour les y aider, et pour contribuer a l'essor de l'astronomie mondiale. On a notamment tente, dans ce but, d'ameliorer et de simplifier certaines methodes administratives, cependant qu'un grand effort etait fait pour maintenir les publications de l'UAI a un niveau eleve. Pourtant tout ne va pas pour le mieux dans le meilleur des mondes: Ia nouvelle politique des publications de l'UAI, qui trouve son origine dans le desir legitime de diffuser mieux des publications d'une qualite amelioree, est couteuse. De plus, sa mise en application, qui implique des relations etroites entre le Secretaire General, en France, l'imprimeur et l'editeur, au Royaume-Uni, rencontre des difficultes pratiques, accrues encore par des difficultes internes (d'ailleurs momentanees) a la firme chargee de !'impression, et par le changement, en 1966, du Secretaire Adjoint de l'UAI. Les publications sont en verite d'une qualite satisfaisante, mais la production est trop lente, et des difficultes de distribution se presentent. Ces difficultes genent bien evidemment les relations entre le Bureau Administratif et les Membres de l'UAI. De plus la vente reste insuffisante. Ces relations, a vrai dire, sont fondees sur une tradition ambigue. L'UAI est une des rares Unions a etre constituee de membres individuels. Ceux-ci ne payent aucune cotisation, aucun droit; mais, de plus en plus nombreux, ils rec;oivent gratuitement des publications de plus en plus epaisses, ils utilisent les services d'organismes finances par l'Union, ils beneficient des contrats scientifiques que l'Union favorise largement. De plus la contribution des pays est modeste, eu egard aux budgets sans cesse croissants de l'Astronomie dans ces pays, surtout a l'ere du developpement rapide de Ia Radioastronomie et de la Recherche Spatiale. La contribution annuelle des pays dont la cotisation est la plus elevee est egale a cinq fois le montant du voyage aller et retour entre !'Amerique du Nord et l'Europe; ou au cout de !'impression et de la distribution de deux Bulletins d'Information; ou encore ala contribution de l'UAI a !'organisation d'un seul symposium! I1 n'y a que deux solutions possibles. Ou bien une certaine justice financiere est retablie, et la tradition genereuse de l'Union temperee: les Membres devraient payer une cotisation; ses publications seraient toutes vendues et non plus partiellement distribuees gratuitement (cette mesure est deja en cours d'application); les observatoires accepteraient de prendre le relais de l'Union dans le financement des entreprises specifiques des Commissions. Ou bien, une certaine liberalite est maintenue, notamment en ce qui concerne !'adhesion des Membres et les entreprises specifiques: mais les organisations adherentes devraient accepter une augmentation de leur cotisation (voir ci-dessous page xxv). Le Comite Executif est aujourd'hui convaincu qu'une attitude differente est impossible, et qu'un certain archa1sme trop genereux des budgets de l'UAI n'est plus aujourd'hui de mise. De plus, il est certain que le 'gigantisme' croissant de l'Union devra dans peu de temps faire place a de nouvelles structures. Preparer cette mutation sera le role du prochain Comite Executif.

REPORT OF THE EXECUTIVE COMMITTEE 1964-1967* ACTIVITY OF THE INTERNATIONAL ASTRONOMICAL UNION

(voir texte

fran~ais,

page ix)

INTRODUCTION

The present report covers the period from I January 1964 to 31 December 1966. For the sake of continuity, it has been prepared in accord with the principles governing previous reports, especially that of the period 1961-I963, formally approved by the twelfth General Assembly, and published in Volume XII B of the Transactions. The period under report includes the first half of the year 1964 (until 25 August 1964) which fell under the responsibility of the former Executive Committee. On the other hand, it does not include the first half of the year 1967, still within the responsibility of the present Executive Committee. An oral complementary report to cover this period (1 January to 21 August 1967) will be presented to the thirteenth General Assembly and, if approved, published in Volume XIII B of the Transactions. The Executive Committee has reached a number of decisions during this period. Those in connection with the twelfth General Assembly, or approved by it, were published in Volume XII B of the Transactions and will not be repeated here. Those taken at later dates have been published in the IA U Information Bulletin, and will be referred to in the appropriate paragraphs that follow. Reports on the activity of IAU Commissions, Inter-Union Commissions, Astronomical Services, etc., published in the Information Bulletin, have been incorporated into the Draft Reports of Commissions, in so far as they still apply. The most serious problems of the Union are those concerning publication and finance; they are pealt with in two separate appendices. A third appendix is devoted to factual data concerning Adhering Countries and IA U Members. Four administrative Commissions (5, 6, 38 and 46) are now treated as committees of the Executive Committee; their reports follow immediately after this Report, on page lxxv. The final reports of the President of IUCSTR (Inter-Union Commission on Solar and Terrestrial Relationships), of which the IAU was the parent Union, and of the President of the Working Group on Photographic Materials, are also added to the present Report, on page xcix. Structure and Administration of the IA U

Since the twelfth General Assembly, the International Astronomical Union has operated in accord with the provisions of the new Statutes, as adopted at that General Assembly. Administration The Executive Committee has had to cope with a great intensification in the activity of the Union: the number of its Members increased, as did that of its Commissions and Adhering Organizations; relations with other organizations became more involved. This difficult situation was met, in the summer of 1964, by adding a shorthand-typist to the existing staff. Moreover, the General Secretary and the Assistant General Secretary had the benefit of the services of several assistants, in both Meudon and Prague, generously *Note. The text of the report and of its Appendices I and II are hereafter published in two languages. The French text being the original, from which the English text has been translated, is the only one to be authoritative, in case of need. xvii B

XV111

REPORT OF THE EXECUTIVE COMMITTEE

provided by the French and Czechoslovak authorities. Evidently, though re-inforced by one additional member, the staff of the Administrative Office of the Union is still largely insufficient. The Executive Committee realizes that, the financial situation of the Union being as it is, no improvement is possible in the near future. The only remedy seems to be in a simplification of IAU administration, rather cumbersome the last years: partly for this reason, it has been decided to curtail the IAU Distribution List and to arrange for the Symposium volumes to be published by a commercial firm from Symposium no. 32 onwards (see page lxviii below). Meetings of the Executive Committee The former Executive Committee held its twenty-fifth meeting in Hamburg during the twelfth General Assembly (from 24 August to 3 September I964) under the presidency of Professor V. A. Ambarcumjan. All members and councillors were present. The present Executive Committee held its twenty-sixth meeting in Hamburg, on 3 September I964, under the presidency of Professor P. Swings. All members and councillors were present. The Executive Committee, presided over by Professor P. Swings, met as follows during the period under report: The twenty-seventh meeting was held at the Nice Observatory, France, from IS to I9 September I965; all members and councillors were present except Professor G. Haro and Professor V. A. Ambarcumjan. The twenty-eighth meeting was held in Prague, Czechoslovakia, from I6 to 20 September I966; all members and councillors were present, except Professor Y. Hagihara and Professor V. A. Ambarcumjan, who was prevented from attending by illness. Between meetings, the business of the Union was conducted by correspondence. Twenty-four circular letters were sent from the General Secretary and the Assistant General Secretary to the members of the Executive Committee. Members of the IA U and Adhering Countries New Zealand has adhered to the Union since I964. No other modification has occurred since the twelfth General Assembly, though preliminary consultations have been held with representatives of the following countries: Algeria, Cuba, Indonesia, Iran, Nigeria and Pakistan. Columbia has applied for adhesion, and its application will be submitted to the thirteenth General Assembly. The list of Adhering Countries and corresponding Adhering Organizations is given in Appendix III (page lxxi). It should be noted that much thought was given to the creation of a new category of membership, that of 'Associated Adhering Countries'. Countries adhering in this category would have paid no contribution, but would have had no right to vote on questions with financial implications. The Executive Committee formed a working group from among its members to investigate this problem; but after a lengthy discussion, the Executive Committee decided, in I966, not to ask the General Assembly to modify the Statutes to this effect. The number of IAU Members was I276 on I January I964. Since then, the twelfth General Assembly has elected a further 352 new Members. On the other hand, the General Secretary has been informed of the decease of 56 Members, so that the Union had I572 Members on 3 I December I 964. The list of the Members whose decease has been notified since 1 January I964 is given in Appendix Ill. Unfortunately this list includes so large a number of eminent scientists that it is possible only to pay hereafter separate tribute to the memory of those who have contributed greatly to the administration of the Union: BERTIL LINDBLAD, President of the International Astronomical Union (I948-I952), was Director of the Stockholm Observatory, Saltsjobaden, from 1927. His achievements in the domain of the Galactic Structure (in the broadest sense) were rewarded by the award of

ACTIVITY REPORT

xix

the Gold Medal of the Royal Astronomical Society, and the Bruce Gold Medal of the Astronomical Society of the Pacific, beside other distinctions. He was President of the Royal Swedish Academy of Sciences. He will be remembered as a good friend, full of understanding and humanity, as well as a distinguished astronomer (I895-1965). ROBERT METHVEN PETRIE, Vice-President of the International Astronomical Union (1958-x964), was Director of the Dominion Astrophysical Observatory, Victoria, Canada. His work in the domain of stellar spectrography, applied especially to the problem of spectroscopic parallaxes, was rewarded by numerous distinctions. He was honored with the title of 'Dominion Astronomer' and was President of the Royal Astronomical Society of Canada. His colleagues will remember him as an outstanding scholar, but also as a friend full of humour and wisdom (1906-x966). ANDRE DANJON, President of the International Astronomical Union from 1958 to 1961, was, before he retired, Director of the Observatoire de Paris and Professor at the Sorbonne from I945· His achievements in the domain of photometry, his research into fundamental astronomy and, in particular, his conception and application of the impersonal prismatic astrolabe, which was given his name, brought him many distinctions, including the Gold Medal of the Royal Astronomical Society and the Gold Medal of the C.N.R.S. He was member of the Academie des Sciences de Paris, associate member of numerous foreign academic institutions and president of a number of committees in France. His colleagues and pupils will never forget how much they owe to him, and they will always treasure his memory (189o-I967). Commissions of the IAU

The volume of Agenda and Draft Reports includes as usual the excellent reports prepared by the Presidents of each of the 38 Commissions of the Union, assisted by their Vice-Presidents, Organizing Committees, those responsible for the various working groups or committees formed within the Commissions, and by the Commissions themselves. At the twelfth General Assembly, two new commissions were established: Commission 45 (Spectral Classification and Multi-Band Colour Indices), and Commission 46 (Teaching of Astronomy); the latter is regarded as a committee of the Executive Committee. Professor R. M. Petrie has been succeeded by Professor D. S. Evans, nominated as Acting President of Commission 30 (Radial Velocities), and Professor F. L. Whipple has been nominated Acting President of Commission 6 (Astronomical Telegrams) to replace the late Dr A. G. Hogg. Between the General Assemblies, Commissions have co-opted a number of new members from among the Members of the Union. Moreover, some Presidents wished to obtain assistance from astronomers who are non-members of the Union; they have been asked to regard them as Members for all practical purposes. The Presidents will prepare proposals for the new composition of Commissions including co-opted members and new Members to be elected by the General Assembly. The list published in Volume XII C of the Transactions wiii serve as a starting point for these proposals. Between the General Assemblies, Commissions organized several Colloquia, and other projects financed by the IAU. Colloquia of IAU Commissions (held between I January 1964 and 31 December 1966) IAU Colloquium on The Position of Variable Stars in the Hertzsprung-Russell Diagram, Bamberg, xo-15 August 1965 (Commissions 27 and 42). IAU Colloquium on Interstellar Grains, Troy, New York, U.S.A., 24-26 August 1965 (Commission 34).

REPORT OF THE EXECUTIVE COMMITTEE

XX

IAU Colloquium on The Blanketing Effect, Heidelberg, I7-I9 March I966 (Commission 36). IAU Colloquium on Late-Type Stars, Trieste, Italy, I3-I6 June I966 (Commissions If, 29, 35. 36). IAU Colloquium on Atomic Collisions, Boulder, Colorado, U.S.A., II-I6 July I966 (Commission If). IAU Colloquium on the Evolution of Double Stars, Uccle, 29 August-2 September I966 (Commission 26). Specific Projects of Commissions, approved by the twelfth General Assembly

The list of such projects, with the corresponding expenditure, is given on page xlvi in Appendix I to the present report, dealing with the finances of the Union. These projects are, as a rule, continuations of previous projects and thus need no comment. It will be seen, however, that the grants allocated to Southern Variable Stars Charts, and to the Catalogue of Star Clusters have not been used. The latter project has been delayed, and the Executive Committee has now agreed to a proposal that it be published by the Publishing Office of the Academy of Sciences, Budapest, from I967 onwards. The grant made to Dr Bateson for the Southern Variable Stars Charts will have to be paid in I967. Specific Projects of Commissions approved, between the twelfth and thirteenth General Assemblies, by the Executive Committee

The projects are as follows: (a) A new edition of the Atlas of Representative Cometary Spectra by the Institut d' Astraphysique de Liege, to meet the needs of many scientists. (b) The publication, by Dr Sahade, of the Information Bulletin for the Southern Hemisphere. This publication, in great demand in the Southern Hemisphere, is particularly well prepared and presented. (c) A new edition, in the form of a loose-leaf catalogue, of the now outdated catalogue by Rigaux, Les Observatoires Astronomiques et les Astronomes; this is a project of the Observatoire Royal de Belgique in Uccle. The revised form of publication will allow the catalogue to be kept up to date. .Symposia IA U Symposia

During the period covered by the present report, the following symposia were organized by the Union: no. 23 2f 25 26 27 28

Subject Astronomical Observations from Space Vehicles Spectral Classification and Multi-Colour Photometry The Theory of Orbits in the Solar System and in Stellar Systems Abundance Determination in Stellar Spectra The Construction of Large Telescopes Cosmical Gas Dynamics. V. Aerodynamical Phenomena in Stellar Atmospheres

Place

Date

Liege Saltsjobaden

August I964

Thessaloniki

August 1964

Utrecht Tucson, Pasadena Nice

August I964 April I965 September 1965

ACTIVITY REPORT no. 29 30 3I

Subject Instability Phenomena in Galaxies Determinations of Radial Velocities and their Applications Radio Astronomy and the Galactic System

XXI

Place

Date

Bjurakan Toronto Noordwijk

September I966

Symposia nos. 23, 24, 25, and 26 had been held shortly before the twelfth General Assembly of the IAU. Symposium no. 28 was organized in co-operation with the International Union of Theoretical and Applied Mechanics (IUTAM), Symposium no. 3 I in co-operation with the International Union of Scientific Radio (URSI). Symposium no. 32, organized jointly with IUGG, will be held in Stresa, Italy, from 2I to 25 March I967, and is to deal with 'Continental Drift, Secular Motion of the Pole, and Rotation of the Earth'. Symposia nos. 33, 34, 35, on 'Physics and Dynamics of Meteors', 'Planetary Nebulae' and 'The Structure and Development of Solar Active Regions' respectively, will be held in Tatranska Lomnica, Czechoslovakia (nos. 33 and 34), and in Budapest, Hungary (no. 35). Symposia with IA U participation The History of Astronomy (IUPHS-IAU), Hamburg, August I964. The Trajectories of Artificial Celestial Bodies as Determined from Observations (IUTAMCOSPAR-IAU), Paris, April I965. Planetary Atmospheres and Surfaces as Deduced from Radio Observations (URSI-IAU), Dorado Beach, Puerto-Rico, U.S.A., May I965. COSPAR Sixth International Space Symposium (sessions on Galactic and Extragalactic Phenomena and Space Research) (COSPAR-IAU), Buenos-Aires, May I966. Solar-Terrestrial Physics (URSI-IUGG-IAGA-IAU), Belgrade, August I966. Moreover, the IAU was represented at numerous Symposia and at Assemblies of many ICSU Organizations; such representations were announced in the !AU Information Bulletins. Relations to Other Organizations IA U Representation I. International Council of Scientific Unions. The General Secretary (then D. H. Sadler) represented the Union at the second meeting of the ICSU Executive Committee in London (June I964). The General Secretary represented the Union at the third meeting of the ICSU Executive Committee in Munich, April 1965. The President and the General Secretary represented the Union at the eleventh General Assembly of ICSU in Bombay (January I966). The General Secretary represented the Union at the fourth and fifth meetings of the ICSU Executive Committee (Bombay, January 1966). The Assistant General Secretary also attended the eleventh General Assembly of ICSU. The General Secretary represented the Union at the sixth meeting of the ICSU Executive Committee, in Monaco, September I966. The General Secretary is the present representative of the Union on the Executive Committee of ICSU. 2. ICSU Organizations. The Union participates in the activity of a number of Special and Scientific Committees, Inter-Union Commissions and Commissions established and sponsored by ICSU. Particulars of these organizations are given on pages I3 onwards of Volume XII C of the Transactions.

REPORT OF THE EXECUTIVE COMMITTEE

xxu

The following list gives only the present state of IA U representation in these organizations: (a) Committee on Space Research (COSPAR): L. Gratton. (b) Special Committee for the International Years of the Quiet Sun (IQSY): G. Righini (Vice-President); R. Michard (reporter for 'Solar Activity'). (c) Comite International de Geophysique (CIG): G. Righini (Vice-President); R. Michard. (d) Federation of Astronomical and Geophysical Services (FAGS): D. H. Sadler (VicePresident); B. Guinot. (e) Inter-Union Commission on Frequency Allocations for Radioastronomy and Space Science (IUCAF): J.-F. Denisse; V. A. Sanamian; F. G. Smith (Chairman); A. Unsold. (f) Inter-Union Commission on Solar-Terrestrial Physics (IUCSTP): Z. Svestka. (g) Inter-Union Commission on Spectroscopy: B. Edlen; G. Herzberg; J. G. Phillips; M. J. Seaton. (h) Inter-Union Commission on Science Teaching (CIES-IUCST): E. Schatzman. (i) ICSU Abstracting Board (lAB): J. Kleczek. (j) Committee for Data on Science and Technology (CODATA): Ch. Moore-Sitterly. 3· Other Organizations. The Union is represented on the following Organizations: (a) La Fondation Internationale du Pic-du-Midi, by A. Lallemand. (b) Le Comite Consultatif pour la Definition de la Seconde (CCDS) du Bureau International des Poids et Mesures, by W. Markowitz and N. Stoyko. (c) Le Comite Consultatif pour la Definition du Metre du Bureau International des Poids et Mesures, by Ch. Moore-Sitterly. (d) Various Services of FAGS, that is on the directing boards of: Bureau International de l'Heure (BIH), by H. M. Smith, N. N. Pavlov. International Polar Motion Service, by the Organizing Committee of IAU Commission I g. Quarterly Bulletin of Solar Activity, by the Organizing Committee of IAU Commission 12.

International Ursigrams and World Days Service (IUWDS), by R. Michard. Solar Particles and Radiations Monitoring Organization (SPARMO), by C. de Jager. Note: The Inter-Union Commission on Solar and Terrestrial Relationships (IUCSTR), and that on the Ionosphere (IUCI), have terminated their activities. The IAU was represented by C. W. Allen (President), R. Giovanelli, E. Mustel and M. Waldmeier on the former, and by C. W. Allen (Secretary), R. N. Bracewell, V. G. Fesenkov, K. 0. Kiepenheuer on the latter. Direct Relations with UNESCO The Union had the benefit of various direct contracts with UNESCO, as indicated in the financial report. The first contract provided for a grant towards two IAU Symposia (nos. 23 and 25), whose subjects were sufficiently broad to justify UNESCO assistance. The second contract provided for regular financial assistance to Commission 38, partly to cover the Commission's expenditure especially in connection with the exchange of astronomers from or to developing countries. Finally, an ad hoc working group of experts organized by Commission 46 of the IAU, agreed on the organization of an annual 'School of Young Astronomers'. A UNESCO grant provided for this purpose in 1966 could not be fully used owing to the short time available

ACTIVITY REPORT

xxiii

for the preparation of the curriculum. A substitute contract allowed the Union to allocate a scholarship to a student from a developing country towards his studies at a well equipped Observatory. The first UNESCO-lAD Summer School will open in Manchester, in 1967, under the direction cf Professor Z. Kopal. The General Secretary of the school is Dr J. Kleczek. This proposal was studied in great detail by the Executive Committee. The Committee would certainly have preferred that UNESCO, if it had been possible, should have assisted the normal activities of the Union, which have become rather burdensome. Other colleagues believe that a summer school is only justified as a pre-selection agent which would single out the most promising students for a longer stay at well-equipped observatories. Be it as it may, the results of the experiment will be carefully examined with regard to future policy. The IAU desires to maintain such contracts with UNESCO, to their mutual benefit. The present possibilities are likely to be fruitful, and the Union wishes to express its thanks and appreciation to UNESCO. Relations with ICSU and its organisms The ICSU is the organization on which the Union is most directly dependent: it transmits to the Union the UNESCO subvention (direct contracts not included) and co-ordinates the activity of Inter-Union Organizations. This help is valuable and necessary to the Union. Unfortunately the number of Unions within the ICSU increases, while the UNESCO subvention to ICSU remains essentially unchanged: thus the portion of the UNESCO subvention to the IAU is not likely to increase. The Union is responsible for travel grants for its representatives on the increasing number of Inter-Union bodies whose meetings are very frequent and held at places often very remote. While continuing to support the development of inter-disciplinary co-operation, the Union has therefore advocated efforts directed towards regrouping and greater efficiency. This was the Union's attitude in the re-organization of the Committees concerned with the physics of solar-terrestrial relationships; leading to the discontinuation of the IUCSTR and IUCI, the imminent termination of the activities of CIG and IQSY, and the formation of IUCSTP, whose principal objective will be the co-ordination of various activities. This recent action of the IAU is certain to contribute to a better inter-disciplinary co-operation in a domain of fundamental importance. The Executive Committee of the IAU, in its effort to strengthen the position of the Unions, opposed the development of independent national committees to deal with inter-disciplinary problems, as it is desired that national structures should conform to the inter-disciplinary character of international structures. The IAU participated with numerous Unions (IUTAM, IUGG, URSI) and Committees (COSPAR, IQSY) in the organization of Symposia (see above, page xxi). GENERAL CONCLUSIONS

The three years covered by the present report were difficult in many respects. It is certain, on the one hand, that the Members of the Union, and among them especially the Presidents of Commissions, Vice-Presidents, members of Organizing Committees of Commissions, members responsible for the organization of Symposia and Colloquia, and of numerous Special Services, representatives of the Union in different organizations, etc. have achieved admirable results. The Administrative Office of the Union, always anxious to keep within the narrow limits

XXlV

REPORT OF THE EXECUTIVE COMMITTEE

of the IAU budget, did its utmost to help Members in these efforts and thus to contribute to the promotion of the interests of Astronomy all the world over. In this respect attempts were made to simplify certain administrative procedures, whilst maintaining the high standard of the IAU publications. On the other hand, however, there is nothing perfect in this best of all worlds: the new IAU publication policy, adopted with the legitimate desire to improve the quality and distribution of IAU publications, is expensive. Moreover, its application, which calls for a narrow contact between the General Secretary in France, and the printers and publishers in the United Kingdom, met with difficulties in practice which were aggravated by a minor temporary crisis in the organization at the printers and by the change in the person of the IAU Assistant Secretary in 1966; the publications have been slow to come out of the press and their distribution has met with difficulties. This, naturally, puts a strain on the relations between Administration and Members. Moreover, the sales have, so far, been unsatisfactory. In this connection, it should be emphasized that these relations with Members are based on a rather biased tradition. The IAU is one of the few international organizations having individual members. Members of the Union pay no contribution and no fees; yet, steadily increasing in number, they obtain, free of charge, publications ever ampler in volume; and they have the benefit of the numerous services organized and financed by the Union, and of the scientific contacts the Union facilitates. Moreover, the contributions of Adhering Organizations are modest compared with the sums their countries spend on Astronomy in their own countries, especially in this age of the rapidly-developing Radio-Astronomical and Space Sciences. The highest single annual national contribution is equal to only five times the return fare between North America and Europe, and corresponds to the cost of printing and distributing two issues of the Information Bulletin, which is also equal to the IAU contribution to the costs of a single Symposium! There are only two possible solutions. An attempt may be made to introduce more financial justice by relaxing the generous tradition of the Union and having Members pay a contribution; IAU publications being sold to Members and not distributed free of charge (this measure is already being put into operation); observatories assisting the Union by financing part of the Specific Projects of the Commissions. Or, if a certain liberality is to be maintained, especially as regards membership and Specific Projects, the Adhering Organizations must agree to accept an increase in the contributions that they pay (see below, Appendix I, page xli). The Executive Committee is convinced that there is no other alternative, and that the traditional generosity of the IAU budgets is obsolete. Moreover, it is certain that the growing 'gigantism' of the Union will soon have to give way to a new structure. It will be the task of the future Executive Committee to work towards this change.

APPENDICE I. RAPPORT FINANCIER (See English version on page xli) A.

INTRODUCTION

Conformement a la politique financiere introduite en I961, le Comite Executif presente aux Membres de l'UAI un seul 'Compte Resume des Recettes et Depenses' couvrant la periode du I janvier I964 au 31 decembre I966. Toutes les sommes ont ete converties en dollars U.S.; le taux de change adopte, pour suivre les regles de !'Unesco, a ete le suivant: £sterling: $2·8o

$ U.S.: 4'90 francs franc;ais

Certaines operations (virements d'un compte a un autre, remboursements de sommes excedant les besoins) ont ete faites au change du jour par les banques: il s'ensuit des erreurs de change. Le compte resume a ete obtenu a partir des neuf comptes (un pour chaque devise, et un par an) etablis a partir des cahiers. Ceux-ci seront disponibles pour examen par le Comite des Finances. Ils ont ete examines et certifies corrects par les experts comptables ayant travaille pour I' Union. Le present rapport se termine (ci-dessous page xxxix) par la declaration d'expertise pour !'ensemble des comptes des trois annees en consideration, suivi par des suggestions relatives au budget des annees suivantes. Le rapport ci-apres comporte, en commentaire du compte resume, des notes necessaires a sa comprehension complete point par point. Les sommes dues a la fin de l'exercice I966, ou les recettes correspondant a des paiements arrieres pour la periode I96I-I964, sont notamment indiquees dans chaque cas. Contrairement a ce qui s'est passe dans la periode I961I964, ces sommes ne sont pas negligeables, en raison de la modification importante apportee au systeme des publications de l'Union; nous avons consacre un appendice detaille a cette question. Le rapport enfin est conclu par une mise en garde serieuse, la situation financiere etant en effet particulierement difficile, et par des propositions relative au budget de I967 et des annees I968, I969, I970. B.

COMPTE RESUME DES RECETTES ET DEPENSES Recettes

1. Cotisations des pays adherents. La Xle Assemblee Generale de l'UAI, a Berkeley, a decide de fixer l'unite de contribution a 6oo francs-or pour 1962 et les annees suivantes. On rappelle qu'un franc-or est egal a o,2903225 gramme d'or fin, eta o,3266 dollar. L'unite de cotisation est done de $195·96. A la suite de la modification des statuts adoptee par la XIIe Assemblee Generale, il a ete demande aux Pays Adherents de choisir une nouvelle categorie d'adhesion, conformement au nouvel article 4 des Statuts, tel qu'il figure dans le Volume XII C des Transactions. Le nombre total d'unites de contribution a done augmente nettement, d'une fac;on qui n'a toutefois pas correspondu entierement aux espoirs du Comite Executif de la periode 196I-I964, qui avait suggere la modification des Statuts, notamment dans ce but. II est a noter qu'en I966 un effort particulier a ete fait, avec succes, pour le recouvrement des cotisations dues, et pour un choix meilleur, dans certains cas particuliers, de la categorie d'adhesion. Au 31 decembre 1966, six pays sont en dette vis-a-vis de l'Union (soit au total 20 unites de contribution dues). Un pays en revanche s'est deja acquitte du montant (6 unites) de la cotisation 1967. Lecompte d'un autre pays est crediteur de $If0'f0.

XXV

XXVl

RAPPORT DU COMITE EXECUTIF COMPTE RESUME DES RECETTES ET DEPENSES

(Exprime en U.S. Dollars) Pour la periode I964-I966

Recettes U.S. Dollars U.S. Dollars I .

Cotisation des Pays Adherents Nombre d'unites

Dues

2.

3. 4·

5·

6.

7·

RefUeS

I963 et anterieures I6 I3 I964 I26 I I9 I965 I52 I46 I966 I57 ISO (I967) 0 7 Vente des Publications Abonnements aux Publications de l'UAI Agios crediteurs bancaires Comptes courants .. Comptes bancaires ..

8s 34I"9I n 882·78 4469"79 3I9'54 8 5I3"35

Subventions de l'UNESCO, accordees par l'intermediaire de l'ICSU Imputation: Symposiums, publications I964 I965 I966

I4 ooo·oo I4 ooo·oo I4 ooo·oo 42 ooo·oo

Contrats avec I' UNESCO Participation a I' organisation du Symposium no. 23 Participation a I' organisation du Symposium no. 25 Echange des Astronomes (Commission 38) Ecole d'Ete (organisation) (Commission 46) Bourse d'etude- I966- (Commission 46)

I I54·86 4 499"46 2 ooo·oo I 3o6·oo 3 ooo·oo

Divers Subvention de l'ICSU pour l'IUCSTR Participation de l'URSI a I' organisation du Symposium no. 20 Remboursements divers - ala Commission 38 - de la subvention a l'IUCI - du fonds de reserve du Bureau des Telegrarnmes

3 072"04 I8o·oo 2 267"04

Total des recettes e.ffectives 8.

Execs des Depenses sur les Recettes ..

h73 771"17 19 700"84 SI93 472"01

Etat des Comptes Bancaires au I janvier I 964 -en banque (epargne) -en banque (comptes courants) -en petite caisse

62 730'84 46 798·8I 0"37

h09 530"02

RAPPORT FINANCIER

xxvii

COMPTE RESUME DES RECETTES ET DEFENSES

(Exprime en U.S. Dollars) Pour Ia periode I964-I966

Depenses I. 2.

Bureau Administratif Cotisation a I'ICSU ..

3· 4·

Depenses de Fonctionnement des Commissions Entreprises specifiques des Commissions approuvees par I' Assemblee Generate ..

5·

Assemblees Generales- Hambourg, aout I964 (a) Membres du Comite Executif (frais de voyages) (b) Presidents des Commissions (frais de voyages) (c) jeunes astronomes (frais de voyages) (d) divers -Prague, aout I967 (d) divers (voyage aPrague du Secretaire General)

6.

Frais d'impression des Publications editees par l'UAI

7.

Reunions du Comite Executif (a) Nice, septembre I965 (b) Prague, septembre I966 ..

U.S. Dollars U.S. Dollars 30 23I·6o I 490"74 452"29

I 7I4·8o 7 2I9"4I 5 044"7I I 582·54 I33"26 IS 694"72 s6 7I2·oo 3 092"36 2 I30"49

5 222·85

8.

Organisation des Symposiums et Colloques de l'UAI et Participation ad'autres reunions scientifiques

20 OI4"30

9·

Publications des Symposiums (lorsque l'editeur n'est pas l'UAI)

I3 o88·36

Io.

Commissions Interunions- Comites de l'ICSU, etc

I I.

Autres frais de representation

I2.

Entreprises Specifiques approuvees par le Comite Executif

I3.

Programme sous contrat direct avec !'UNESCO (a) Commission 38, Echange d'Astronomes (b) Commission 46, Organisation des Ecoles d'ete .. (c) Commission 46, Bourse d'etude

I4.

7 47J"II 8s8·oo 350"00 2 ooo·oo I 306·24 2 ooo·oo

Total des depenses effectives Difference de change dans les virements internes Total

Exces des Depenses sur les Recettes effectives Soldes au 3 I decembre I 966 (a) existant en banques (epargne) (b) existant en banques (comptes courants) (c) existant en petite caisse ..

h93 472"0I

7I 244"I9 IS 5I8"92 66·o7 $I09 530"02

xxviii

RAPPORT DU COMITE EXECUTIF

2. Ventes des publications. En raison de Ia complexite des comptes, il est difficile de donner un bilan par ouvrage vendu. Mais nous avons tente, en un appendice separe, de presenter un bilan relatif aux operations (recettes et depenses) liees aux publications de l'UAI, que l'UAI ait ete ou non l'editeur. 3· Abonnements aux publications de l'UAI. Une experience a ete tentee, a partir de l'annee 1963: il s'agissait de distribuer les publications de l'UAI contre le versement d'une souscription forfaitaire, a toutes les institutions de Ia 'liste de distribution'. La difficulte du recouvrement, et Ia complexite administrative de ces operations ont conduit a supprimer ces abonnements des rg66. Voir appendice relatif aux Publications, page lv. 4· Agios crediteurs bancaires. Les interets sur les comptes d'epargne ont ete laisses a ces comptes, et incorpores aux capitaux deposes. De plus, le compte courant, en francs fran 30 lines per mm over field of 30 mm diameter. Background so low that exposures of about one hour are practicable with transfer optics which give a speed gain of about I oo times. Probably the outstanding defect of these tubes is the presence of bright scintillations, as appears to be the case in all tubes of this type. These spurious signals produce a background which would be objectionable in high quality images. Investigations continue into the causes and possible means of removal of these signals. Similar three-stage cascade tubes are being made with S.I or 8.20 primary photocathodes. T. Dunham, Jr., Mt Stromlo Observatory

A five-stage secondary-emission image intensifying tube has been mounted in the coude spectrograph of the 74-inch (I88 em) telescope, at the focus of the I2o-inch (3os em) camera. The optical axis of the camera is 26 inches (66 em) above the heavy steel frame of the instrument, and measurements show that distortion of the field of the 400-gauss permanent magnet in which the tube is mounted is insignificant. The tube was carefully selected by 2oth Century Electronics to have a very low dark count (less than so scintillations cm- 2 s-1). The resolving power, measured with a Baum microprojector is 2s-3o line-pairs per mm. The display at the output was photographed with a transfer lens on stationary 3S mm film, and also on moving film to record individual scintillations (14). Due to the wide range in brightness of the scintillations, granularity is severe unless the aperture ratio of the transfer system is held to f/8 to f/ I I. Under these conditions the image tube showed only a moderate gain over direct photography. The moving film scintillation counting technique, however, allows use of the full aperture {f/I'9) of the transfer system. Performance is being compared with that for the stationary film technique. A Fabry-Perot etalon in the collimated beam of the spectrograph has been provided with mechanical scanning, synchronized with a precision grating drive, so that approximately so fringes can be recorded simultaneously with the image tube (15). The spectra of stars to 4·0 magnitudes have been recorded at I·8Afmm in 20 minutes. M. J. Smyth and P. W. J. L. Brand, Royal Observatory, Edinburgh, Scotland

A Lenard window image tube (Spectracon) constructed at Imperial College is being evaluated as a spectrophotometric detector, in the Cassegrain spectrograph of the 36-inch (9I em) reflector (16). A suitable environment for the image tube on the telescope, free from electrical discharge due to damp air, has been achieved by the use of airtight compartments for the high voltage components, and a thermo-electric cold trap between the spectrograph camera and the tube cathode; and the image shift caused by motion of the tube with respect to the geomagnetic field had been investigated. The equivalent quantum efficiency of the tube is being determined, as a function of absolute spectral sensitivity, spatial frequency response, and granularity noise. Granularity is derived from computer analysis of density measurements made with a digitized microphotometer. A calibrated tungsten lamp is used for sensitivity determination, and the modulation transfer function is also being studied. The methods being developed will be immediately applicable to other types of image tube, and to conventional photography. The tube is being used in a stellar spectrophotometric programme that is also being carried out by direct photography, thus enabling a comparison of photometric effectiveness to be made. D. J. Bradley, Physics Dept., Queen's University, Belfast 1. The performance of image tubes for recording high resolution spectrograms has been evaluated (17). Tubes tested include a five-stage T.S.E.M. tube (18), single and three-stage

118

COMMISSION 9

phosphor-photocathode tubes (19) and a Lenard window tube (20). For spectroscopy in general the Lenard window tube has outstanding signal-to-noise performance with, in addition, the great advantage of a linear density-exposure relationship. Signal induced background, at an overall voltage of 40 kV, was found to be negligible and absorption lines were faithfully recorded. Operating with a voltage of only 26 kV, the signal-induced background and noise of the T.S.E.M. tube, and the wide spread in the multiplication factor for individual photoelectrons, resulted in such a decrease in the effective signal-to-noise ratio in the recorded image as to make it unsuitable for quantitative spectroscopy. The signal-to-noise performance of the cascaded phosphor-photocathode tube was much superior to that of the T.S.E.M. tube. 2. A single stage magnetically focused image converter with a 'Spectrosil' window, S-9 photocathode and a phosphor screen output has been employed to record Fabry-Perot interferograms of .,\ 1849A of Hg 1 for the first time (21). The performance of the image tube at this wavelength was entirely satisfactory. Cs-I photocathodes have been tested in photocells before employing them in solar blind tubes. 3· A development channelled image intensifier (22) has also been tested for spectral recording. With channels o·s mm diameter and an effective resolving limit of 1-2 line pairs per mm, a spectral resolving power of 104 was obtained (23) for a camera focal length of 30 em, employing the second ring of a Fabry-Perot etalon with an effective finesse of 10. Such a combination of interferometer-channelled image intensifier would be particularly useful for rocket and satellite spectroscopy of extended sources. W. A. Hiltner, Yerkes Observatory, University of Chicago, U.S.A.

Experimental work on image tubes has been discontinued here, principally because of lack of time, certainly not because of any lack of faith in the electronographic process. When opportunity presents itself, I want to apply a system to astronomical research. Something over one year ago Drs Kron and Kent Ford and I intercompared several methods of image intensification. Our conclusion at that time was that the gain of electronography over classical photography in the blue is set at near one times the quantum efficiency of the photocathode in percent, in agreement with measurements of the quantum efficiency of photographic emulsions, and probably slightly less for the cascaded image tube although any loss is essentially compensated for by easier and more efficient operation of the cascaded tube. During the past year we built a spectrograph for the cascaded image tube. It has a .f/2 Schmidt camera with field flattener. We used it on the McDonald 82-inch reflector for the observation of quasi-stellar and Haro-Luyten objects. Spectrograms of 2ooAjmm were obtained of 18·4 magnitude objects (about the limit of visual setting) in about two hours when unbaked Kodak IIa-0 emulsion was used (24). The spectrograms were quite satisfactory for radial velocity measurements. We will use the spectrograph again at the next opportunity. Dr W. Kent Ford, Carnegie Institution of Washington, U.S.A.

The Carnegie Image Tube Committee, with support from the National Science Foundation, has sponsored the development of a two-stage, cascaded image intensifier at RCA. The tubes have multialkali photocathodes, 38 mm diameter useful areas, and provide information gains of 10 over conventional photography. Several dozen tubes have been fabricated by RCA for the Carnegie Committee. These are being distributed with the necessary auxiliary equipment to various observatories. Thus far, sets have been installed at Yerkes, Kitt Peak, Mt Wilson, Lick, Lowell, University of Texas, Naval Observatory, Dominion Astrophysical, Palomar, University of Arizona, and Mt Stromlo.

INSTRUMENTS

119

Dr R. E. Danielson and colleagues, Princeton University Observatory, U.S.A. RCA engineers and members of the Princeton Observatory are currently completing tests of an image orthicon camera system for use on the Stratoscope II Program (25, 26). Uncooled high resistivity glass target tubes with o·oox mesh spacing have yielded integration periods in excess of ten minutes. Sensitivity comparison, using stellar sources, indicates at least a factor of ten improvement in speed over 103a-G film used in Stratoscope II. Tests now in progress, operating the image orthicon in the 'isocon' mode, indicates further improvement. Analysis of the data also indicates good linearity of exposure versus the volume of the video pulse. Within the next year the Princeton Observatory expects to operate a SEC Vidicon, built by Westinghouse, comparable in image and target size to the 3-inch (7·6 em) image orthicon, under the similar test conditions. The SEC Vidicon tests will also involve cooled operation and spectral readout.

M. F. Ingham, the Department of Astrophysics, Oxford Mr J. E. Beckman investigated the usefulness of image intensifier tubes to astronomy (27). Two types of tube were evaluated: an English Electric Valve Co. transmission secondary emission tube (the so-called Imaging Photomultiplier) and one of the Lenard window type. For both tubes the gain, spectral sensitivity, resolution and dark emission were measured. The distortion introduced by the secondary-emission tube was also studied. Finally, the English Electric tube was used in conjunction with the solar spectrograph to obtain high dispersion (4·2 mmf A) spectra of Venus and Jupiter. With these spectra it was possible to place an upper limit on the abundance of oxygen in the atmosphere of Venus and to measure the abundance of hydrogen in the atmosphere of Jupiter. At the Atomic Energy Research Establishment at Harwell, Mr A. V. Hewitt of this Department, and Dr W. N. Charman have been conducting similar experiments with an E.M.I. cascade tube (28) which they will shortly use with the 30-inch (76 em) telescope at the Royal Greenwich Observatory Herstmonceux for experiments in stellar spectroscopy.

Dr R. J. Davis, Project Celescope, Astrophysical Observatory, Smithsonian Institution, Cambridge, U.S.A.

A special-purpose television camera tube (the Uvicon) and associated optics and digital television system (the Celescope) have been developed to meet the Smithsonian Astrophysical Observatory's requirement for measuring the ultraviolet brightnesses and the positions of a very larg~ number of objects throughout the sky. The wavelength region of interest, from xooo to 30ooA, is observable only from above the Earth's atmosphere, thus precluding our utilization in this wavelength region of the well-developed photometric techniques used in ground-based astronomy. The unique characteristic of the Uvicon tube is its combination of accurate photometric measurement ability, ultraviolet sensitivity and ruggedness of construction. In order to achieve the necessary photometric accuracy, range and sensitivity the Uvicon incorporates a secondary electron conduction (SEC) target to amplify and store the photoelectric image from the photocathode. The tube is available with two photocathode materials: caesium iodide, which is insensitive to wavelengths longer than about zoooA, and caesium telluride, insensitive to wavelengths longer than about 3oooA. The short wavelength cut-off is that of the lithiumfluoride face-plate (xosoA at room temperature). The basic design of the tube allows considerable flexibility in regard to its geometrical and electrical configuration; in the case of the Uvicon, the face-plate is incorporated as a refractive element in the optical design of the telescope system, and both the imaging section and the electron scanning gun utilize only p

120

COMMISSION 9

electrostatic focusing and scanning techniques. The Uvicon was developed and manufactured by Westinghouse Electric Corporation under contract to the Smithsonian Astrophysical Observatory. Another Westinghouse tube, an LEM camera tube developed for the Lunar Excursion Module, if modified to provide ultraviolet sensitivity, would provide improved performance over the existing Uvicon configuration. In order to achieve full photometric accuracy, all operating parameters of the tube must be very carefully controlled- including the timing of the voltage variations required for operating the tube. In this way, we have been able to achieve a photometric precision of ± 5% in the measurement of laboratory light sources during calibration of the Celescope experiment. Our investigation has also indicated that this accuracy can be improved, by a significant but unknown amount, by more careful control of operating voltages and sequences. In order to achieve full photometric accuracy, the Uvicon must be calibrated under conditions as near as possible to those under which it is to be used. The transfer function is far from linear, and varies from one part of the raster to another. Variations with temperature are less severe, but must also be determined by individual calibration if the tube is to be used outside of the range + 30° to + I0°C. There is, fortunately, no reciprocity failure, total exposure being exactly proportional to the product of intensity and exposure time between one and 150 seconds. Typical operating characteristics of the Celescope system, utilizing the Uvicon, are as follows: Photocathode Quantum Efficiency Spectral passband Photometric Range Photometric accuracy Field of view* Positional measurement accuracy* Limiting resolution*

A-Type

D-Type

3% at 2oooA 1050 to 32ooA 6 X 10-16

8% at 14ooA 1050 to 19ooA to 6 x 10-12 ampere

±5% inch (2·8 em) diameter circle at photocathode o·o1 inch (o·25 mm) at photocathode o·o1 inch (o·25 mm) at photocathode I" I

*These characteristics were not critical to the Celescope experiment, and can fairly easily be improved if required for other experiments.

In order to take full advantage of the speed and accuracy with which a television system such as this can generate data, the signal must be analysed by a high-speed digital computer. We attain our highest accuracy by using digital techniques to control the Uvicon anti digitize its output signal before transmission. By generating our video signal in digital form, it can be recorded on magnetic tape in a format acceptable as input to a digital computer. The equipment and techniques required for operating the Uvicon as a stellar photometer have been developed by Electro-Mechanical Research Inc., under contract to the Smithsonian Astrophysical Observatory. This research has been supported in part by Contract NAS 5-1535 from the National Aeronautics and Space Administration.

L. W. Frederick, Leander McCormick Observatory, University of Virginia, Charlottesville, U.S.A. The mica window S-1 tube has been completely remounted so that it can be operated with the potential on. The system is in excellent operating order and is being used to continue the late-type stellar studies previously reported. Some 380 additional plates have been taken on the new McCormick reflector primarily by George Lockwood, a graduate student here.

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A cascade S-1 image intensifier converter is currently being mounted and will use a circulatory slush cooling system. This tube appears to be an excellent tube.

An eight-foot non-magnetic optical bench has been fabricated to assist in the aligning and testing of our equipment. A Baum type pattern projector has been purchased from Hobbs, Ltd. to assist in the evaluation of tubes. Our primary objective is to apply the Carnegie tubes to astronomical problems. Hence, we do very little experimental and development work. BIBLIOGRAPHY

I. 2. 3· 4· 5·

6. 7· 8.

9· IO. II,

u.

13. 14. 15. x6. 17. x8. 19. 20. 21. 22. 23. 24. 25.

Lallemand, A., et al. 1966, C. r. Acad. Sci. Paris, 262, 838. Duchesne, M. 1965, J. Phys., 26, n7. Duchesne, M., Feissel, M., Guinot, B. 1965, Notes Inj. Publ. Obs. Paris, fasc. 26. Hezard, C. 1965, These de 3eme cycle, Paris. Combes, M. 1966, Contribution a l'etude de !'atmosphere de Jupiter, These de 3eme cycle, Paris. 1966, Adv. Electronics Electron Phys., Academic Press, 22A, 76I. Livingston, W. C., Lynds, C. R., Doe, L. A. I966, Recent Astronomical Research Utilizing a High Gain Image Intensifier Tube. Adv. Electronics Electron Phys., ed. L. Marton (New York and London: Academic Press), 22B, 705. Lynds, C. R., Stockton, A. N., Livingston, W. C. I965, New Spectroscopic Observations of Quasi-Stellar Sources, Astrophys. J., 142, 1667. Lynds, C. R., Stockton, A. N. 1966, The Large Redshift of the Quasi-Stellar Source I n6 + 12, Astrophys. J., 144, 446. Lynds, C. R., Hill, S. J., Heere, K., Stockton, A. N. 1966, New Spectroscopic Observations of Fourteen Quasi-Stellar Sources, Astrophys. J., 144, 1244. Thaddeus, P., Clauser, J. F. I966, Cosmic Microwave Radiation at 2·63 mm from Observations of Interstellar CN, Phys. Rev. Letters, x6, 819. Livingston, W. C. Adv. Electronics Electron Phys., ed. L. Marton (New York and London: Academic Press), 23, in press. McGee, J. D., Khogali, A., Ganson, A., Baum, W. A. 1966, Adv. Electronics Electron Phys., Academic Press, London, 22A, I I. McGee, J. D., Khogali, A., Ganson, A. I966, Adv. Electronics Electron Phys., Academic Press, London, 22A, 3 I. Jeffers, S., McGee,]. D. 1966, Adv. Electronics Electron Phys., Academic Press, London, 22A, 41. McGee, J. D., Airey, R. W., Aslam, M., Powell, J. R., Catchpole, C. E. 1966, Adv. Electronics Electron Phys., Academic Press, London, 22A, II3. Dunham, T. 1960, J. opt. Soc. Amer., so, 1129. Dunham, T. 1962, Astr. J., 67, 575· Brand, P. W. J. L., Smyth, M. J. 1966, Use of a Lenard-window image tube for astronomical spectrophotometry, Adv. Electronics Electron Phys., 22B, 741. Bradley, D. J., Bates, B., Juulman, C. 0. L., Majumdar, S. 1964, Appl. Opt., 3, 1461. Wilcock, W. L., Emberson, D. L. Weekley, B. 1960, Nature, x8s, 370. McGee, J. D., Catchpole, C. E. 1962, British lEE Conf. Rept., Series 5, p. I82. McGee, J. D., Wheeler, B. E. 1962, Adv. Electronics Electron Phys., Academic Press, London, x6, 47· Bradley, D. }., Bates, B., Juulman, C. 0. L., Majumdar, S. 1964, Nature, 202, 579· McGee,}. D. 1961, Rep. Progr. Phys., 24, 167. Bradley, D. J. I966, Sciences et Industries Spatiales, no. 7/8. Hiltner, W. A., Cowley, A. P., Schild, R. E. I966, Pub!. astr. Soc. Pacij., 78, 464. Cope, A. D., Luedicke, E. I965, Adv. Electronics Electron Phys., Academic Press, London, 22A, 175.

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1966, Adv. Electronics Electron :z6. Flory, L. E., Pike, W. S., Morgan, J. M., Boyer, L.A. Phys., Academic Press, London, :z:zB, 885. 27. 1966, Adv. Electronics Electron Phys., Academic Press, London, :z:zA, 369. :z8. 1966, Adv. Electronics Electron Phys., Academic Press, London, :z:zA, 101. APPENDICE 2. GROUPE DE TRAVAIL SUR LA QUALITE DES IMAGES ET LE CHOIX DES SITES

(prepare par J. Rosch, president) La denomination de ce groupe pourrait, a Ia rigueur, ne mentionner que le Choix des Sites, carle role de Ia qualite des images dans presque tousles genres d'observation est suffisamment reconnu maintenant pour que toute operation de prospection en tienne compte, parmi un certain nombre d'autres facteurs; et par contre, toute etude sur Ia qualite des images est destinee, directement ou indirectement, arendre plus efficace Ia recherche des sites les meilleurs. Les methodes appliquees a Ia selection des sites ne se codifient que lentement, sans doute parce qu'en general, jusqu'ici, le temps disponible pour chaque operation a ete limite par Ia hate de passer a !'implantation de l'observatoire projete. Cet etat de choses a aussi pour consequence que faute de conclusions de portee generale certaine, Ia litterature est assez pauvre en publications dans ce domaine, et les resultats des prospections restent souvent consignes dans des documents peu diffuses en dehors des organismes responsables des operations. Le present rapport sera done limite aux travaux parvenus a Ia connaissance de !'auteur et ne saurait pretendre etre exhaustif. La delimitation preliminaire des regions propres a !'implantation d'un observatoire de programme determine s'oriente progressivement vers une utilisation plus approfondie des donnees meteorologiques et des quelques principes dont Ia validite se precise, notamment !'interet des altitudes d'au moins 2ooo metres pour Ia photometrie, !'importance significative de Ia faiblesse des ecarts des temperatures diurne et nocturne, l'avantage des sommets isoles pour Ia stabilite de Ia temperature nocturne, le role nefaste des inhomogeneites dans les couches voisines du sol. La publication d' etudes de ce genre sur des regions limitees, telles que celle de Hansen et al. pour les lies Hawa1 (z), celle qui paraitra prochainement sur les campagnes de l'ESO en Mrique du Sud (:z) ou celles en cours en France et en Espagne, et au Bresil, constituera, par confrontation avec les resultats obtenus dans les observatoires futurs, une source precieuse pour la comprehension des phenomenes. L'un des problemes les plus irritants dans les debuts d'une prospection reste !'evaluation de la nebulosite nocturne. J. Saissac a tente, pour le Sud de la France, de dresser une carte du nombre d'heures utilisables en partant du nombre de jours de pluie releve dans les stations seulement pluviometriques dont le reseau est dense, et des correlations etablies entre ce nombre et le nombre d'heures utilisables pour les stations meteorologiques completes qui soot beaucoup moins nombreuses (3). Pour un travail plus direct, R. de Freitas-Mourao a realise, selon les suggestions faites au Symposium no. 19 de l'UAI, une chambre 'tout-ciel' susceptible d'une autonomie de plusieurs jours et permettant, sur des images exposees environ 1 minute, de mesurer l'absorption par les magnitudes limites atteintes (4). Apres le nombre d'heures photometriquement utilisables dans l'annee, !'element essentiel (a part le point particulier de Ia diffusion atmospherique pour les observations de Ia couronne solaire) est Ia qualite des images. Devant Ia difficulte pratique (surtout en campagne) d'obtenir un spectre de Fourier a deux dimensions des deformations de Ia surface d'onde, on se contente d'un simple nombre, dont on cherche cependant une valeur objective attachee a une interpretation bien definie. C'est le but de l'ASM (Automatic Seeing Monitor) de Babcock (S) ou de la lunette polaire de Walker (6). Dans le premier cas, on obtient directement une mesure

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de !'agitation, done de la fluctuation de la direction de la normale ala surface d'onde. L'ASM a ete largement utilise au Chili (Cerros Tololo, Morado, Pachon, La Silla), ou Irwin a notamment etudie la variation de la quantite mesuree avec la distance zenithale (7), ainsi qu'au Mt Palomar et a Siding Spring (Australie) (8, 9). Dans le cas de la lunette polaire, on pourrait obtenir la meme donnee, mais moyennant un procede d'exploitation quantitative des trainees photographiques ou une traduction photoelectrique directe de !'agitation. Un travail dans ce sens est en cours a l'Observatoire du Pic du Midi. Une telle estimation de la valeur d'un site, quant a la qualite des images, repose sur le postulat que les spectres de Fourier des deformations des surfaces d'onde reelles appartiennent a une famille a un seul parametre. Le moyen le plus simple de s'assurer de la legitimite de la prevision de la qualite des images dans un grand instrument a partir de mesures d'agitation est d' etablir empiriquement une correlation entre les deux phenomenes; c' est ce qui a ete entrepris a l'Observatoire du Pic du Midi par des mesures quasi-simultanees d'une part, au moyen de l'imagemetre, du diametre equivalent de l'image d'une etoile donnee par un reflecteur de 105 em, d'autre part, au moyen du chercheur du meme instrument, de !'agitation fournie par des trainees photographiques. Une etude observationnelle des correlations s'impose encore plus si l'on veut prevoir une qualite d'image d'apres des mesures de fluctuations ou de gradients de temperature dans les premieres dizaines de metres de !'atmosphere au-dessus du sol. Un travail de ce genre fait a l'Observatoire de Haute-Provence (xo) montre bien une correlation limite entre les fluctuations a une hauteur egale a celle de l'ouverture du telescope de 193 em et le diametre estime de !'image observee dans ce meme instrument, du moinsjusqu'a une certaine valeur de ce diametre; mais on trouve aussi des diametres de !'image plus grands que ceux qui suivent la correlation, ce qui revele des deteriorations dans des couches plus elevees que la prise de temperature. Un tel resultat ne peut que confirmer que la solution la plus sure consisterait a faire un prelevement optique a un niveau eleve aussi proche que possible de celui auquel se trouvera, en moyenne, l'ouverture du futur instrument. REFERENCES

Hansen, R. T., Hansen, S. F., Price, S. 1966, Pub!. astr. Soc. Pacij., 78, 14. Pub!. Obs. austr. Europeen (a paraitre). 3· Saissac, J. 1966, Documents du Comite National Franc;ais d'Astronomie. 4· Freitas Mourao, R. R. de These, Universite de Paris (a paraitre). S· Babcock, H. W. 1963, Mt Wilson and Palomar Observatories. 6. Harlan, E. A., Walker, M. F. 1965, Publ. astr. Soc. Pacif., 77, 246. 1966, Astr. J., 71, 28. 7· Irwin, J. B. 8. A. Rep. Dir. Mt Wilson Palomar Obs., 1963-64, et 1964-65. 9· 1966, CARSO Rep., Carnegie Institution of Washington. IO. Bourlon, Ph. 1966, Documents du Comite National Franc;ais d'Astronomie. u. Bateson, F. M. 1964, Publ. Univ. Pennsylvania, IO, 1-139. I2. Matsushima, S. 1964, Publ. astr. Soc. Pacif., 76, 224. IJ. Hogg, A. R. 1965, Mt Stromlo Publ., AST. 65/169. I.

2.

10. COMMISSION DE L' ACTIVITE SOLAIRE PRESIDENT: Dr Z. Svestka, Astronomical Institute of the Czechoslovak Academy of Sciences, Ondrejov, Czechoslovakia. VICE-PRESIDENT: Dr J. T. Jefferies, Hawaii Institute of Geophysics, 2525 Correa Road, University of Hawaii, Honolulu, Hawaii 96822, U.S.A. SECRETAIRE: Dr A. D. Fokker, University Observatory 'Sonnenborgh', Servaas Bolwerk 13, Utrecht, the Netherlands. CoMITE n'ORGANISATION: R. G. Giovanelli, K. 0. Kiepenheuer, W. 0. Roberts, J. Rosch, A. B. Severny, Henry J. Smith, M. Waldmeier. MEMBRES: Allen, Aly, Athay, d'Azambuja (L.), Babcock (H. W.), Balli, Bell, Belorizky, Billings. Bogorodsky, Bonov, Bray, Bruckner, Bruzek, Bumba, Cardus, Cimino, Coutrez, Dezso, Dizer, Dodson-Prince, Dollfus, Dubov, Dunn, Elste, Ferraro, Fracastoro, Gaizauskas, Gleissberg, Gnevyshev, Gnevysheva, Godoli, Goldberg, Gullon, Gurtovenko, Howard (R. F.), Jensen, Karimov, Kleczek, von Kluber, Kopeck)\ Krat, Kristensen, Krook, Kunzel, Lehnert, Leighton, Letfus, Loughhead, Macris, Mathias, Mattig, Maxwell, McKenna, Menzel, Mergentaler, Michard, Mitra (A. P.), Miyamoto, Mohler, Moiseev, Moreton, Muller (H.), Mustel, Nagasawa, Nedungadi, Newkirk, Notuki, Ohman, Orrall, Peeker (Ch. W.), Pick, Popovici, Prokofiev, Ramanathan, Razmadze (T. S.), Richardson (R. S.), Ringnes, Saito (K.), Schluter, Schroter, Servajean, Shapley (A. H.), Shaposhnikova, Shklovsky, Simon (P.), Sitnik, Slonim, Smerd, Smith (E. v. P.), Stepanov, Steshenko, Suemoto, Tandberg-Hanssen, Trellis, Tuominen, Valnfcek, Wild (J. P.), Wlerick, Xanthakis, Zirin, Zwaan. The research activity in the field of Commission 10 has been enormously increasing as one can easily observe when comparing the present list of references with the Draft Reports of the preceding three-year periods. Therefore, some limitation of the contents of the Draft Report is necessary. We have not included any paper presenting only observations without any discussion of them and as the solar-terrestrial physics is concerned, only those papers are included, which contribute to our knowledge of the Sun and its wave and particle emission. That means that we have not mentioned here the numerous papers which treat the influence of the solar activity on the terrestrial magnetosphere, ionosphere and troposphere, unless some information on the problems of solar physics or solar cyclic variations can be deduced from them. We have included all the remaining papers concerning solar activity published since the beginning of 1964 and very few papers which appeared in 1963 and clearly could not be included into the last Professor Severny's Report. Most of the members of the Organizing Committee and many members of the Commission participated in preparing the Draft Report. Particularly: Section 6 is based on the report on sunspots prepared by W. Mattig, section 8 on the report on prominences prepared by J. T. Jefferies, section 9 on the report on the active corona prepared by J. Rosch, and section 10 on the report on active radio phenomena prepared by A. D. Fokker. E. v. P. Smith substantially contributed to sections 11, 12, and 13. A. B. Severny's report on magnetic field measurements has been used extensively when preparing sections 4, 6, and 7.2. A. B. Severny and N. V. Steshenko also provided me with a list of references and abstracts of papers published in the U.S.S.R. and S. Nagasawa informed me in a similar way about papers published in Japan. A detailed report on terrestrial effects of solar activity prepared by C. Sawyer unfortunately arrived too late to be included in this Report. My thanks are due to all these contributors as well as to all other solar physicists who have provided me with useful information on the recent progress of their work. 125

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International projects

During the reported period four international projects were organized, closely connected with problems of solar activity: International Years of the Quiet Sun (IQSY) started on I January, I964 and lasted for two years. From the point of view of solar physicists, the main aims of IQSY were (I) to maintain a complete patrol service during the period of the solar minimum, and (2) to profit by observations of fairly isolated active processes on the Sun both as the study of solar active regions and the solar-terrestrial physics are concerned. The study of isolated active regions was the main purpose of the Cooperative Study of Solar Active Regions (CSSAR), organized by R. Michard for half a year during the IQSY period, from I April to 30 September I965. Its main aim was to study the development of active regions without any disturbing effects of adjacent solar activity, with particular emphasis on the final decay of local magnetic fields. Commission IO also organized the Proton Flare Project (PFP) from I May to 30 September, I966, with P. Simon as the Chief Coordinator. Very successful proton flare forecasts enabled to get many data on proton flares of 7 July and 2 September, I966, and on the associated active regions. The project on 'Rapid Variations of Solar Magnetic Fields' organized by V. A. Krat, had many features similar to CSSAR and PFP. Final results of these projects had not yet been known when this Draft Report was submitted for press. It is supposed that the scientists responsible for these projects give general information on them during the Prague Assembly and some of the results will be reported at the IAU Symposium on the Structure and Development of Solar Active Regions in Budapest, in September I967. I .2.

Books and Symposia

Three important books, of general interest for those working in the field of solar activity, appeared during the reported period: A monograph about sunspots by Bray and Loughhead (1964) gives a description of a wide range of sunspot phenomena and their interpretation. Kundu (1965a) published 'Solar Radio Astronomy' and gave here a very detailed account of our present knowledge of the radio emission from the Sun. And the book 'Solar Activity' written by Tandberg-Hanssen (1967) has tried 'to give a treatment of all the different manifestations of activity on the Sun in a unique framework: as the inevitable results of the interaction between solar magnetic fields and the solar plasma'. In all these books and most extensively in the last one, readers can find a very complete account of the results obtained in the last decade in the study of solar activity, with extensive lists of references. Papers presented at six symposia, conferences and summer schools organized in 1963 or earlier, were published during the investigated period: The Symposium on Stellar and Solar Magnetic Fields= IAU Symposium No. 22 (Lust 1965), the AAS-NASA Symposium on the Physics of Solar Flares (Hess 1964), the Plasma Space Science Symposium (Chang and Huang 1965), the Summer School 'Introduction to Solar Terrestrial Relations' (Ortner and Maseland 1965), the Utrecht Symposium 'The Solar Spectrum' (de Jager 1965a), and the 1st Consultation on Heliophysics at Tatranska Lomnica (Mergentaler 1964). The following meetings were held during the reported period: The Symposium on Astronomical Observations from Space Vehicles= IAU Symposium No. 23, 17-20 August 1964 (published in Ann. Astrophys. 27 and z8); the Meeting on Sunspots in Florence, 9-12 September, 1964 (Righini 1966); the Meeting on Solar Magnetic Fields and High Resolution Spectroscopy in Rome,

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q.-16 September, 1964 (edited by M. Cimino; not yet published and consequently, some papers presented there could not be included in this Report); the 3rd Consultation on Solar Physics at Tatranska Lomnica, 13-16 October 1964 (Kopecky 1965a); Solar Physics NATO Summer Course at Lagonissi, 12-26 September, 1965 (Xanthakis 1966d); Colloquium on 'The Fine Structure of the Solar Atmosphere', Anacapri, 6-8 June, 1966 (Kiepenheuer 1966b); the InterUnion Symposium on Solar-Terrestrial Physics in Belgrade, 29 August-2 September, 1966 (not yet published); and the 4th Conference on Solar Physics held in Sopot and organized by the Wroclaw Observatory in September 1966 (not yet published). 1.3. Scientific progress report (For details, see sections 2-14). Remarkable progress has been made in our understanding of the general development of active regions. It seems to be clear enough that all solar magnetic fields are basically bipolar units and that the supergranular pattern of the solar atmosphere plays a fundamental role in the development of active regions. The rapidly improving techniques of magnetographic measurements has permitted to resolve relatively homogeneous magnetic fields in complicated multipolar structures and to detect the very fine structure of solar magnetic fields with height in the solar atmosphere. Strong fields in small limited regions in the photosphere as well as isolated chromospheric fields are of particular interest. Chromospheric pictures obtained with the domeless coude refractor at Anacapri (Kiepenheuer 1966b) give an example of the progress achieved in the photographic study of the fine structure of the solar chromosphere. When studying sunspots, one still meets with the most serious difficulty of the stray light, which contributes more than so% in the umbra light. Both the experiments carried out with balloon-home telescopes as well as new methods of theoretical analysis proposed by several authors, have tried to solve this problem. Nevertheless, some of the results of theoretical analyses are still in contradiction, particularly as to the existence or non-existence of subhydrostatic pressures in sunspots. Magnetographic measurements indicate the existence of twisted fields in sunspots. Generally, the variation of the magnetic field strength with distance seems to be similar to that of a dipole submerged beneath the photosphere, at least as the intensity distribution is concerned. Great attention has been paid to the fine structure of the Evershed effect, but the authors did not arrive at a unique solution of the problem. Progress has been made in the difficult transfer problem for lines formed in the magnetic field, where solutions have been obtained for greatly generalized conditions. Attention has been paid to variations of the magnetic field associated with flares as well as to the location of flares with respect to the magnetic field. While our knowledge of the first problem has not significantly improved since the last Draft Report, several authors now agree that flare brightenings are distributed along both sides of a neutral line of the field and usually extend parallel to the neutral line, in their later development. A remarkable progress has been achieved in our knowledge of the characteristic features of proton flares and of the active centres capable of producing proton flares. Successful forecasts of proton flare events during the period of the Proton Flare Project give good evidence of this. The many years' standing problem of the broadening mechanism of Balmer lines in flares has been definitely settled in favour of the Stark effect, at flares projected on the disk. The filamentary structure of flares, first suspected by Suemoto and Hiei, has been proved by several authors. The great interest of solar physicists in flares is well demonstrated by the high number of newly proposed or modified flare theories and many of them have already taken the filamentary structure of flares into account. One has to admire many ingenious ideas contained in these theories but, on the other hand, one cannot escape the feeling that we are still far from being able to understand what the flare phenomenon actually looks like.

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Observations of longitudinal magnetic fields in prominences have progressed in the past three years. They indicate that field strengths in quiescent prominences range from about 2 to 10 G, while active prominences and loops are associated with substantially stronger fields. Great attention has been paid to loop systems which imply a conveyance of field into the corona and are a manifestation of the storage in the corona of fast, non-thermal particles. Another problem which has been extensively studied, is the filament activation by active regions. Newly detected characteristic oscillations of 'winking' filaments, sometimes starting tens of minutes before a flare appearance, might be very significant for our understanding the active processes on the Sun. Analyses of monochromatic solar corona indicate a filamentary structure of coronal condensations, matter in the condensation being largely concentrated in loop systems. A combination of Coronascope II, solar eclipse, and nearly synoptic K-coronameter observations permitted to get a unique series of coronal data covering several solar rotations. In this way, a streamer co-rotating with the chromospheric features could be followed for about two months. June 14, 1966 was the historical date, when on the first time, the Sun was photographed from the surface of the Moon. The role of gyro-resonance absorption and emission by electrons has become better understood, both with regard to the microwave slowly varying component and to the emission of type IV bursts at em and dm wavelengths. Progress has also been achieved towards an understanding of the harmonic structure of type II bursts, an agreed-upon mechanism, however, has not yet been accepted. On the other hand, most of the properties of type I noise storms are still unexplained and the question, how to account for elliptical polarization of type III bursts, is not yet satisfactorily answered. Thanks to the great number of single-frequency records, made by many observatories on a regular scheme, it is now possible to derive spectral diagrams for most of the major radio events. On the other hand, there is still a great want of more data on source positions and polarizations of type IV emission. Direct X-ray spectroheliograms at a variety of wavelengths have verified close correlation of increased X-emission with plage activity; at short wavelengths, beneath'""'"' 15A, the emission arises entirely from centres of activity and seems to be concentrated in small, hot elements embedded in a larger lower temperature region of the coronal condensation. The degree of concentration to active regions as observed by slitless spectra in the XUV wavelengths, also depends markedly on the ionization equilibrium temperature of the emitting ion and seems to be a function of the stage of development of the spot group. It has been agreed that the X-ray emission from active regions as well as many X-ray enhancements associated with flares are of thermal origin. Contradictory conclusions appear, however, as to the height of these emissions in the solar corona, as well as to the mechanism producing possibly non-thermal X-ray bursts. The observation of the solar eclipse in 1966 by means of the Explorer 30 satellite by the Arcetri group has demonstrated the wide applicability of the RTT monitoring system. The number of papers dealing with observations of solar particles from space vehicles has increased many-fold since the last report. Very important studies were made with the Pioneer 6 space probe; the data indicate the existence of large numbers of filamentary tubes, originating at the Sun but intertwined in interplanetary space. In spite of twisting and intertwining of these filaments, the spiral configuration remains. Cosmic rays are envisioned as constrained to the flux tubes. A number of proton increases was observed aboard several space probes, only partly associated with flares. Some events were even recorded aboard two or more Soviet or American space probes and deep-space satellites. The important role of ex-particles in streams of high-energy particles, recognized during the past years, throws some doubt on the terminology of the 'proton' flare events. Nuclei with Z > 3 have been observed after major flares on at least four occasions and possibly in some other events, as well. It is not yet clear, however, to what extent the composition of the nuclei reflects the photospheric abundance.

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Evidence for solar-flare electrons was also obtained from IMP and Electron satellites and from the Mariner 4 space probe. A comparison of IMP-I magnetic field data with solar magnetograph observations has shown that the interplanetary magnetic field is directly tied to and co-rotates with the solar photospheric magnetic fields. During the minimum period of solar activity, since I962, the interplanetary magnetic field was divided into 2, and since late I963, into 4 sectors, alternating in direction toward and away from the Sun, and this structure had correspondence to grossly ,averaged magnetic features in the photosphere. This low-activity structure of the interplanetary space becomes less stable as the solar activity increases. Summarizing these discoveries, one observes that, generally, two basic features characterize the past period in the research of solar activity: a progressive tendency to discover fine structure in all the studied phenomena and a gradual transformation of our old conception of the interplanetary space into the new one of an extensive and expanding solar atmosphere, directly studied with deep space probes. 2. EQUIPMENT AND METHODS 2. 1.

Optical observations

A new solar research station of the Cambridge Observatory was completed at Rabat (Malta). It is equipped with a large horizontal solar telescope of about 40 meter length with a large Babcock grating and all facilities for photographic, photometric and magnetographic work. At the Observatory of the University of Hawaii four new solar instruments have been installed: A Io-inch aperture (25 em) Lyot coronagraph which feeds a coude spectrograph with dispersion I or 6Afmm; a dual coronagraph which is to obtain simultaneously photographs through 2A interference filters of the corona in the green line and of active prominences in Hex; a moderately large-scale Hex camera which is used to study individual active regions under conditions of good seeing; and a photographic polarimeter for determining Stokes parameters of the radiation in broad spectral bands. The Manned Spacecraft Center installed in I966 three Hex solar telescopes employing a Lyot-Ohman filter, one on a seventy foot tower at Houston (Texas) and the other two in Carnarvon (Australia) and in the Canary Islands. New solar observatory of the Deutsche Forschungsgemeinschaft near Locarno, equipped for observations of active solar phenomena, was described by Bruckner (1964). The new domeless coude refractor for solar work on Capri was described by Kiepenheuer ( 1964b). Inner tube contains a 35 em objective of I 5 m focal length and an outer tube protects this first one against wind and rain. Through the polar axis the solar light is guided to a spectrograph. A new solar telescope and spectrograph with 70 em coelostat and 50 em objective was also installed at the Kwasan Observatory (Nakai and Kubota 1964). The McMath solar telescope at Kitt Peak was described by Pierce (r964), and the description of an evacuated tower telescope planned for Sacramento Peak Observatory was given by Dunn (r964). A triple heliograph, which allows to take simultaneously Hex and K line filtergrams together with a photospheric picture was installed at the National Observatory in Athens. At this Observatory also a new automatic solar telescope equipped with Halle Hex filter and TV technique was built. At the Monte Mario Observatory in Rome, regular patrol service has been started in I964-65 both in the Hex and K lines. A new Halle Hex filter at Irkutsk allows to get automatically Hex filtergrams at o, ± 0·25, and ± o·soA from the line centre (Skomorovsky I966). The composite filtergrams taken in three wavelengths (o and ± o·soA) in the Hex line at Lockheed were described by Larmore and Ramsey (I964). New equipment, which allow to photograph simultaneously solar disk and solar limb, were described by Michard (1965) and by Carroll (I965). A new space-velocity coronagraph, which allows to get simultaneous photographs of the prominence image and of the Hex line in its spectrum was installed

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at Ondrejov (Valnicek and Kleczek 1964, Valnicek et al. 1965). The new spectroheliograph of the Catania Observatory, applicable to Hoc, HS, K and >t4247lines was described by Fracastoro and Cristaldi (1964). A new electrophotometer for fast recording of the Hoc line profiles of limb phenomena was built at the Kiev Observatory of the Academy of Sciences (Gurtovenko and Skorik 1965). A new Zeiss (Jena) coronagraph was installed at Lomnicky Stit in High Tatra Mountains (Lexa 1963). The new coronagraph and spectrograph at Climax was described by Rush and Schnable (1964). Modifications of the Lyot coronagraph, leading to an increase of speed of measurement of the absolute intensities of coronal lines in various coronal regions have been realized at Pic-du-Midi (Demarcq et al. I965). The Astrophysical Observatory Arosa has been equipped in I965 with a new Zeiss (Oberkochen) coronagraph. It is combined with a powerful grating spectrograph; using a dispersion of 5A/mm and a slit width of o·o3 mm, the exposure time for the >t5303 line is one second only. The K-coronameter of the Norikura Corona Station and the method of observation and reduction of the observed results were described by Nagasawa et al. (I965). A description of the optical scheme and the main characteristics of a large Lyot-type coronagraph which is being made in U.S.S.R., was given by Nikolsky and Sazanov (I966). A combined narrow-band filter consisting of 3 A multilayer filter and the three thickest elements of Lyot-bhman filter was described by Zirin ( I966). Ramsay ( I966) gave a description of a new monochromatic filter based on a series of plane-parallel Fabry-Perot interferometers aligned in a parallel mode. Lyot-bhman and Sole filters produced in Czechoslovakia were described by Valnicek {I965a). Hamana and Suzuki (I966) studied a method of reducing the effect of finite filter pass-band on the intensity measurements of flares. A double image line shifter proposed by bhman (I966a) has been used by Nilsson (1966) for the purpose of determining Doppler velocities of dark and bright surges. bhman (I 966b) also made a suggestion for reducing scattered light in sunspot photometry by a special system of two diaphragms and tests have shown that the influence of diffracted light from the circumference of the objective is reduced to a minimum with this device (Kussovsky 1966). bhman (1966c) also proposed other methods for the same purpose. An electronic device for discriminative measurements of sunspot areas was described by Boev et al. (1965). Giovanelli (1966b) discussed methods and techniques for the observation of sunspots in white light, including discussions of seeing, scattered light, thermal deformation of mirrors and photographic techniques. 2.2. Magnetic field measurement Since the beginning of I 964 considerable effort has gone into the construction of new instrumentation at the I50-foot solar tower telescope at Mt Wilson. A guider and scanning system have been installed which now enable to scan the solar image very accurately in any desired raster pattern. The solar magnetograph has been completely rebuilt, and two spectrum lines can now be used simultaneously. Data are recorded on a magnetic tape recorder for later analysis with a digital computer (Howard 1966). A double magnetograph recording simultaneously magnetic field in two different lines (>t5250 and >t6103, or Hoc) also started to work in 1965 at the Crimean Observatory (Severny 1966a) and a similar device has also been developed at Nizmir (Moscow), for simultaneous observations in A5250 and H~ lines (Zhulin and Mogilevsky 1965b, Mogilevsky et al. 1965). An earlier description of the electronic scheme of the Crimean magnetograph was published by Nikulin (1964) and further details concerning the magnetograph at Nizmir were described by Iospha and Mogilevsky (1965) and by Ioshpa and Obridko (1965d). A new magnetograph recording all components of the solar magnetic field has been designed at Irkutsk (Kuznetsov et al. 1966). The domeless coude refractor at the German station at

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Capri (Kiepenheuer 1964b) is combined with a longitudinal and transverse magnetograph with automatic mapping of the field distribution (Deubner 1966). The McMath-Hulbert Observatory has improved its measurements of solar magnetic fields through the addition of a Glan Thompson prism and mica quarter-wave-plate to the optical train of the vacuum spectrograph. A magnetometer for the study of weak longitudinal magnetic fields has been developed by Bhattacharyya at Kodaikanal. A Babcock-type magnetograph has been established in the solar tower on Monte Mario in Rome. At this Observatory also the measurement of sunspot magnetic fields has been modernized and is now carried out by means of a photomultiplier and a study of the Zeeman effect by atomic beam without using high dispersing spectrographs is in progress. A detailed summary of methods of measurements of solar magnetic fields was presented by Severny (1966c). Bruns et al. (1965) described a method used at Crimea for measurements of transverse magnetic field. The method of observation of the total vector magnetic field with the Pulkovo Observatory magnetograph was described by Kotljar (1964). The method of simultaneous measurements of solar magnetic fields on two levels in the solar atmosphere was explained by Zhulin ( 1965) and the selection of proper lines for this purpose was discussed by Dubov (1966a) and Severny (1966a). Kuklin (1966b) described the electro-optical modulator of the solar magnetograph at Irkutsk. The degree of reliability of radial velocities obtained by means of a magnetograph was discussed by Ioshpa and Obridko (1965b) and by Ikhsanov (1966) and the influence of seeing on measurements of radial velocities with a magnetograph was investigated by Gopasyuk and Severny (1964). A method for deriving the complete magnetic field from magnetographic measurements of the longitudinal Zeeman effect was proposed by Schmidt (1964, 1965) and modified by Semel (1967). Possible effects of steep field gradients between close spots on results obtained with a scanning magnetograph were discussed by Teske et al. (1964). The method of magnetic field measurements at Meudon has been analysed by Semel (1967). A method of measuring solar magnetic fields by using a birefringent filter with twin transmission bands was proposed by Ohman (1965) and a very similar method actually has been applied in Meudon. A method of the determination of three components of the magnetic field of sunspots by means of a 'lambdameter' was described by Rayrole (1964). The same author (Rayrole 1966) has designed and proven a method for deriving the full magnetic field vector from photographic measurements of the Zeeman displacements of lines observed in various polarization states. The method uses simultaneously two lines from the same multiplet but with different Zeeman patterns, which gives the possibility to determine also the scattered light in spots. The magnetograph of the High Altitude Observatory at Climax, used for measurements of magnetic fields in prominences using the Hoc line was described by Lee et al. (1965). Sensitivity of the equipment equals two gauss. Smolkov ( 1966a) has shown that, in principle, it is possible to get information on the coronal magnetic field when applying a sensitive photoelectric method to the .\5303 line. 2.3. Solar radio astronomy New radiotelescopes have been installed at several observatories: 8 mm wavelength at the Crimean Observatory (Efanov and Moiseyev 1965), 2700 MHz at the Dominion Radio Astronomical Observatory in Penticton (Covington and Locke 1965), 2000 MHz at New Delhi (Sarma and Joshi 1965), 930 MHz at Bordeaux (Bernyer et al. 1966), 700 MHz at Fleurs, 408 MHz at Nan 20 keV) X-ray events were connected to flares of the explosive type. The extraordinary enhancements of X-ray emission associated with the flares of 6 and 7 August 1960, were explained by Svestka (1964b), on the basis of flare spectra, as due to an increased density in the active region in which the flares appeared. Chubb et al. (1966) presented an improved analysis of X-ray measurements in the hv > 20 keV region, carried out from rockets during three class 2+ flares in 1959. Two of these flares showed spectra equivalent to that expected from a thermal plasma with Te ~ 108 °K. Other events can be explained by thermal radiation, too, if the balloon measurements are properly corrected. The authors stress that there currently exists no definitive observational evidence for non-thermal X-ray emission. SID effects were used to a study of solar X-ray bursts by several authors: Fortini (1963) has found similar trend of SEA and SCNA events if produced by flares recurring in the same area of an active region and she ascribes it to the influence of persistent magnetic fields that control the particle motion; a thermal model does not seem capable of explaining these recurrent characteristics. On the basis of ionospheric measurements, Odincova (1964) has made an estimate of the intensity distribution below 1oooA in the spectrum of the flare of 28 August 1958. SEA data were analysed by Erushev (1965) who estimated that the maximum energy X-ray flux below 2A varied within 10-7 to 10_ 3 erg cm- 2 s-1 in various flares. Neshpor (1965) deduced a time variation of the X-ray spectrum during the flare of 23 November 1957, from SID records. Eliseyeva (1966) has confirmed that X-ray flares do not correspond to type III bursts. On the basis of an analysis of simultaneous observations of X-ray emission of the Fe xv

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and Fe XVI lines and 10·7 em radio emission, Shklovsky (1964) has shown that a coronal temperature of,...._, 1·5 x 106 °K is sufficient to explain the X-ray emission on the quiet Sun. The X-ray emission of flares is explained by the inverse Compton effect on relativistic electrons with energies ,...._, 107 to 108 eV. Zheleznyakov (1965a), too, presented the same explanation. On the other hand, Acton (1965a) concludes that the X-ray emission of flares cannot be explained by the inverse Compton effect and shows that the solar flare radiation can be explained by thermal processes if Te = 4 - 5 x 106 °K (Acton 1965b). Acton (1965c) also suggested that X-rays in flares might be produced by electron transitions among inner K-, L-, and M- spheres, in consequence of an ionization by energetic electrons. Korchak (1965b) concludes that the X-ray emission is due to bremsstrahlung of non-relativistic and subrelativistic electrons. The X-ray burst accompanying the flare of 28 September 1961, could be explained by Korchak (1965a) by bremsstrahlung if the particle density in the breaking levels was two orders higher than in the undisturbed atmosphere. If the electron energy spectrum is extrapolated to relativistic energies, the observed centimeter burst can be explained as well. Elwert (1964), too, tried to combine X-ray, radio and particle observations of a flare in one homogeneous system. According to the later Korchak's (1965b) paper, however, it seems unlikely that a single mechanism will provide a smooth fit from X-rays to radio bursts. Possible mechanisms of y-ray production in solar flares were discussed by Dolan ( 1964) and by Dolan and Fazio (1965). Until now, however, all trials to detect y-rays from the Sun, have given negative results (Fazio 1964, Kraushaar et al. 1965, Frye and Reines 1966). 12. HIGH ENERGY PARTICLES

A detailed general summary on solar proton events was presented in the NASA Solar Proton Manual edited by McDonald (1963). Review papers on high-density particles emitted from the Sun were published by Obayashi (1964a, b), K. A. Anderson (1964b), Roederer (1964a, b), de Jager (1965e) and Ogilvie (1965). A very illustrative critical review paper on particle and radio emission from the Sun was presented by Schatzman (1965b). Malitson and Webber (1963) and Webber (1964) described general characteristics of solar cosmic ray events and Fichtel et al. (1963) summarized details of individual solar particle events. Lists of PCA events were given by Bailey (1964), Basler and Owren (1964), Cummings (1965), FritzovaSvestkova and Svestka (1966a) and, for the period before 1956, by Svestka (1966d). Solar proton events during the IQSY period were summarized by Goedecke et al. (1967). Kfivsky (1965c, 1966) studied the flight time of solar protons to the Earth and discussed a space model of the clouds of high-energy protons ejected from flares (1965b). Van Allen et al. (1964), Hakura (1965), Leinbach et al. (1965), Chivers and Burrows (1966), and Adams and Masley (1966) investigated relations of PCA records to the energy spectrum of highenergy particles and the progressive softening of the spectrum during the PCA development. Yoshida and Akasofu (1965) have shown that solar flares associated with cosmic-ray increases are the most energetic throughout the entire range of the energy spectrum of solar particles. Shea and Smart (1965) proposed an analytical method to analyse flare-associated cosmic ray increases, effectively including as many stations as possible. Statistical comparison of flares and flare-associated phenomena with ground-base measurements of cosmic rays were made by Vladimirsky and Pankratov (1964), Dorman et al. (1964), Yoshida (1965) and Vladimirsky et al. (1966). In the last two papers, a definite statistical increase of solar cosmic rays (,...._, o·5%) has been found for meter type IV bursts and X-ray flares. Cosmic-ray increases not associated with solar flares have been suspected by Dorman et al. (1965). Chirkov et al. (1965) and Kuzmin et al. (1965) studied cosmic-ray variations associated with active regions passing over the solar disk in December 1957 and in July 1961, respectively. Vladimirsky (1965a) expressed an idea that all solar flares produce low-energy cosmic rays.

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The number of papers dealing with observations of high-energy particles from space vehicles has increased many-fold since the last report. In this section we discuss mostly the flare-associated events; for other observations see section 13. K. A. Anderson (1964a) re-examined the solar proton flare events of late August 1957. Arnoldy et al. (1964) made a comparison of the cosmic radiation measurements from the Earth, balloon ion chambers and Pioneer-s during the March-April 1960 events. Four solar proton events observed by Explorers XII and XIV were discussed by Bryant et al. (1964, 1965a). They have found that the rate of propagation of protons is linearly related to particle velocity, such that the time to reach maximum intensity is inversely proportional to velocity and conclude that the propagation involves a degree of scattering that is independent of the energy. Charakhchan A. N. and T.V. (1965a) have shown that the differential energy spectrum of solar flare particles has the same exponent(""' 3) in the several hundred MeV range for various flares. In the higher energy range the spectrum exhibits a discontinuity and the exponent increases to s-6. The location of the discontinuity is different in different flares. Softening also occurs after the onset of a magnetic storm (Vakulov et al. 1964, Charakhchan A. N. and T. V. 1965b). Spectra of high-energy solar protons were also studied by Ogilvie and Bryant (1964), Bennett (1964), Dorman and Miroshnichenko (1965, 1966), Laxutin (1965), Paulikas et al. (1966) and Charakhchan et al. (1966). The last authors found an indication that the diffusion coefficient of solar protons in the interplanetary space increased at about three-times from 1960 to 1963. Increases of lower-energy(""' I MeV) protons were recorded with several space probes and analysed by Krimigis and Van Allen (1966) and by Vernov et al. (1966a, b). Only some of these increases can be directly associated with solar flares. The anisotropy of solar cosmic rays was studied by McCracken (1963) and by Kuzmin et al. (1965), but the most important anisotropy studies were made with the Pioneer 6 space probe, particularly at the proton event of 30 December 1965 (Fan et al. 1966, Bartley et al. 1966, McCracken and Ness 1966). It has been found that the cosmic ray anisotropy is well aligned with the interplanetary magnetic field and the direction of anisotropy is shown to exhibit marked and abrupt changes, well correlated with the changes in the direction of the magnetic field. The data from Pioneer 6 indicate the existence of large numbers of filamentary tubes, originating at the Sun but intertwined in interplanetary space. Cosmic rays are envisioned as constrained to the flux tubes. The important role of a-particles in producing PCA's was shown by Weir and Brown (1964), and by Hakura (1965). The high-altitude balloon measurements of the relativistic solar a-particles in the late phase of the 12-13 November 1960 event were discussed by Yates (1964), who found a power law instead of the exponential rigidity spectrum. This result was criticized by Waddington and Freier (1965). The increased participation of a-particles after the onset of a sc geomagnetic storm was discussed by Sakurai (1965d). Review papers on the composition of solar cosmic rays were presented by Fichtel (1964) and by Biswas and Fichtel (1965). Reviews of the results obtained from the study of cosmic rays with Soviet satellites and space probes, with a particular emphasis to the detection of nuclei heavier than protons were given by Ginzburg et al. (1963, 1964). The participation of heavy nuclei in solar cosmic rays was also discussed by Vladimirsky (1964). Cosmic-ray nuclei with Z > 2 have been observed after major flares on at least four occasions (Biswas et al. 1963, 1966, Biswas and Fichtel 1964). During the 18 July 1961 event the increase in the flux of medium nuclei (6 ~ Z ~ 9) was a factor 40 over the normal cosmic ray flux. Biswas and Fichtel (1964, 1965) concluded that the composition of the nuclei appeared to reflect the photospheric abundances. Quite an opposite conclusion, however, was made by Charakhchan A. N. and T. N. (1965). Increases of the flux of nuclei with Z ;:;::. 5 and Z ;:;::. 15 were also recorded aboard the Electron-2 satellite (Bloch et al. 1965, Kurnosova et al. 1966) and with the second Soviet cosmic rocket (Vladimirsky 1965b). Most of these increases,

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however, do not seem to be connected with solar flares and Vladimirsky suspects that one might meet there with a new effect associated with some solar events different from the flare phenomenon. Solar neutrons may have been detected by means of balloon observations after an importance 3 flare. A flux of 148 ± 6o neutrons m- 2 s-1 in the 2o-16o MeV range was determined (Krishna Apparao et al. 1966). On the other hand, Vela satellites operating since October 1963 have not detected any neutron bursts in excess of 1·5 x 10 3 neutronsjcm 2 integrated intensity even after importance 3 flares accompanied by type IV radio bursts (Blame and Asbridge 1966). Lingenfelter et al. (1965) calculated the intensity and energy spectrum of neutrons above 1 MeV produced by flare-accelerated protons and a-particles in the photosphere. They have found that bursts of solar neutrons following major flares should be observable at high altitudes. Roelof (1966) has shown that due to diffusion, neutron-decay protons are insensitive indicators of the presence of neutrons in solar flares and it is unlikely that neutrons from a flare can be detected by means of proton observations. Evidence for solar-flare electrons was obtained from the IMP satellites (Cline et al. 1964, Cline 1966, K. A. Anderson and Lin 1966), Electron-2 satellite (Tindo 1965) and Mariner 4 space probe (Van Allen and Krimigis 1965). While the solar origin of the electron flux reported by Cline et al. is doubtful, the other authors found direct relations of the recorded bursts of electrons to bursts of radio noise and X-rays associated with flares. The western longitudes of all the flares suggest a restriction of the electrons to field lines with a half angle of 15-20°. The acceleration of protons by hydromagnetic shocks induced in the corona by heating due to flares was analysed by Weddell (1965). Solution of the relativistic equations of motion of protons subject to the moving magnetic field accompanying a shock leads to results, which agree in several aspects with the observed characteristics of solar proton events, nevertheless the resulting proton flux seems to be much too small. Wentzel (1965) and Sakurai (1965d) consider the Fermi acceleration mechanism as the predominating process in accelerating solar cosmic rays from flares. Korff (1964) has concluded that the acceleration must take place at levels of about 100 ooo km above the photosphere. The initial phase of a solar proton event was investigated by G. C. Reid (1964) and an attempt was made to treat the diffusion through the solar atmosphere in a quantitative fashion. The possibility of a storage of energetic particles in the corona was discussed by Malville (1964). Willis (1966) examined the motion of an isolated energetic charged particle in a force-free magnetic field with rectilinear lines of force. He has found that under certain conditions a particle travels predominantly across the magnetic lines of force and it is suggested that some energetic charged particles may be able to escape from force-free magnetic fields by this process. The propagation and diffusion of solar flare protons and the modulation of the energy spectrum in the interplanetary space were discussed by Parker (1964d), Ivanov and Kolomeets (1965), Fibich and Abraham (1965) and Shishov (1966). Krimigis (1965) suggested a unified interplanetary diffusion model and used it for an interpretation of the time history of the intensity of several cosmic ray events. Wibberenz (1966) pointed out the significance of drift motions for solar energetic particle propagation in interplanetary space. I

3.

SOLAR WIND DISTURBANCES

Review papers on solar corpuscular radiation including enhanced solar corpuscular emission were written by Krimigis (1963), Parker (1964b), Mustel (1964a, b, c) and by Colburn and Sonett (1966). Scientific findings of Mariner 2 were reviewed by Sonett (1963), and by Snyder and Neugebauer (1964, 1965). Some papers concerning solar wind disturbances also appeared in 'The Solar Wind' symposium edited by Mockin and Neugebauer (1966). Parker (1966) summarized his earlier ideas in a synthetic picture: Disturbed conditions in the interplanetary space result when there is more turbulence in the wind than usual and/or when there is a

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sudden increase of coronal temperature in association with a solar flare. The 27-day recurring disturbances are associated with narrow regions of turbulence between broad regions of wind. Sudden heating of the corona at the time of a solar flare results in a sudden increase in the rate of expansion of the corona giving a blast wave which propagates outward through the wind. Nevertheless, some authors still prefer the magnetic bottle model in its original Golds form, which has some advantage in explaining the flare-associated corpuscular emission in an illustrative way. Some common features of the Parker's and Gold's models were discussed by Santarelli ( I965). Using measurements aboard Mariner 2, Vela 2, IMP I and Explorer I4, new determinations of solar wind velocity and temperature were made by Wolfe and Silva (I965), Wolfe et al. (I966), Neugebauer and Snyder (I966) and Strong et al. (I966). From quiet to disturbed conditions, proton's velocity increases from slightly more than 300 km s-1 up to Boo km s-1, temperature from the order of Io4 °K up to 9 x Io5 °K and proton density from ,...., 5 to 8ofcm 3• The maximum density usually appears at the leading (western) edge of each stream. The magnetic field temporarily increases well above IO gamma in association with disturbances from the Sun (Ness et al. I966a). The interplanetary magnetic field is directly tied to and co-rotates with the solar photospheric magnetic fields. This has been shown dramatically from a comparison of IMP-I magnetic field data with solar magnetograph observations. The magnetic lines of force extend in Archimedes spirals in accordance with Parker's theory of the solar wind. During the threemonth interval of IMP-I observations {I963 November 27 to I964 February I7) the interplanetary field divided into 4 sectors, alternating in direction toward and away from the Sun. These sectors had correspondence to grossly averaged magnetic features in the photosphere (Ness and Wilcox I964, Wilcox and Ness I965, Ness I966b, Ness and Wilcox I966a, Smolkov I966b, Sakurai I966b, Ness et al. I966b). Co-rotation of the systems of corpuscular streams also appears from the stability of the 27-day recurrence of geomagnetic disturbances (Vsechsvyatsky I964, Lapointe I964), cosmic ray intensity (Mori et al. I964, Balasubrahmanyan et al. I965), and proton increases (Gregory and Newdick I964, Bryant et al. I965b), and it has also been supported by measurements of Pioneer 6 and IMP-3 (Ness I966a). Davis {I964, I965, I966), Davis et al. {I964, I966), Coleman et al. {I966), Lazarus et al. {I966) and E. J. Smith et al. {I966) discussed observations made aboard Mariner 2 and 4, IMP-I and OGO-I. It appears that the polarity pattern of the interplanetary field changed considerably between August I962, where two reversals occurred per solar rotation, and November I963, when the number of reversals was doubled. In late I964, the Mariner 4 magnetometer recorded a 4-sector polarity pattern similar to that observed with IMP-1. Starting early in I965, however, the Mariner-4 data show a considerable evolution of the patterns, which become less definite than they were earlier. This suggests that the pattern becomes less stable as the Sun becomes more active. However, at least one feature of the patterns may have persisted for the whole period of more than two years. Some observations of recurrent proton increases suggest a trapping of protons over certain regions (Bryant et al. I963, I965, McDonald and Desai I966). Interplanetary magnetic fields co-rotating with the Sun apparently confine the protons from flares and 27-day recurring regions to given sectors and thus influence the appearance or non-appearance of protons at the Earth (O'Gallagher and Simpson I966). Helium of solar origin in these recurrent particle streams was detected by Gloeckler {I965). Snyder et al. {I963) have concluded that M-regions are the emitters of high-velocity plasma and Snyder {I964) tried to associate the solar wind velocity variations observed by Mariner 2 with observed plages on the Sun. Mustel {I965b) examined the two theories of the formation of quasistationary corpuscular streams from the Sun: (I) the streams originate in active regions, and (2) particles generated in undisturbed regions are deflected by neighbouring active regions. According to Mustel, all geomagnetic, satellite and space probe data confirm

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the first hypothesis. Nevertheless, many other authors consider the second alternative, i.e. the hypothesis of 'cone of avoidance' as the more favourable one, particularly Allen (I964), Saito (I964), Sinno (I964) and Nojima et al. (I964). The outflow of particles from M-regions was discussed by Piddington (I964) and Mustel (I966) and the structure that would be expected to develop when a fast stream in the solar wind is embedded in a slower ambient wind was considered by Hirshberg (I965). McCracken et al. (I967) report the observation, made with Pioneer 6, of a number of recurrent phenomena having all the characteristics of Forbush decreases apart from any flare-association. They were, however, ultimately correlated with recurrent M-regions. The north-south asymmetry in the solar wind as observed with IMP-I and 3 was discussed by Ness and Wilcox (I966b). Krivsky and Letfus (I965) suppose that this asymmetry is due to an inclined interplanetary magnetic field caused by the galactic wind. The existence of a solar proton belt in a distance of I·5-2 A.U. has been suggested by Vernov et al. (I966c) on the basis of proton flux measurements carried out aboard Zond 3 and Venus 2 space probes. By comparing PCA events and Forbush-type decreases, Gosling (I964) proved a storage of high-energy protons in the cloud ejected from a flare and Haurwitz et al. (I966) and Svestka (I966e, I967) deduced an asymmetrical magnetic field distribution in the cloud, with a magnetically strong western boundary. Geometrical dimensions and kinematic characteristics of solar corpuscular streams have been estimated by Mustel and Maisuradze (I966). A possibility of connection of two magnetic bottles in the interplanetary space was pointed out by Gopasyuk and Krivsky (I967). From the interaction point plasma moves towards the Sun, as has actually been observed in some cases by Vitkevitch and Vlasov (I966) from the radio sources scintillation. A 'cleaning' of the interplanetary space by solar particle emissions was discussed by Lebeau et al. (I964) for the case of flares of 3 July I957· The influence of the interplanetary magnetic fields on the propagation of solar protons was examined by Sakurai (I 96 5c ). Production of pairs of shock waves by the flare-associated enhanced solar wind was suggested by Sonett and Colburn (I965) and discussed by Sturrock and Spreiter (1965) and by M. Simon and Axford (I966). A scheme of permanent generation in active regions of corpuscular streams consisting of discrete plasmoids with own quasi force-free magnetic field has been offered by Mogilevsky (1964, 1965, 1966, Kalinin and Mogilevsky 1965). His analysis of the observations of magnetic fields in the interplanetary space confirms that the corpuscular streams with own magnetic field have a discrete structure. Akasofu {I964) has tried to show that the solar plasma ejected from an active region can contain an appreciable amount of neutral hydrogen atoms. This supposition has been criticized both from the solar and geophysical points of view by Brandt and Bunten {I966) and by Cloutier {I966). Cloutier shows that the flux of neutral hydrogen is less than 10-5 of the total solar wind flux at I A.U. 14.

SOLAR-TERRESTRIAL RELATIONS

Quite a lot of papers relating to the problems of solar-terrestrial physics, have already been mentioned in the preceding sections. Particularly, reader's attention is called to sections 7.3, 12, and 13. Jonah et al. (I965) have prepared a five-volume catalogue which brings together the major optical, radio frequency, ionospheric and geomagnetic phenomena and events for the I9th solar cycle. Pick ( I966) summarized the main optical and radioelectric properties of flares associated with SID, PCA and sse magnetic storms. A synthetic study of severe solar-terrestrial disturbances of 9-12 February 1958, was presented by Hakura and Nagai (1964) and the same events were also described by Rivera and Gonzales (I964). Connections between the fine structure of type IV bursts and the production of PCA'S

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with long and short delay times were investigated by Bohme (1g66). Bell (1963) has pointed out that type IV bursts which cover the full frequency range from microwaves to meter wavelength are strikingly more successful in the production of PCA events (as well as geomagnetic storms) than are type IV bursts limited to two or three octaves of the spectrum. Fritzova-Svestkova and Svestka (1g66a) investigated in detail the association between type IV burst flares and PCA events. They have concluded that strong PCA's are caused predominantly by flares between I0° E and 90° W on the solar disk and give the probability of PCA production by type IV burst flares as a function of the flare position on the disk. There seems, however, to be a general tendency of some active regions to emit or not to emit high-energy protons from type IV burst flares to the Earth. Statistical association of flares with Forbush decreases during two solar cycles was studied by Krymsky and Shafer (1965). The series of Forbush effects of September 1963 was studied by Fischer and Kfivsky (1965). A close correlation between the integral flux of high-energy solar protons and the amplitude of the associated Forbush-type decrease has been found by Pankratov ( 1965). Associations between flares, type IV bursts, and geomagnetic disturbances were studied by Akinjan and Dolginova (1965). Bohme (1964b) has found that intense type IV bursts produce, on the average, more intense geomagnetic storms and the corresponding delay time is shorter. Sudden commencement magnetic storms recorded at Zo-se during 1936 to 1962 were studied in association with solar flares and type IV bursts by Fan Chen (1965). Fritzova-Svestkova and Hfebik (1964) have confirmed that there exist very important flares without any magnetic storm and major storms without any flare. They have also confirmed, however, that all flares associated with type IV bursts are sources of corpuscular streams. Fritzova-Svestkova (1965) also studied the delay times of major and weak storms. Caroubalos ( 1964) established a statistical relationship between the delay time of geomagnetic storms and the radio energy emitted by the associated type IV burst. Mustel and Egorova (1964, 1965) and Mustel (1965a) have shown that the recurrent geomagnetic disturbances are connected with the passage of active regions through the central solar meridian. Geoactive chromospheric flares are uniformly distributed over the solar disk, but the energy of the geomagnetic disturbance decreases with the increasing distance of the flare from the central meridian. According to Bell (1963), So% of the major storms arise from flares located within 20° of the central meridian. Fritzova-Svestkova (1966) deduced from the longitude distribution of flares producing major geomagnetic storms some conclusions on the density distribution and the trail curvature of the corpuscular streams ejected from flares. Billings and Roberts (1964) discussed the origin and some properties of the 27-day variations of geomagnetic activity from the point of view of Parker's model of the solar wind. The close correlation of central-meridian passages of unipolar magnetic regions with recurrent geomagnetic storms during the last solar minimum was discussed by Bumba and Howard (1g66b). Ballario (1966) has examined the solar and geomagnetic activity during the IQSY Retrospective World Intervals for 1964 and 1965. She concludes that the observed KP maxima are correlated with central meridian passages of regions in which plages, mostly associated with spot groups, show remarkable development changes. Siastna (1964) and Bateman and Oster (1965) verified the earlier Becker's result: If two sunspot groups are located at the same longitude but on the opposite hemispheres, their passage through the central meridian causes a decrease of the KP index within approximately two days. If, however, the longitude difference increases to about I0°, the AP index strongly increases. Stastna suggests that this is connected in some way with the fact that in the first case opposite polarities, while in the second case identical polarities are located at the same longitude. Halenka (1967) makes an attempt to explain yearly variations of geomagnetic activity by an existence of two opposite active intervals of heliographic latitudes on the Sun.

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Bednafova-Novakova (r964) and Halenka (1964) have tried to show that flares are not sources but only indicators of some events of the ejections of corpuscular streams from the Sun. They believe that the actual source of the corpuscular emission are filaments and the most geoactive phenomena on the Sun are filaments associated with unstable sunspot groups (Bednafova-Novakova 1964a, 1966a, Bednafova-Novakova et al. 1964, Halenka r966b). Halenka (r966a) even tries to prove that geomagnetic storms erroneously ascribed to proton flares were caused, in fact, by central meridian passage of unstable filaments and BednarovaNovakova (r967) opposes the opinion that sudden disappearance of filaments is caused by flares. Bednafova-Novakova (r966b) and Bednarova-Novakova et al. (r964) have also pointed out that when forecasting geomagnetic activity it is necessary to know the coronal formation extending over the solar central meridian at the given moment. This is in agreement with the conclusion made by Gnevyshev and 01 (r965) that the mean annual values of geomagnetic disturbances are connected with the intensity of the ,.\ 5303 A coronal line more closely than with any other index of solar activity. I

5.

ADMINISTRATIVE REPORT

Two working groups of Commission ro were active during the reported period: (a) The working group on CSSAR was established at the Hamburg meeting in 1964, in the following composition: Michard (chairman), Dodson-Prince, Fokker, Giovanelli, Jefferies, Kiepenheuer, Righini, Roberts, Rosch, Sevemy, H. J. Smith, Svestka, Waldmeier. (b) The working group on coronal intensity standardization was established in 1966 sponsored both by the IAU Commissions ro and 12, in the following composition: Rosch (chairman), Gnevyshev (secretary), Nagasawa, Newkirk, Waldmeier. In fact, this is a re-establishment of an earlier Working Committee, which treated some problems of coronal observations in the period 1958-61. Many observers of the solar corona have been of the opinion that some more work on the standardization of coronal data is urgently needed. This working group has planned to hold a meeting at Bagneres-de-Bigorre before the Prague General Assembly, in August 1967. Since important parts of the activity of these working groups are envisaged for 1967, i.e. after submitting the present Report for press, we have preferred not to include any partial reports here, and the chairmen of both these working groups will present verbal reports at the meetings of the Commission 10 in Prague. The following recommendations are to be considered: (r) A. H. Shapley recommends to discuss, from the point of view of Commission ro, the proposal to establish a solar-terrestrial service and its proposed status. This proposal is based on a resolution taken at the URSI XV Assembly, Munich 1966, calling on IUCSTP to make the study and potentially arrange for the establishment of such a service. Commission ro could recommend for or against the establishment of such a service and make comments on its needs and terms of reference. (2) A. H. Shapley recommends to discuss the experience with the new IAU classification of flare importances and to have a discussion whether other international standards may be needed as regards description of other forms of solar activity in addition to Ha flares. The possible need for such additional work on standardization of descriptions could benefit from a general discussion at Prague and eventually lead to establishment of an appropriate working group if there appears a need for it. (3) A. H. Shapley would also be interested in having a discussion on the success of the IQSY solar activity forecasts and also whether the post-IQSY forecasts made and distributed

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by IUWDS and potentially modified to serve non-solar-minimum conditions are useful or expressed in terms appropriate to the present understanding of the development of solar activity. (4) A. D. Fokker recommends to devote a discussion to the Quarterly Bulletin on Solar Activity, with a particular emphasize on Resolution 3 of the last Hamburg meeting. This resolution concerns the possibility of contributing solar magnetograms to the Quarterly Bulletin. (5) W. 0. Roberts recommends that the Quarterly Bulletin on Solar Activity resume publication of solar data for the central region, discontinued in December 1938, and that the central region data for the period 1938 to the present be compiled and published. (6) A. D. Fokker recommends to publish spectral diagrams of type IV bursts on a regular basis. (7) A. D. Fokker has pointed out some highly desirable research activities to be carried out in the study of solar radio events: (a) Observations should aim at a more precise determination of the spectral profile of individual type I bursts. (b) Two-dimensional position determinations of individual stormbursts and determinations of their angular sizes will be most rewarding. (c) It is desirable that more detailed information on source sizes be obtained for all types of solar radio events and at several frequencies. (d) It is desirable to extend determinations of polarization ellipses for type III bursts to such an extent that, for one and the same burst, polarimetric observations be available at more than two different frequencies. (d) A knowledge of the actual form of the intensity curve of impulsive microwave bursts in its rising part may well be important for an understanding of the explosive phase of the flare phenomenon. {f) There is still a great want of more data on source positions and polarizations of type IV emission. BIBLIOGRAPHY

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Valnicek, B. 1964b, Bull. astr. Inst. Csl., 15, 207. Valnicek, B. 1965a, Publ. astr. Inst. Czech. Acad. Sci., 51, 62. Valnicek, B. 1965b, Bull. astr. Inst. Csl., 16, 258. Valnicek, B., Kleczek, J. 1964, Appl. Opt., 3, 1383. Valnicek, B., Kleczek, J., Topol, F. 1965, Bull. astr. Inst. Csl., 16, 44· 1965, J. geophys. Res., 70, 5737· Van Allen, J. A., Krimigis, S. M. 1964, J. geophys. Res., 69, 4481. Van Allen, J. A., Lin, W. C., Leinbach, H. Van Allen, J. A., Frank, L.A., Maehlum, B., Acton, L. W. 1965, J. geophys. Res., 70, 1639. Van Nieuwkoop, J. 1964, Nature, 201, 380. Van't Veer, F. 1965, in The Solar Spectrum (ed. C. de Jager), p. 257. Van't Veer, F. 1966a in Proc. of the Meeting on Sunspots, Florence, p. 150. Van't Veer, F. 1966b, Ann. Astrophys., 29, 7 and II9. Van't Veer, F. 1966c, Ann. Astrophys., 29, 223. Van't Veer-Menneret, C., Van't Veer, F. 1965, Ann. Astrophys., 28, 1026. 1966, Kosm. Issled., 4, 748. Vasilev, B. N. Vernov, S. N., Logachev, Y. 1., Lyubimov, G. P., Nikolaev, A. G., Gorchakov, E. V., Pereslegina, N. V., Vakulov, P. V. 1966a, Space Res., 7, in press. Vernov, S. N., Chudakov, A. E., Vakulov, P. V., Logachev, Y. 1., Lyubimov, G. P., Nikolaev, 1966b, presented at the Inter-Union Symp. on solar terr. Phys., A. G., Pereslegina, N. V. Belgrade, in preparation. Vernov, S. N., Chudakov, A. E., Vakulov, P. V., Logachev, Y. 1., Lyubimov, G. P., Pereslegina, N. V. 1966c, presented at the Inter-Union Symp. on solar terr. Phys., Belgrade, in preparation. Vinogradov, Y. I. 1964, Izv. Krym. astrofiz. Obs., 32, 67. 1965a, Izv. glav. astr. Obs. Pulkovo, 24, no. 178, 49· Vitinsky, Y. I. Vitinsky, Y. I. 1965b, Geofiz. Bjull. mezhduved. geofiz. Kom. Akad. Nauk SSSR, no. 16, 6o. Vitinsky, Y. I. 1965c, Soln. Dann. Bjull., no. II, 62, and no. 12, 53· Vitinsky, Y. I. 1966, Morfologia soln. Aktivnosti, Nauka Moskva. Vitinsky, Y. 1., Ihsanov, R.N. 1964a, Soln. Dann. Bjull., no. 7, 66. Vitinsky, Y. 1., Ihsanov, R.N. 1964b, Soln. Dann. Bjull., no. 10, 57, and no. 12, 63. 1966, presented at the Inter-Union Symp. on solar terr. Vitkevich, V. V., Vlasov, V. I. Phys., Belgrade, in preparation. Vladimirsky, B. M. 1964, Izv. Krym. astrofiz. Obs., 31, 271. 1965a, Izv. Krym. astrofiz. Obs., 33, 151. Vladimirsky, B. M. 1965b, Izv. Krym. astrofiz. Obs., 34, 305. Vladimirsky, B. M. 1964, Izv. Krym. astrofiz. Obs., 32, 46 (also in Izv. Vladimirsky, B. M., Pankratov, A. K. Akad. Nauk SSSR, 28, 2019). 1966, lzv. Krym. astrofiz. Obs., Vladimirsky, B. M., Pankratov, A. K., Stepanyan, A. A. 35. 222. von Kliiber, H. 1966, in Solar Physics, Lagonissi Summer Course, John Wiley and Sons, New York, in press. 1965, Soln. Dann. Bjull., no. 9, 57· Voyhanskaya, N. F. 1966, Astr. Zu., 43, 413. Voyhanskaya, N. F. Vsechsvyatsky, S. K. 1964, Geomagn. Aeronom., 4, 328. Vsechsvyatsky, S. K., Gurtovenko, E. A., Dziubenko, N. 1., Ivanchuk, V. I. 1966, Soln. Dann. Bjull., in press. 1965, Izv. glav. astr. Obs. Pulkovo, 24, no. 178, 26. Vyalshin, G. F., Krat, V. A. Waddington, C. J., Freier, P. S. 1965, J. geophys. R ., 70, 230. 1964, Z. Astrophys., 59, 205. Waldmeier, M. Waldmeier, M. 1966, in Proc. of the Meeting on Sunspots, Florence, p. 41. Wallis, G. 1965a, Publ. astr. Inst. Czech. Acad. Sci., sr, 145. 1965b, Publ. astr. Inst. Czech. Acad. Sci., 51, 184. Wallis, G. Ward, F. 1966, Astrophys. J., 145, 416. Warwick, C. S. 1964, in AAS-NASA Symp. on Physics of Solar Flares, p. 27. Warwick, C. S. 1965a, Astrophys. J., 141, 500. Warwick, C. S. 1965b, Astrophys. J., 142, 767.

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z.

SVESTKA,

President of the Commission

12. COMMISSION DE LA RADIATION ET DE LA STRUCTURE DE L'ATMOSPHERE SOLAIRE PRESIDENT: Dr R. Michard, Observatoire de Paris, Section d'Astrophysique, 92-Meudon, France. VICE-PRESIDENT: Dr M. N. Gnevyshev, Astronomical Observatory, Leningrad M-140, U.S.S.R. CoMITE n'ORGANISATION: R. G. Athay, M. G. J. Minnaert, E. A. Mi.iller, M. J. Seaton, Z. Suemoto. MEMBRES: Allen, Babcock, Billings, Blackwell, Blaha, Blamont, Bohm, Bohm-Vitense, Bray, Bri.ick (H. A.), Bruzek, Chamberlain, Christiansen, de Jager, Delbouille, Edlen, Edmonds, Elste, Evans (J. W.), Friedman, Giovanelli, Godoli, Gokdogan, Goldberg, Hotinli, Houtgast, Hubenet, Jager, Jefferies, Kawaguchi, Kiepenheuer, Kononovich, Kopecky, Laborde, Labs, Leighton, Locke, Loughhead, Li.ist, Mathias, Matsushima, Mattig, Mergentaler, Migeotte, Mugglestone, Namba, Neven, Newkirk, Nicolet, Peeker (J.-C.), Peeker-Wimel, Peyturaux, Pierce, Redman, Righini, Rigutti, Schroter, Severny, Sitnik, Sitterly, Sobolev (V. M.), Svestka, Swensson, Tandberg-Hanssen, Thomas (R. N.), Tousey, Unsold, Voigt, von Kli.iber, Waldmeier, Warwick (J. W.), Zirin, Zirker. INTRODUCTION Ce rapport et Ia liste bibliographique associee decrivent les progres realises dans I' etude de !'atmosphere solaire 'normale' de Janvier 1964 a Octobre 1966. Quelques travaux publies des 1963, mais malheureusement omis dans notre precedent rapport, ont ete indus. Le lourd travail necessaire pour passer en revue un domaine scientifique aussi vaste que celui de notre Commission a ete partage entre C. W. Allen (couronne), R. G. Athay (chromosphere) et R. Michard. Ce dernier adresse ses remerciements aux deux collegues qui l'ont aide si genereusement. Nous sommes particulierement reconnaissants a tous les membres de Ia Commission qui ont bien voulu nous adresser un compte rendu de leurs travaux ou de ceux de leurs collegues afin de rendre notre revue plus actuelle et plus vivante. REFERENCES GENERALES Notons les divers symposiums organises recemment sur des sujets interessant Ia Commission: -The Solar Spectrum, Symposium d'Utrecht, 1963 (1). -Stellar and Solar Magnetic Fields, Symposium no. 22 de l'UAI, Rottach-Egern, 1963 (2). -Astronomical Observations for Space Vehicles, Symposium no. 23 de l'UAI, Liege, 1964 (3)· -Abundance Determinations in Stellar Spectra, Symposium no. 26 de l'UAI, Utrecht, 1964 (4)· -Campi magnetici solari e la spettroscopia ad alta risoluzione, Rome, 1964 (9), l'une des nombreuses manifestations organisees pour le 4eme Centenaire de la naissance de Galilee. - Cosmical Gas Dynamics, Symposium no. 28 de l'UAI, Nice, 1965 (5). -First Harvard-Smithsonian Conference on Stellar Atmospheres, Cambridge, 1964 (7). -Second Harvard-Smithsonian Conference on Stellar Atmospheres, Cambridge, 1965 (8). 197

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-Solar Physics, an Advanced Study Institute sponsored by NATO, Lagonissi, 1965 (6). -The Fine Structure of the Solar Atmosphere, Anacapri, 1966 (1o), organise pour !'inauguration du telescope solaire de la station d' Anacapri du Fraunhofer Institut. Les references ulterieures a ces symposiums et colloques seront donnees sous la forme (RG n) n etant le numero d'ordre de la publication dans la liste de References Generales. Un traite intitule 'Astrophysique et Astronomic Stellaire' est publie par l'Academie des Sciences de l'U.R.S.S. Le tome III contient une description de la physique solaire par cinq specialistes eminents. Une monographic sur la couronne solaire et le rayonnement corpusculaire dans l'espace interplanetaire a ete editee sous la direction de Vsekhviatsky (n). Un excellent livre sur la couronne a ete recemment publie par Billings (12). LE SPECTRE CONTINU SOLAIRE

Les efforts pour parvenir a une courbe d' energie precise du continuum solaire au centre du disque se poursuivent activement. Labs annonce une publication (1) recapitulant l'ensemble des resultats de son programme. Une calibration en unites absolues du continuum adoptee dans les Atlas photometriques du spectre solaire de l'Observatoire d'Utrecht et de l'Observatoire de Gottingen sera etablie. Peyturaux a termine en 1965 ses comparaisons de Solei! au corps nair pour le domaine spectral visible, mais seuls des resultats preliminaires ant ete publies (2). L'extension de ces mesures absolues jusqu'a 15 fL est prevue. En U.R.S.S., l'Institut Sternberg est particulierement actif dans ce domaine. Murashova et Sitnik (3) donnent les resultats d'une serie d'observations obtenues en 1957-59 et les comparent a ceux de 1952-55. Ulterieurement Sitnik combine ses resultats en une courbe unique pour,.\,\ 328o-12 5ooA (4) et presente des mesures dans l'IR (2·7 to 5 fl.) (5). II discute de la meilleure methode pour controler la stabilite de la transparence du ciel (6). Enfin de nouvelles observations pour A.A. 31oo-66ooA sont effectuees par Makarova (7). Le meme auteur a discute les donnees disponibles, lesquelles presentent des ecarts systematiques tres importants (8). Lambert et Willstrop (9) ant cherche a etablir la courbe d'energie solaire en combinant leurs mesures absolues des etoiles avec la magnitude V et la couleur B- V du Solei!. Houtgast (1o) a publie les resultats de ses mesures absolues portant sur 32 'fenetres' du domaine 300o-4oooA. II trouve une discontinuite de Balmer lllog I ::::: o·o3 en contradiction avec la valeur 'classique' d'environ 0·12. Un grand interet s'attache a !'extension de la courbe d'energie solaire a l'IR lointain, ce qui necessite des observations en ballon. Les resultats deja obtenus par Murcray et al. (n) et par Beer (12) indiqucnt que la temperature de brillance moyenne du disque solaire decroit de 5400° a 4270° entre A. = 4 fL et A. = 1oo fL· L'assombrissement centre-bard dans l'IR constitue un test tres sensible du modele thermique des couches superieures de la photosphere. Des predictions ont ete faites pour divers modeles par Lena (13) et par Noyes et al. (14). Pour !'instant les mesures disponibles ne s'etendent que jusqu'a 10·2 fL (Pierce) mais imposent deja des limitations strictes aux modeles. Le meme probleme peut etre etudie par !'analyse du continuum UV mais la theorie du coefficient d'absorption est alors plus difficile (cf. Matsushima, RG 7). Blamont et Bonnet (15) ont trace les courbes d'assombrissement a 288o, 266o et 219oA grace a des images en lumiere filtree obtenues en fusee. Des travaux plus recents du meme groupe montrent que le domaine spectral 300o-2oooA est accessible aux ballons sondes ce qui permet l'emploi d'instruments plus importants et mieux stabilises.

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La depression du continuum solaire a 2o8sA a ete discutee quantitativement par Kodaira (16) qui l'attribue a la discontinuite d'ionisation de AI 1 a partir du niveau 3p 2P0 • Be nouvelles mesures d'assombrissement dans le spectre visible et le proche UV ont ete obtenues au Pic du Midi par Mouradian (17), elles s'etendent jusqu'a /L = 0"10. Le meme auteur (loc. cit.) a applique la methode d'Unsold lors de !'eclipse partielle du 15 Fevrier 1961 pour determiner le profil du bord lui-meme. Les resultats demeurent assez incertains mais Ia methode pourrait conduire a de bons resultats si les observations etaient obtenues par 'tres bonnes images', comme ce fut le cas au Pic du Midi le 20 Mai 1966 (Rosch, RG 10). Diverses methodes de determination du profil du bord par photometric d'une portion de croissant au voisinage des contacts interieurs d'une eclipse totale ont ete appliquees par Kristensen (18) et par Heintze (19) (ainsi que par plusieurs experimentateurs a !'eclipse du 20 Mai 1966). Ce dernier auteur trouve un anneau brillant assez prononce, ce qui le conduit a un modele pour lequel le minimum de temperature se situe a une profondeur optique assez grande, T 5000 = - 0.07. Ce modele est incompatible avec l'assombrissement centre-bord a 10 p,. La question d'eventuelles differences thermiques entre les poles et l'equateur du Solei! continue d'etre a l'ordre du jour, les observateurs employant d'ailleurs aussi bien des mesures des largeurs equivalentes et intensites centrales des raies de Fraunhofer que des mesures du continuum, comme critere de temperature. Selon Mulders et Slaughter (:zo), l'ecart thermique eventuel est insignifiant. II en est de meme pour Appenzeller et Schroter (21) qui donnent une limite superieure de 6°. Un programme de comparaison pole-equateur a ete entrepris par Houtgast (non public). Les remarques de K. H. Bohm (cf. Rapport precedent) sur le contenu d'information des lois de variations centre-bord de l'intensite emergente ont donne lieu a quelque controverse (22, 23). Par ailleurs une elegante methode d'inversion de Ia relation 1 (p,) ~ S (T) a ete proposee par Delache (24). Notons enfin que les travaux recents d'interpretation du continuum solaire ont beneficie des nouveaux calculs detailles des coefficients d'absorption continue effectues par Bode (25). ATLAS ET TABLES DU SPECTRE DE FRAUNHOFER.

IDENTIFICATIONS

Mrs Moore-Sitterly annonce que Minnaert, Houtgast et elle-meme . . . 'have now concluded our publication of the Second Revision of Rowland's preliminary table of solar spectrum wavelengths. This compendium is in press and should be in print before 1967. The title is "The Solar Spectrum 2935A to 877oA". It contains approximately 24 ooo lines, and includes a number of new lines. Measured equivalent widths from the records of the Utrecht Photometric Atlas replace the Rowland estimated line intensities. Reduced widths derived from these directly measured equivalent widths are listed. Other columns indicate the spot behavior of the atomic lines, and give revised identifications as to chemical origin of the lines. For classified atomic lines the lower excitation potential and multiplet number are listed. For molecular lines the rotation branch and quantum number, and the vibration band are indicated. Complete band designations are entered in notes. About 73% of the lines are wholly or partially identified. This volume will appear as Monograph 61 of the National Bureau of Standards (349 pp).' La preparation du nouvel atlas photometrique du spectre solaire, commencee par Delbouille, Neven et Roland a I' aide du spectrometre a double passage installe au Jungfraujoch par l'equipe de l'Institut d' Astrophysique de Liege, est tres avancee. Un rapport special sera presente a Ia Commission par les auteurs. A Kitt Peak, on a entrepris une nouvelle determination de l'echelle des longueurs d'onde du Catalogue de Rowland revise et de son extension a l'IR. Pierce annonce en outre Ia publication d'un catalogue de plusieurs milliers de raies observees en emission a 1' extreme bord du Soleil, raies dont Ia plupart sont dues aux terres rares. u

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II est clair que I' exploration du spectre solaire ne sera jamais achevee, car toute amelioration technique (resolution, rapport signal/bruit du recepteur photographique ou photoelectrique) fait apparaitre des raies nouvelles. Sur un spectre obtenu a Sacramento Peak et couvrant seulement sA (5047·2-5052·9) !'auteur de ce rapport a compte 22 raies qui ne figuraient pas dans la Premiere Revision du Catalogue de Rowland! Un travail systematique de recherche des raies faibles est du a Ahmad Kiasatpoor qui a publie pour le domaine ,\,\ 6ooo-7ooo un catalogue contenant de tres nombreuses raies nouvelles (1). Blackwell nous annonce !'obtention a Oxford de spectres solaires ou le rapport signal/bruit est pousse jusqu'a la limite imposee par le nombre de photons. On assiste a un regain d'interet pour le probleme de !'identification des raies du spectre de Fraunhofer. Grace a de nouvelles donnees de laboratoire, Swensson (2) a revise !'identification du spectre de Mg I et attribue a cet atome 91 raies solaires jusqu'alors non identifiees. Le meme auteur trouve 26 raies de pI dans le proche IR (3) et etudie les raies de l'azote dans le meme domaine spectral (3 bis). Grevesse (4) discute de !'identification du bismuth. La presence de raies interdites dans le spectre de Fraunhofer a ete abondamment etudiee. Kodaira (5) considere le cas de [Fe u]. Les raies predites de cet element ont ete systematiquement recherchees par J.P. Swings sur des enregistrements photoelectriques a haute resolution obtenus au Jungfraujoch: une vingtaine de raies tres faibles peuvent etre attribuees a [Fe 11] et deux autres a [Ni u] (6, 7). Les observations modernes mettent en evidence des particularites interessantes du spectre de Fraunhofer. Ainsi des depressions diffuses a 6362, 6344 et 63r9A sont attribuees par Mitchell et Mohler a des multiplets de Ca I en presence d'auto-ionisation a partir du niveau superieur (8). Selon Swensson (9), les profils larges et complexes de certaines raies de Mn I vers 87ooA peuvent etre expliques par la structure hyperfine. Aller indique que les profils des raies de C I dans le visible sont anormalement larges, CC qui pourrait etre du a la formation de quasi-molecules CH. L'etude spectroscopique du Soleil dans l'UV et l'EUV se poursuit activement et de grands progres ont ete faits dans !'identification de ce domaine spectral. Une revue recente est due a Tousey et a!. (RG 3). Comme le spectre d'emission de l'EUV est du a la couronne ou a la couche de transition, on trouvera de nombreuses references sur ce domaine spectral dans les parties de ce rapport consacrees aux couches exterieures de 1' atmosphere solaire (cf. ci-dessous). Pottasch (1o) a prepare une revue tres detaillee des problemes de !'interpretation du spectre EUV. Goldberg eta!. (n) discutent la question de !'identification de CO dans l'UV. II est particulierement satisfaisant que de nouvelles equipes scientifiques de divers pays soient maintenant en mesure de contribuer a la spectroscopic 'spatiale' du Soleil. De bons spectres du domaine zsoo-roooA ont ete obtenus par Black et al. (12). Par la suite la meme equipe de Culham Laboratory a reussi a photographier le spectre de la chromosphere-couronne de Sso a 295oA, la fente etant maintenue a ro" du limbe avec une precision de z". Le spectre montre un continuum chromospherique et de tres nombreuses raies d'emission dont !'identification est en cours; des resultats preliminaires ont ete publies par Burton et Wilson (13)· En Grande-Bretagne egalement, une equipe de l'Universite de Leicester a obtenu de remarquables resultats dans la spectrographic des rayons X solaires (region 25-11 A). L'Observatoire d'Utrecht a developpe un spectrometre de resolution elevee pour le domaine 44-64A. Enfin en France, Bonnet (Service d' Aeronomic du CNRS) a obtenu le spectre du limbe solaire dans le domaine 3000-1900A a l'aide d'un coronographe em barque sur fusee-sonde. LONGUEURS D'ONDE.

ROTATION.

CIRCULATION.

La question des longueurs d'onde des raies de Fraunhofer sous l'effet de la rotation de l'astre, du deplacement relativiste et des diverses autres causes de decalages systematiques, a

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fait !'objet de nombreux travaux en U.R.S.S. De nouvelles observations spectroscopiques de la rotation solaire ont ete effectuees par Aslanov (I, 2). Le meme auteur a prepare un 'Catalogue des deplacements et des profondeurs optiques des raies de Fraunhofer dans !'atmosphere solaire' (3) en vue de l'etude du deplacement relativiste (4, s). La discussion de Melnikov (6) montre que les variations systematiques du decalage des raies avec leur intensite, le potential d'excitation et la longueur d'onde peuvent se ramener a un effet de hauteur dans !'atmosphere solaire, lie aux variations du champ de vitesses. Apres correction de cet effet on obtient un parfait accord avec la theorie de la relativite. Dans un travail deja cite plus haut, Appenzeller et Schroter ont obtenu la variation centrebard des longueurs d'onde de plusieurs raies. Roddier (cf. ci-dessous) a mesure le profil des raies de resonance de Sr I, Ba I et Ca I par la methode du jet atomique dans une echelle absolue de longueur d'onde. 11 serait sans doute tres utile d'etendre des mesures de ce type a un grand nombre de raies, car les problemes des 'longueurs d'onde', des profils asymetriques et de la structure heterogene de !'atmosphere solaire sont indissolublement lies. 11 est interessant de signaler ici les travaux relatifs a Ia circulation generale des couches superficielles du Solei!, bien que ces mouvements semblent difficiles a mettre en evidence par la spectroscopic et ne soient reveles que par !'analyse du mouvement des taches. Une telle analyse a ete effectuee par Ward (7, 8, 9) qui montre la presence d'une correlation marquee entre les mouvements prop res en latitude et longitude des taches (donnees de Greenwich) et presente un modele de circulation sans symetrie axiale constitue d'un ensemble d' 'ondes' qui transportent uncertain moment angulaire de l'equateur vers le pole. Les aspects energetiques de ce modele ont ete discutes par Starr et Gilman (IO, II). La theorie de la rotation differentielle, basee sur !'hypothese de Biermann qui l'attribue ala viscosite non isotrope des elements turbulents dans la zone convective, a ete developpee par Sakurai (xz); il critique le traitement anterieur de Kippenhahn et aboutit a un bon accord avec la loi de rotation observee. La theorie de Ia rotation dans les couches internes du Solei! en equilibre radiatif a ete traitee par Rubashev (IJ), par integration numerique des equations exprimant le bilan du moment angulaire (equations de jeans). LA PHOTOSPHERE

(a) Granulation. Structures cinematiques et magnitiques Le nombre des recherches experimentales nouvelles sur la granulation est relativement faible, sans doute parce que tousles specialistes sont conscients de !'extreme difficulte d'obtenir des documents suffisamment bons pour meriter une etude quantitative! Le point des connaissances actuelles sur la granulation a ete fait dans une monographic de Bray et Loughhead (I). A Poulkovo, Vassiljeva et Yudina (:z) ont mesure photoelectriquement les fluctuations de brillance de la surface solaire simultanement pour deux longueurs d'onde AI et A2: la correlation entre les fluctuations observees decroit fortement quand l'ecart A2 - AI augmente. Ce resultat est confirme par Krat et Petrova qui utilisent une technique photographique (J). Ces auteurs esquissent une explication basee sur la propagation de perturbations de longueur d'onde 103 km a partir des elements convectifs. Cependant, les deux methodes ayant une constante de temps tres courte, il n'est pas impensable que des effets de distorsion aleatoire de l'image due a !'atmosphere terrestre affectent les resultats. Le spectre de puissance a deux dimensions (frequences spatiale et temporelle) a ete determine par Levy (4) a !'aide d'un excellent film de granulation obtenu au Pic du Midi. Dans ce travail, les effets de distorsion atmospherique evoques ci-dessus se sont reveles tres genants et limitent ia signification des resultats aux hautes frequences spatiales. L'auteur

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confirme la presence d'une faible composante oscillatoire dans les fluctuations de brillance de la photosphere, composante dont !'existence probable a ete annoncee par Edmonds et McCullough (5). Rosch (RG 10) a presente de remarquables images de la granulation obtenues au Pic du Midi lors de !'eclipse partielle du 20 Mai 1966. On pourra obtenir le 'profil instrumental' de la combinaison atmosphere-telescope grace a !'etude du bord lunaire et etablir ainsi une photometrie plus rigoureuse des granules. A Sacramento Peak, Beckers (RG 10) a etudie les fluctuations de brillance photospherique d'une echelle plus grande que la granulation. II obtient un spectre de puissance aux basses frequences spatiales qui ne montre aucune frequence privilegiee, contredisant ainsi les resultats anciens de Stuart et Rush, et suggerant que la supergranulation n'a pas d'effet sur le spectre continu photospherique. En revanche le phenomene cinematique de supergranulation a pu etre correle avec d'autres structures. Simon et Leighton (6) ont montre que les details brillants du reseau des spectroheliogrammes K 232 , ainsi que les champs magnetiques associes, tendent a apparaitre aux frontieres des cellules de la supergranulation. Celle-ci serait le resultat d'une convection non-stationnaire dont les elements refouleraient le champ magnetique a leur peripherie selon le mecanisme propose par Parker. Simon (RG 5) a mis en evidence les vitesses verticales faibles dans la photosphere aux frontieres des supergranules et a trouve (RG 10) que les granules sont entraines dans le mouvement general de la photosphere associe a la supergranulation. Quelques observations de la supergranulation ont ete obtenues a Meudon (7). L'etude du champ de vitesses verticales dans !'atmosphere solaire a ete etendu a la photosphere profonde par Edmonds, Michard et Servajean (8) qui ont etudie sur un film pris par Evans a Sacramento Peak les fluctuations de vitesse, intensite centrale et largeur equivalente pour la raie 5052 C 1, en correlation avec d'autres raies de niveaux plus superficiels. Outre les oscillations, une importante composante 'convective' est presente dans les couches profondes. Les mesures spatio-temporelles de vitesse radiale effectuees sur les films de Sac'Peak ont ete analysees a nouveau par P. Mein (9) qui a obtenu des spectres de puissance a deux dimensions directement comparables aux diagrammes diagnostiques de la theorie des ondes. Cette analyse confirme la separation en plusieurs composantes du champ de vitesses; elle montre !'absence de propagation horizontale des oscillations, question que I' auteur discute par une methode nouvelle. Edmonds etudie a nouveau sur plusieurs series de mesures le probleme des correlations entre vitesses verticales et granulation (1o). D'autre part il examine les ecarts a une loi gaussienne des fonctions de distribution des fluctuations de brillance et de vitesse de la photosphere. Ces ecarts sont faibles mais significatifs (II). Selon cet auteur, les variations des proprietes statistiques des structures fines solaires selon l'echantillon considere excedent les limites permises par divers criteres de signification, et l'on doit envisager des variations locales ou temporelles de ces proprietes. Dans ce sens, Orrall (12) a montre que les proprietes des oscillations photospheriques sont pratiquement les memes dans les regions brillantes du reseau K 232 (autre que les plages proprement dites) que dans les regions normales. Ulterieurement (13), il a etudie les vitesses radiales dans la raie K 3 elle-meme, obtenant leur spectre de puissance qu'il compare avec les donnees relatives aux raies de profondeur de formation superieure. Les structures chromospheriques dans les raies de Balmer et H et K sont aussi discutees par Sivaraman et Vainu Bappu (non publie) et par Dodson-Prince et Mohler (RG 10). L'etude de Ia structure fine des champs magnetiques dans !'atmosphere solaire hors des regions actives a ete poursuivie par plusieurs auteurs. Vasiljeva (14) etudie ces structures du point de vue statistique: fluctuations de vitesses et fluctuations magnetiques ne sont pas

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correlt~es. Krat et Vjalshin comparent les champs et les vitesses en H f3 (IS). A Kitt Peak, Livingston a mesure simultanement la structure du champ en H a et 6569 Fe I; pour le domaine 5 < H < Ioo gauss les champs photospherique et chromospherique sont parfaitement correles et egaux. Des observations a tres haute resolution de Beckers et Schroter confirment que, loin des regions actives, le champ fluctuant est concentre en points isoles de 3 a s" ayant un champ de plusieurs dizaines de gauss, non correle aux vitesses radiates ou a Ia granulation photospherique (I6). Une attention particuliere a ete portee aux champs polaires. Severny decrit ainsi ses resultats (I7, IS, I9): 'The examination of general magnetic field of the Sun carried out with high resolution (2" X s") showed that there exists no coherent field. General m.f. of the Sun consists of a number of small (5" of arc and less) elements of different polarity, field strengths and size. The net (mean) magnetic field on S-pole were absent since the summer I963 up to September I964, when weak m.f. of N-polarity appeared ( + I, I gauss). On the northern polar cap and in northern hemisphere the field of S-polarity predominated for this period with the mean strength 4-5 gauss. The net magnetic flux at N-pole and in N-Hemisphere was negative due to the larger sizes of S-elements in N-Hemisphere, so that the ratio of these fluxes were:

F_(N) : F+(N) : F_(S) : F+(S)

= 2 :

o,5 :

I : I.

'In I965 this ratio was variable and the net flux for the whole disk was sometimes negative or positive. The observed distribution of general m.f. with latitude cannot be described by a dipole field or by the field of uniformly magnetized sphere.' Cette description est pleinement en accord avec les resultats de Livingston (20), Grigorjev et Stepanov (2I) et Stenflo (22). Bumba et al. (26) ont utilise les magnetogrammes du Mount Wilson pour calculer comment le Soleil apparaitrait en tant qu' etoile variable magnetique vue dans son plan equatorial. Des revues de la question des structures fines de !'atmosphere solaire ont ete publiees par Michard (23) (RG 6) et par Noyes (RG 5). Dans la reference (RG 5) on trouvera aussi d'importantes mises au point theoriques par Spiegel, Bohm, Moore, Lighthill, Rybicki. On notera aussi la revue de Pikelner (24) et, sur la question des champs magnetiques, celle de Severny (25). Dans le present rapport, les travaux theoriques sont plus specialement traites dans un paragraphe ulterieur. (b) Profils et largeurs equivalentes des raies de Fraunhofer

Les problemes evoques dans les paragraphes (b) (c) (d) de ce rapport sont evidemment etroitement lies. Nous n'avons pu eviter un certain arbitraire dans Ia repartition des travaux cites entre ces trois rubriques. De Jager et Neven (I) ont termine leur programme d'enregistrement au spectrometre du Jungfraujoch des profils de 50 raies environ du proche IR, observees pour 6 positions sur le disque, de fk = 0'30 a fk = I. Les memes auteurs et Namba ont etudie le profil de IO 830 He I sur Ia photosphere normale (2). Les resultats sont interpretes a l'aide d'un modele heterogene de Ia chromosphere. Le delicat probleme de Ia correction de l'effet du profit instrumental est discute par De Jager et Nevcn (3). Les donnees sur les profils du multiplet IO 700 C I de fk = I a fk = o·3 publiees par ces memes auteurs (4) leur ont servi d'exemple pour exposer une methode d'analyse 'empirique' des profils qui permet en principe de determiner un parametre de macroturbulence (modele a 2 colonnes), l'abondance, l'amortissement, la fonction-source et la microturbulence (s). La macroturbulence est tiree de l'asymetrie des profils par une procedure un peu sommaire

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dont Ia validite a ete discutee par Kulander et Jefferies (6). Les longueurs d'onde precises de ce meme multiplet de c I ont ete determinees a Gottingen par Bruckner. Olson (zo) a discute Ies asymetries observees des raies de Fe I, 0 I et C I (donnees de Jager et Neven). II montre que les oscillations photospheriques ne jouent qu'un role negligeable dans l'asymetrie. Un modele de vitesses convectives variables avec Ia profondeur rend compte de I' ensemble des observations. Les profils des raies de Balmer H cc a H ont ete mesures, au centre du disque et au bord (sin 8 = o·99), et discutes par Kuli-Zade (7) qui obtient un bon accord entre observation et theorie. Le meme auteur (8) a effectue des observations similaires pour diverses raies tres fortes du spectre de Fraunhofer: raies D de Na I, b de Mg I, 4227 Ca I, 3944 et 3961 AI I, H et K (voir aussi les references (9) et (10). Khetsuriani (n) a publie de nouvelles mesures photoelectriques des profils de 7 raies de Paschen ainsi que de Ia raie Brackett y pour plusieurs positions sur Ie disque. A Gottingen, Bubke a mesure photoelectriquement en fonction de sin (J les intensites centrales des raies du multiplet a3F- y 3F 0 de Fe I (12). II en deduit Ia variation de Ia temperature d'excitation avec Ia profondeur optique, temperature qui passe par un minimum de 38oo a 3900° vers log To = - 5·7. Voigt a aussi mesure les intensites centrales de raies de Ba I et II, SrI et II, Eu I et II et des resultats preliminaires ont ete publies (IJ).

o

Une nouvelle courbe de croissance pour le centre du disque solaire a ete determinee par Cowley et Cowley (14) qui emploient les forces d'oscillateur de Corliss-Bozman et les largeurs equivalentes de 6I2 raies determinees photoelectriquement a l'Observatoire MacMath. E. A. Muller, Baschek et Holweger signalent qu'un programme d'observations centre-bord et d'analyse des profils de raies permises et interdites de l'oxygene est en voie d'achevement: les auteurs cherchent a determiner le modele thermique et le modele de turbulence qui rendent compte au mieux des observations. Une comparaison entre modeles et observations des largeurs equivalentes de quelques raies de Ti a ete effectuee par Nissen (15). L'etude des bandes moleculaires du spectre de Fraunhofer a ete l'objet de bien des travaux au cours des trois dernieres annees. L'article de Schadee (16) sera tres utile car il rassemble sous une forme claire et complete Ia plupart des notions physiques et des methodes astraphysiques necessaires a Ia discussion des spectres moleculaires dans le Solei!. En outre il passe en revue les identifications de nombreux composes dans le spectre de Ia photosphere normale en tenant compte de criteres bases sur les intensites pro babies des raies correspondantes. Les largeurs equivalentes de raies de CH au centre du disque ont ete mesurees par Ruzickova-Topolova (17) qui determine une temperature de rotation. Withbroe (r8) a effectue, toujours pour Ia bande G de CH, un travail plus etendu comportant Ia mesure photoelectrique des largeurs equivalentes, mais aussi des profils de raies bien isolees, en fonction de Ia position sur le disque. Les observations peuvent etre interpretees dans I' hypothese de l'ETL a l'aide d'un modele thermique du a Elste et d'un modele de turbulence. Poletto et Rigutti ont etudie (19) deux bandes du systeme rouge de CN: ils trouvent une temperature de rotation et tentent une estimation de Ia force d'oscillateur de Ia transition electronique correspondante. A Kodaikanal, Nirupama Raghavan a observe photoelectriquement pour divers sin (J les profils de raies choisies de CN et C2 : il analyse les largeurs en termes de microturbulence et trouve une vitesse presque isotrope de 3 km s-1 (non publie).

(c) Thiorie du spectre de Fraunhofer Une grande partie des travaux dans ce domaine continuent d'etre centres sur le probleme des ecarts a l'equilibre thermodynamique local (ETL), qui peut etre considere de deux points de vue differents:

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-recherche empirique de contradictions auxquelles pourrait conduire !'approximation de l'ETL, et influence de cette approximation sur la determination de diverses caracteristiques de !'atmosphere (en particulier les abondances); -analyse theorique directe grace a la solution simultanee des equations de 1' equilibre statistique et des equations de transfert; la comparaison ulterieure aux observations permet de tester les diverses hypotheses de la theorie et le choix du modele d'atmosphere. Cette derniere approche est utilisee dans le cas des raies de Na I par Johnson (1) qui montre que l'ecart a l'ETL est tres faible dans la photosphere: les temperatures d'excitation trouvees empiriquement par le meme auteur ne sont pas explicables par la theorie. Le probleme a ete repris par Chamaraux (2) qui obtient un bon accord entre profils calcules et profils observes pour les raies D. Selon Mugglestone (RG 8) le centre de ces raies est tres influence par les ecarts a l'ETL. L'analyse empirique des profils des memes raies D permet a Curtis (RG 8) de determiner les fonctionS-SOurCeS dans }a raie et le COntinuum qui Se revelent egales pour T (5000) > Q•QI. Par ailleurs Curtis determine un parametre d'elargissement Doppler tres faible, explicable par le seul elargissement thermique en !'absence de toute turbulence appreciable.

Une analyse similaire a ete faite pour le multiplet b de Mg I par Henoux (3) d'apres les profils observes en fonction de la position sur le disque par Waddell. La fonction-source est bien determinee, mais le coefficient d'elargissement Doppler n'est pas en accord avec celui de Curtis. D'autre part Henoux a mesure les profils dans la basse chromosphere (h < 1 soo km) et cherche a les interpreter avec la fonction-source obtenue sur le disque: les contradictions rencontrees ne pourraient etre levees que par un modele heterogene de la basse chromosphere. A propos de ces etudes empiriques des multiplets, notons qu'une controverse theorique sur la question de I' egalite des fonctions-sources dans les raies d'un multiplet a oppose Waddell et Athay (cf. les references dans le chapitre sur Ia Chromosphere). Pour en revenir au traitement theorique, notons !'analyse des raies de resonance de Ca rr et Mg II par Dumont (4), qui d'autre part perfectionne le traitement numerique du transfert hors ETL pour tenir compte de l'amortissement (5). Le cas de l'hydrogene est traite par Cuny (6) ainsi que par plusieurs autres auteurs (RG 7) dans le cadre d'une analyse theorique de l'atome a 3 niveaux. La discussion empirique de !'approximation de l'ETL pour les raies metalliques a ete consideree par de nombreux auteurs dans le cadre des recherches sur les abondances (cf. ci-dessous). lei nous noterons plus specialement l'etablissement par Holweger (7) d'un modele empirique de la photosphere et de la basse chromosphere base sur les intensites centrales des raies de Fraunhofer: le modele obtenu est a temperature constamment decroissante jusqu'a r (sooo) :::: ro- 6 (T = 3900°). L'emploi d'observations et de valeurs f recentes conduit a des resultats compatibles avec !'approximation de l'ETL. L'etude des largeurs equivalentes conduit aussi Teplitskaya (8) et Pagel (RG 8) a des temperatures d'excitation tres voisines des temperatures electroniques adoptees. Mitropolskaya (9, 10, n) applique Ia theorie de l'elargissement par effet Stark et effet de pression a ses observations des profils des raies de l'hydrogene H IX et H {3, Paschen {3 et Brackett y. Un accord raisonnable est obtenu avec le modele classique de de Jager; le cas des raies de Balmer dans les facules est aussi traite. Pande et Sitnik (12) et Pande (IJ, 14) ont etudie les raies des bandes de CO dans la photosphere et insistent sur le fait que les molecules CO sont concentrees au voisinage du minimum de temperature. Les observations nouvelles (14) conduisent a une temperature de rotation pour CO.

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Rachkovsky a poursuivi l'etude du transfert dans les raies en presence d'un champ magnetique (IS)· Le calcul numerique (I6) conduit a des ecarts significatifs entre les resultats de la theorie de Unno et de celle de !'auteur. La discussion des profils des raies de Fraunhofer peut etre amelioree ou simplifiee de diverses manieres. On notera une discussion de la representation du profil des ailes des raies fortes par Gussman (I7) qui critique la formule a deux parametres de Mattig et Schroter et lui prefere une formule a un seul parametre. Le meme auteur (I8) presente une modification de la methode des fonctions de poids permettant de simplifier son emploi. Enfin, bien qu'il porte sur le cas stellaire, nous citerons ici un travail de Traving (I9) qui etudie }' effet SUr }a COUrbe de Croissance d'une epaisseur optique LJ T finie des elements turbulents de !'atmosphere: il s'agit la d'une tentative bienvenue pour depasser les concepts classiques de micro- et macroturbulence ou AT est supposee nulle ou infinie.

(d) Abondances des elements Dans la mesure ou un effort plus grand est fait pour la mesure des forces d'oscillateurs, Ia determination de valeurs plus precises des abondances des elements dans le Solei! devient possible et est activement poursuivie. Ainsi les valeurs f de Corliss, Bozman et Warner ont ete employees par Goldberg et al. (I) a une nouvelle estimation de l'abondance de Fe I. Leftus (z, 3) etudie en detaille cas du titane. Moyennant l'emploi des donnees les plus recentes sur les forces d'oscillateurs, les spectres de Ti I et Ti n conduisent aux memes abondances, et }'approximation de l'ETL semble tout a fait acceptable. Nous avons rec;u d'Aller un rapport sur un programme important de determination des abondances dans le Soleil et certains types d'etoiles, programme auquel participent plusieurs astronomes. Les donnees solaires sont des profits mesures, avec double passage sur le reseau, par Mitchell et Mohler (4) aux Observatoires MacMath et du Mount Wilson. Le programme comporte une etude approfondie des causes d'erreurs d'ordre physique (valeurs f) et astraphysique: cf. Aller et al. (S) et la revue detaillee de Aller (6). Mugglestone et O'Mara (7) ont montre que l'elargissement par amortissement (effet Stark et effets de pression) peut jouer un role notable dans l'estimation des abondances, ce qui conduit a rejeter la methode des fonctions de poids. Les auteurs preferent le calcul complet des profils a l'aide de deux modeles thermiques extremes avec variation de l'abondance jusqu'a ce que le profil calcule s'accorde au profil observe. Pour le cas des raies faibles ou l'on rencontre souvent le probleme des 'blends' la methode comporte egalement le calcul d'un spectre 'synthetique' couvrant !'ensemble du 'blend'. Aller note que 'the effects of uncertainties in the /-values mask the errors which may arise from the uncertainties in the model or theoretical treatment'. Ceci conduit a un programme de calculs quantiques des probabilites de transition, calculs tres difficiles mais possibles pour certains metaux comme AI et Mg: cf. Chapman et al. (8). Aller communique aussi des valeurs preliminaires d'abondances pour Ru, In, Au. Les abondances des terres rares ont ete etudiees par A. Righini et Rigutti (9) ainsi que par Wallerstein (10). De nouvelles mesures de largeurs equivalentes conduisent Grevesse (n) a reviser legerement l'abondance admise pour le strontium. Le lithium, represente seulement par sa faible raie de resonance fortement 'blendee' a 67o8A, pose un probleme interessant discute par Lynds (12). Cependant Dubov (IJ) a remarque que la raie 6708 est tres renforcee dans les taches solaires, ce qui permet une determination meilleure de l'abondance. La question a ete reprise par Schmahl et Schroter (14); une analyse soignee montre que l'abondance de Li est superieure a Ia valeur admise anterieurement; le rapport isotopique Li 6JLF est de l'ordre de 5%·

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E. A. Muller nous annonce les premiers resultats d'un programme etendu de recherches sur les abondances poursuivi en collaboration avec Mutschlecner. Le cas du nickel a ete traite par !'analyse des largeurs equivalentes observees en plusieurs positions sur le disque: une meme abondance represente correctement les spectres obtenus du centre au bord et les raies de divers potentiels d'excitation. D'autre part le meme auteur passe en revue les problemes des abondances solaires dans deux publications recentes (RG 4, RG 6). Sur Ia base d'observations et de donnees de laboratoire nouvelles, L. Herzberg, Delbouille et Roland montrent que les raies de C13N sont indecelables dans le spectre de Fraunhofer et obtiennent une limite inferieure du rapport Cl 2/C13 (x6). Gokdogan et Peeker (15) ont signale que deux multiplets de Fe I conduisent a des courbes de croissance distinctes, ce qui jetterait quelques doutes sur Ia determination des abondances par Ia methode classique. L'amelioration des observations et des forces d'oscillateurs disponibles tend a reduire les discordances que Peeker et ses collaborateurs attribuaient aux ecarts a l'ETL: mais Ia mise en garde demeure salutaire!

(e) M ode!es et theories de la photosphere et de la zone convective II n'existe pas actuellement de 'modele' de Ia photosphere susceptible de rendre compte de !'ensemble des faits d'observation. A fortiori n'existe-t-il pas de modele qui aurait en outre l'avantage d'etre base sur une interpretation physique complete et coherente. II est vrai que si un tel modele existait Ia physique de !'atmosphere solaire normale serait 'achevee'! Heintze et al (x) ont propose un nouveau modele empirique, le 'Utrecht Reference Model of the solar photosphere and low chromosphere' en vue de faciliter Ia comparaison et Ia discussion de resultats obtenus par !'analyse des divers types d'observations. II est certain que l'emploi d'un tel modele de reference presente des avantages considerables a condition que ce modele soit frequemment revise. Une premiere revision sera preparee a !'issue de discussions prevues pour 1967 d'une part a Utrecht (International Study Week on the Quiet Photosphere), d'autre part au sein de Ia Commission 12. L'equilibre radiatif dans Ia photosphere a ete discute par Waddell sur Ia base des observations du continuum solaire, en considerant le flux d'energie et aussi le flux de photons (2). Gingerich a calcule un nouveau modele en equilibre radiatif de Ia photosphere en tenant compte soigneusement de I' effet de blanketing (14): des ecarts notables et inexpliques subsistent avec les observations de Ia courbe d'energie solaire. Frisch (15) etudie !'influence des fortes raies de Fraunhofer sur l'equilibre radiatif dans les couches superieures ou il n'y a plus equilibre thermodynamique local. Cependant les contributions les plus importantes aux problemes de transfert dans Ia photosphere portent sur !'interpretation des fluctuations locales du rayonnement emergent. Wilson (3, 4) traite cette question en vue de !'interpretation des donnees sur la variation centre-bord des ecarts quadratiques moyens de brillance dans la granulation en termes de fluctuations de temperature. L'analyse du meme probleme par Edmonds (x6) conduit a des fluctuations thermiques qui croissent regulierement avec la profondeur et atteignent une valeur quadratique moyenne de 450° (a T constant) vers T = I ·3 ou 740° a profondeur geometrique constante. Dans un article plus recent (5) Wilson montre que les valeurs moyennes de Ia fonction-source S dans Ia photosphere deduites des valeurs moyennes de l'intensite emergente en appliquant !'equation de transfert de !'atmosphere homogene (negligeant Ia granulation) ne sont pas correctes, parce que les relations entre S et T, et surtout entre T et T, ne sont pas lineaires. Une analyse entierement coherente du spectre continu solaire compte tenu de ses fluctuations locales reste a faire. Des methodes mathematiques pour !'analyse du transfert de rayonnement dans un milieu fluctuant ont ete developpees par Rybicki (6). II etablit les equations qui lient les fluctuations

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d'opacite et d'energie locale (decrites par leurs fonctions de correlation) aux fluctuations du champ de rayonnement, en particulier du rayonnement emergent. La methode s'applique done au cas ou une partie de 1' energie n' est pas sous forme radiative. La theorie suggere que certaines fluctuations spatiales a grande echelle du rayonnement emergent sont liees a l'epaisseur de la couche convective plutot qu'a l'echelle adoptee pour la convection. De nouveaux efforts sont deployes pour obtenir une theorie hydrodynamique meilleure de la zone convective et on consultera avant tout dans ce domaine les mises au point de Spiegel et Bohm (RG 5). Dans un travail non encore publie Bohm a developpe une methode pour analyser les modes convectifs compte tenu de !'influence de la viscosite et de la conductivite thermique liees a la turbulence, ainsi que des echanges radiatifs; la methode permet une evaluation du spectre d'energie des modes convectifs. De nombreux travaux ont ete entrepris en vue d'expliquer les observations des oscillations photospheriques et d'analyser Ia propagation et la dissipation dans !'atmosphere solaire des divers modes possibles. Kato (7) a calcule le spectre du champ acoustique produit dans une zone de convection turbulente et modifie par son transfert dans 1' atmosphere stable. Le spectre obtenu a un pic au voisinage de la frequence critique. Par ailleurs le meme auteur a analyse la reponse d'une atmosphere stable a une perturbation ayant une source ponctuelle, perturbation harmonique (8) ou impulsive (9). Uchida (Io) a etudie la propagation des divers modes d'ondes gravitationnelles et aerodynamiques dans une atmosphere non isotherme et trouve que certains modes de periode 300 s sont pieges dans la couche voisine du minimum de temperature. II decrit d'autre part (u) !'excitation des oscillations par les mouvements des granules. Enfin Uchida etudie (12) Ia propagation dans la couronne de perturbations magneto-hydrodynamiques: !'intersection du front de l'onde rapide avec la surface solaire parcourt cette derniere a une vitesse de xo3 kms-1 et peut etre identifiee aux perturbations se propageant a partir des eruptions solaires (films de Moreton, Lockheed Solar Observatory). Souffrin (13) a etudie le 'filtrage' par une atmosphere convectivement stable du champ de vitesse aleatoire qui est impose a sa base par une couche convective sous-jacente. L'atmosphere se comporte comme un filtre coupant les basses frequences et le spectre des oscillations photospheriques peut etre explique comme consequence de ce filtrage. La dissipation radiative s'oppose a !'existence d'ondes de gravite dans la photosphere. Enfin Meyer et Schmidt (RG 10) ont analyse Ia reponse de !'atmosphere stable a I' excitation par un 'granule', considere comme un soulevement local de la couche limite inferieure. Pour un choix convenable des parametres decrivant ce granule, il y a excitation des modes d'oscillations propres de !'atmosphere; Ia solution numerique permet d'interpreter les oscillations observees. INSTRUMENTS

On notera avec satisfaction la multiplication des grands instruments solaires modernes. Dans l'ile de Capri le Fraunhofer Institut a installe un telescope d'une conception revolutionnaire dont on trouvera Ia description par Kiepenheuer et Mattig dans Ia reference (RG 10). Un magnetographe photoelectrique permettant de mesurer le vecteur champ magnetique lui est associe (Deubner, RG 10). A l'Observatoire Astrophysique de Crimee le magnetographe a ete adapte a la mesure des champs transverses (Bruns et al. (1)) ainsi qu'a la mesure des composantes longitudinales pour deux raies. Les memes facilites existent a l'IZMIRAN (Joschpa, Obridko (:z)). D'autre part le spectrometre a double passage pour Ia mesure des profits des raies de Fraunhofer a Poulkovo est decrit par Karpinsky (3).

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Livingston a etabli un remarquable magnetographe en association avec le telescope McMath de l'Observatoire de Kitt Peak. Deux raies peuvent etre mesurees simultanement; avec 5250 Fe I le bruit est seulement de o·5 gauss pour un trou d'exploration de I" x I" et une constante de temps de I s. L'appareil peut etre aussi adapte a Ia mesure des trois composantes du vecteur champ. A Kodaikanal egalement un magnetographe photoelectrique a ete construit par Battacharya. A Meudon un laboratoire de spectroscopie solaire a telescope horizontal (D = 40 em, F = IJ m) construit par G. Wlerick est entre en service en I965. Le meme auteur dirige la construction de Ia nouvelle tour solaire (D = 6o em, F = 45 m) qui pourra etre utilisee en 1967-68. Un nouveau coronometre photoelectrique ameliore, construit par P. Charvin, doit etre installe a l'Observatoire de Nice. Enfin a Sacramento Peak Ia nouvelle tour solaire sera Ia premiere a comporter un telescope dans le vide, ainsi que nombre de particularites revolutionnaires. Sa construction est activement poursuivie sous Ia direction de Dunn et Evans. Nous avons aussi ete informe de nouvelles realisations instrumentales pour !'etude du Soleil a Edinburgh (Briick), a Kanzelhohe (Mathias) et a Arosa ou un nouveau coronographe .a ete installe (Waldmeier). BIBLIOGRAPHIE

References Generales :t. :2.

3· 4· 5·

6. 7·

8. 9·

::to. :II.

I:Z.

The solar spectrum, Ed. C. de Jager, D. Reidel Publ. Co., Dordrecht, 1965. Stellar and solar magnetic fields, Ed. R. Liist, IAU Symposium no. 22, North Holland Publ. Co., Amsterdam, 1965. Astronomical observations from Space vehicles, Ed. J. L. Steinberg, IAU Symposium no. 23, in Ann. Astrophys., 27, 28; also in book from Publ. CNRS, Paris, 1965. Abundance determinations in stellar spectra, Ed. H. Hubenet, IAU Symposium no. 25, Acad. Press, London and New York, 1966. Cosmical gas dynamics, Ed. R.N. Thomas, IAU Symposium no. 28, Acad. Press, London and New York, 1967. Solar physics, Ed. J. Xanthakis, John Wiley and Sons Ltd., London, in press. First Harvard-Smithsonian Conference on stellar atmospheres, Cambridge, Mass., 1964, Smithson. Inst. astrophys. Obs., spec. Rep., no. 167, 1964. Second Harvard-Smithsonian Conference on stellar atmospheres, Cambridge, Mass., 1965, Smithson. Inst. astrophys. Obs., spec. Rep., no. 174, 1965. Campi magnetici solari e la spettroscopia ad alta risoluzione, Ed. M. Cimino, Barberi, Firenze, sous presse. The fine structure of the solar atmosphere, Ed. K. 0. Kiepenheuer, Forschungsberichte Deuts. Forschungsgemeins., F. Steiner Veri. Wiesbaden, 1966. Solar corona and corpuscular radiation in interplanetary space, S. K. Vsekhviatsky et al., Kiev University, 1965. Billings, D. E. A guide to the solar corona, Acad. Press, London, New York, 1966.

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COMMISSION 12 Makarova, E. A. I965, Astr. Zu., 42, 681. Makarova, E. A. I964, Astr. Zu., 4I, 288. Lambert, D. L., Willstrop, R. V. I965, Observatory, 85, I24. Houtgast, J. I965, Koninkl. Nederl. Akad. Wetensch., Amsterdam Proceed., Series B, 68, no. S· Murcray, F. H., Murcray, D. G., Williams, W. J. I964, Appl. Opt., 3, I373· Beer, R. I966, Nature, 209, no. 5029, I226. Lena, P. I966, Ann. Astrophys., 29, 361. Noyes, R., Gingerich, 0., Goldberg, L. I966, Astrophys. J., I45o 344· Blamont, S., Bonnet, R. I966, C.R. Acad. Sci., Paris, 262, 3I52. Kodaira, K. I965, Z. Astrophys., 6o, 240. Mouradian, Z. I965, Ann. Astrophys., 28, 8os. Kristenson, H. I964, Mon. Not. R. astr. Soc., 128, I3. Heintze, J. R. W. I965, Rech. astr. Obs. Utrecht, I7. Mulders, G. F. W., Slaughter, C. D. I965, Publ. astr. Soc. Pacif., 77, 295· Appenzeller, 1., Schroter, E. H. Astrophys. J., sous presse. Cowley, C. I965, Astr. J., 70, 671. Delache, Ph. Astrophys. J., (soumis a). Delache, Ph. I966, Ann. Astrophys., 29, I09. I965, Veroff. Inst. Theoret. Phys. Sternw., Kiel. Bode, G.

Atlas et Tables du Spectre de Fraunhofer. Identifications I. Ahmad Kiasatpoor I962, Georgetown Obs. Monograph, no. I9. 2. Swensson, J. W., Risberg, G. I966, Ark. Fys., 3I, no. I6. I966, Z. Astrophys., 64, II. 3· Swensson, J. W. 3 his. Swensson, J. W. Bull. Acad. Roy. Belg, (sous presse.) 4· Grevesse, N. I966, Ann. Astrophys., 29, 365. I964, Z. Astrophys., 6o, 24. 5· Kodaira, K. I965, Ann. Astrophys., 28, 703. 6. Swings, J. P. 7• Swings, J.P. I966, Ann. Astrophys., 29, 371. I965, Astrophys. J., I4I, u26. 8. Mitchell, W. E., Jr., Mohler, 0. C. 9· Swensson, J. W. I96o, Ark. Fys., 32, no. 25, 463. 10. Pottasch, S. R. I964, Space Sci. Rev., 3, 8I6. u:, Goldberg, L., Parkinson, W. H., Reeves, E. M. I965, Astrophys. J., 14I, I293· I2. Black, W. S., Booker, D., Burton, W. M., Jones, B. B., Shenton, D. B., Wilson, R. Nature, 206, no. 4985, 654. I3. Burton, W. M., Wilson, R. I965, Nature, 207, no. 4992, 61.

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Aslanov, I. A. I963, Astr. Zu., 40, Io36. Aslanov, I. A. I964, Uchen. Zap. Leningrad. gos. Univ., Ser. mat. Nauk, :n, no. 38, 53· I964, Acad. Sci. Az. SSR, Bakou. Aslanov, I. A. Melnikov, 0. A., Zhuravlev, S. S., Aslanov, I. A., Kuliev, D. M., Salmanzade, R. Kh. I964, Trans. Shamakha astr. Obs., 3, 63. Melnikov, 0. A., Zhuravlev, S. S., Aslanov, I. A., Kuliev, D. M., Salmanzade, R. Kh. I964, Uchen. Zap. Leningrad. gos. Univ., Ser. mat. Nauk, 2I, no. 38, 27. I964, Izv. glav. astr. Obs. Pulkove, 23, no. I75· Melnikov, 0. A. Ward, F. I964, Astr. J., 69, 562. w.lrd, F. I964, Pure appl. Geophys., s8, I 57· Ward, F. I965, Astrophys. J., I4I, 534· Starr, V. F., Gilman, P. A. I965, Astrophys. J., I4I, I I 19. Starr, V. P., Gilman, P. A. 1965, Tellus, I7, 334· Sakurai, T. 1966, Pub!. astr. Soc. Japan, I8, 174. Rubashev, B. M. I965, Izv. glav. astr. Obs. Pulkove, 24, no. 178, 41.

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La Photosphere (a) Granulation. Structures cinematiques et magnetiques I. Bray, R. J., Loughhead, R. E. The solar granulation, International Astrophysics Series, Chapman and Hall, London (in press). 2. Vassiljeva, G. Y., Yudina, I. V. 1965, Soln. Dann., no. 3, 58. 3· Krat, V. A., Petrova, N. N. 1965, Soln. Dann., no. 10, 48. Ann. Astrophys. (soumis aux). 4· Levy, M. 5· Edmonds, F. N., Jr., McCullough, J, R. 1966, Astrophys.J., I44, 754· 6. Simon, G. W., Leighton, R. B. 1964, Astrophys. J., 140, II20. 7· Levy, M. 1965, C. R. Acad. Sci., Paris, 260, 8o6. 1965, Ann. Astrophys., 28, 534· 8. Edmonds, F. N., Jr., Michard, R., Servajean, R. 9· Mein, P. 1966, Ann. Astrophys., 29, 153. IO. Edmonds, F. N., Jr. 1966, Astrophys. J., I44, 733· II, Edmonds, F. N., Jr. 1967, Solar Physics, I, 5. I2. Orrall, F. Q. 1965, Astrophys. J., J4I, II3I. I3. Orrall, F. Q. 1966, Astrophys. J., I43, 917. 14. Vasiljeva, G. Y. 1964, Izv. glavn. astr. Obs. Pulkove, 23, no. 175, 28. 1965, Izv. glavn. astr. Obs. Pulkove, 24, no. 178, 26. IS. Krat, V. A., Vjalshin, G. F. Boulder AAS Meeting, October, 1966. 16. Beckers, J. M., Schroter, E. H. 17. Severny, A. 1965, Astr. Zu., 42, 217. 1966, Izv. Krym. astrofiz. Obs., 3S· 18. Severny, A. I9. Severny, A. 1966, Izv. Krym. astrofiz. Obs., 37 (in press). 20. Livingston, W. C. 1966, Scientific American, 2I5, no. 5, 54· 2I. Grigorjev, V. M., Stepanov, V. E. 1966, Reports on Solar Physics, Sib. IZMIR. Acad. Sci. USSR, 32. 1966, Observatory, 86, 73· 22. Stenflo, J. 0. 23. Michard, R. 1964, Trans. IAU, 12B, 532. 24. Pikelner, S. B. 1966, Usp. fiz. Nauk, 88, 505. 25. Severny, A. 1966, Usp. fiz. Nauk, 88, 3· 26. Bumba, V., Howard, R., Smith, S. F. Proc. Goddard Magnetic Stars Symposium, 1965, in press.

(b) Profits et largeurs equivalentes des raies de Fraunhofer De Jager, C., Neven, L. Bull. astr. Inst. Nether[. (sous presse). De Jager, C., Namba, 0., Neven, L. 1966, Bull. astr. Inst. Nether[., I8, 128. De Jager, C., Neven, L. 1966, Bull. astr. Inst. Nether!., I8, 306. De Jager, C., Neven, L. 1964, Mem. Soc. R. Sci. Liege, 9, 151. De Jager, C., Neven, L. 1967, Solar Physics., I, 27. Kulander, J. L., Jefferies, J. T. 1966, Astrophys. J., I46, 194. 1964, Astr. Zu., 4I, 920. Kuli-Zade, D. M. 1965, Astr. Zu., 42, 1022. Kuli-Zade, D. M. Kuli-Zade, D. M. 1964, Vestnik Leningrad Univ., no. 19. Kuli-Zade, D. M. 1964, Soln. Dann., no. II, s6. II. Khetsuriani, T. S. 1965, Acad. Sci. Georg. SSR, 37, no. 3, 563. 1965, Z. Astrophys., 62, 83. 12. Bubke, 0. 13. Foppl, H. et al. 1964, Max Planck Inst. Phys. Astrophys. Miinchen, MPI-PA-23/64. 14· Cowley, C. R., Cowley, A. P. 1964, Astrophys. J., I40, 713. IS. Nissen, P. E. 1965, Ann. Astrophys., 28, ss6. 16. Schadee, A. 1964, Bull. astr. Inst. Nether!., I7, 311. I7. Ruzickova-Topolova, B. 1965, Bull. astr. Inst. Csl., 16, 23. 18. Withbroe, G. L. Astrophys. J. (sous presse). 1964, Z. Astrophys., 6o, 199. I9. Poletto, G., Rigutti, M. 20. Olson, E. C. 1966, Astrophys. J., I43, 904. I. 2. 3· 4· 5· 6. 7· 8. 9· IO.

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(c) Theorie du spectre de Fraunhofer I, 2. 3· 4· 5· 6. 7• 8. 9· IO, II.

12. I3. 14. IS. x6. I7. IS. I9.

1965, Ann. Astrophys., 27, 695. Johnson, H. R. Ann. Astrophys., 1966 (sous presse). Chamaraux, P. 1966, Ann. Astrophys., 29, 271. Henoux, J.-C. 1966, C.R. Acad. Sci., Paris, 263, 85. Dumont, S. 1966, C.R. Acad. Sci., Paris, 262, 740. Dumont, S. 1964, C.R. Acad. Sci., Paris, 258, 3292. Cuny, Y. Z. Astrophys. (sous presse). Holweger, H. 1964, Astr. Zu., 4I, 907. Teplitskaya, R. B. 1963, Astr. Zu., 40, 427. Mitropolskaya, 0. N. 1964, Astr. Zu., 4I, 930. Mitropolskaya, 0. N. 1966, Astr. Zu., 43, 694. Mitropolskaya, 0. N. 1965, Astr. Zu., 42, 1250. Pande, M. Ch., Sitnik, G. F. 1966, Astr. Zu., 43, 407. Pande, M. Ch. 1966, Astr. Zu., 43, 708. Pande, M. Ch. 1963, Izv. Krym. astrofiz. Obs., 30, 267. Rachkovsky, D. N. 1965, lzv. Krym. astrofiz. Obs., 33, III. Rackhovsky, D. N. 1964, Z. Astrophys., 59, 66. Gussman, E. A. Z. Astrophys. (sous presse). Gussman, E. A. 1964, Z. Astrophys., 6o, 167. Traving, G.

(d) Abondances des elements I. 2. 3· 4· 5· 6. 7· 8. 9· IO, II,

I2. I3. I4. IS. I6.

1964, Astrophys. J., 140, 707. Goldberg, L., Kopp, R. A., Dupree, A. K. 1965, Bull. astr. Inst. Csl., I6, 3II. Leftus, V. 1965, Publ. astr. lnst. Csl., no. 51, 17. Leftus, V. 1964, Appl. Optics, 3, 467. Mitchell, W. E., Mohler, 0. C. 1964, Proc. nat. Acad. Sci., 51, 1238. Aller, L. H., O'Mara, B. J., Little, S. 1965, Adv. Astr. Astrophys., 3, I. Aller, L. H. 1966, Mon. Not. R. astr. Soc., 132, 87. Mugglestone, D., O'Mara, B. J. 1966, Astrophys. J., I44, 376. Chapman, R. D., Clarke, W. H., Aller, L. H. 1966, Ann. Astrophys., 29, 379· Righini, A., Rigutti, M. 1966, Icarus, 5, 75· Wallerstein, G. 1966, Ann. Astrophys., 29, 287. Grevesse, N. 1965, Astrophys. j., I42, 396. Lynds, C. R. 1964, Izv. Krym. astrofiz. Obs., 32, 26. Dubov, E. E. 1965, Z. Astrophys., 62, 143. Schmahl, G., Schroter, E. H. 1964, Ann. Astrophys., 27, 417. Gokdogan, N., Peeker, J.-C. Astrophys. J. (sous presse). Herzberg, L., Delbouille, L., Roland, G.

(e) Modeles et theories de Ia photosphere et de Ia zone convective I. 2. 3· 4· 5· 6. 7· 8. 9· IO, II.

I2. I3, I4, IS. I6.

1964, Bull. astr. Inst. Nether!., I70 442. Heintze, J. R. W., Hubenet, H., De Jager, C. 1965, Astrophys. J., I42, 326. Waddell, J. 1964, Astrophys. J., I39, 929. Wilson, P. R. 1964, Astrophys. J., I40, II48. Wilson, P. R. 1965, Astrophys. J., I42, II95· Wilson, P. R. 1965, Smithson. lnst. astrophys. Obs., spec. Rep., no. 180. Rybicki, G. B. 1966, Astrophys. J., I43, 372. Kato, S. 1966, Astrophys. J., I43, 893. Kato, S. 1966, Astrophys. J., I44, 326. Kato, S. 1966, Astrophys. J., I42, 335· Uchida, Y. 1967, Astrophys. j., I47, (sous presse). Uchida, Y. (sous presse, revue non precisee). Uchida, Y. 1966, Ann. Astrophys., 29, 55· Souffrin, P. 1966, J, quant. Spect. rad. Transfer, 6, 609. Gingerich, 0. 1966, J. quant. Spect. rad. Transfer, 6, 629. Frisch, H. 1966, Astrophys. J., I44, 733· Edmonds, F. N. Jr.

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Instruments

1965, lzv. Krym. astrofiz. Obs., 23, So. Bruns, A. V., Nikulin, N. S., Sevemy, A. B. 1965, in Regul. issled. Progr. mejd. geofiz. God., Soln. Joschpa, B. A., Obridko, V. N. Aktiv., p. 131, Ed. Izdatel. Nauka, Moscou. 1965, Izv. glav. astr. Obs. Pulkove, 24, no. 178, 84. 3· Karpinsky, V. N. I,

2.

THE CHROMOSPHERE

Report prepared by R. G. Athay (a) Trends in Research and Reviews

The period since the previous Draft Report seems to be characterized by somewhat more emphasis on disk observations of chromospheric structure and chromospheric heating and somewhat less emphasis on eclipse data. However, new spectrophotometric data from eclipses still plays a vital role in chromospheric research. Much important data from earlier eclipses still remain unpublished. Eclipse observers are urged to make data available to other astronomers on a shorter time scale than has been characteristic of the past. Review articles on chromospheric phenomena by J. T. Jefferies, R. G. Athay, H. E. Hinteregger and R. 0. Redman are contained in the proceedings of the Utrecht Conference on The Solar Spectrum (1) held in 1963. Other important reviews include a review of the extreme ultra-violet spectrum of the chromosphere by Tousey (2). (b) Spectrophotometry at Eclipse

Optical continuum intensities near the solar limb recorded at the 1954 total eclipse have been reported at four wavelengths, ..\A 386o, 4155, 4760 and 6190, by Kristensen (1) and at five wavelengths, .:u 4605,4910, 5200, 5700 and 6430, by Heintze (2). Narrow band continuum intensities in the blue and red regions of the spectrum were measured at the 1961 eclipse by Mouradian (3). All of these data are in fair quantitative agreement with each other and with earlier continuum data. The continuum data now provide a rather good basis for realistic models of the lower chromosphere. However, improved photometric precision is still needed. Radio continuum brightness temperatures at 3 em were observed at the 1961 eclipse by Hackenberg, Popowa and Prinzler (4) and by Drago, Noci and Piatelli (5). The latter authors report limb brightening along equatorial diameters and limb darkening along polar diameters, a result that may be due partially to coronal contributions but may also have a strong chromospheric component. Makita (6) has reported intensities and profiles of Hex and the H and K lines observed at the 1958 eclipse and intensities of Hf3, Hy, HS and H and K observed at the 1961 eclipse have been reported by Stolov (7). Takayanagi (8) has reported intensities in the CN ..\ 38oo band observed at the 1958 eclipse. Successful observations at the May 1965 eclipse were made by Houtgast (9) and several groups have reported successful observations at the 1966 May 20 and November eclipses. Data for these more recent eclipses are not yet available. (c) Spectrophotometry of the Disk and at the Solar Limb Outside of Eclipse

Observers at the Kitt Peak Observatory under the supervision of Pierce (1) are preparing a catalogue of approximately 8ooo emission lines observed in the low chromosphere at the solar limb with the McMath tower telescope. We look forward to the publication of this important catalogue in the near future.

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Mouradian (cf. ref. 3 §b) and Guljaev (10) have observed the profiles of the Paschen-gamma and .\ 10 830 lines for the mean (spicules unresolved) chromosphere. Profiles and equivalent widths are given as a function of height. White and Wilson (2) report similar data for Hoc and conclude that unit opacity at line center is found at about 1500 km above the solar limb. Considerable discussion of the phenomena of a 'double-limb' observed in Hoc filtergrams occurred during this period. Both Bhavilai, Norton and Giovanelli (3) and Simon and White {4) report that the 'double-limb' effect disappears when proper allowances and corrections are made for scattered light in the optical system. Disk profiles of the .\ IO 830 line were observed by de Jager, Namba and Neveu (5). They conclude that this line is formed predominately in spicules covering about 10% of the solar disk, that the optical thickness of spicules at line center is I ·3 to 2 ·6 and that the mean broadening velocity is 9-u km s-1 • Fisher (6) finds for the same line r 0 = 2 to 4 and a broadening velocity of IS km s-1 has published a profile of the mean Hoc line on the disk with a central intensity of IS·s%. Zirin and Howard (7) show from spectroheliograms made at .\ IO 830 that IO 830 absorption is limited to the edges of the chromospheric network. They interpret this to mean that the network boundaries have relatively high temperature and density. Suemoto (8) has studied variations in the H and K profiles observed with high resolution from point to point on the solar disk. He interprets the profile as a superposition of emission and absorption lines. White (9) has published data on the mean Hoc profile on the disk showing a central intensity of IS·S%· Measurements of chromospheric polarization in Hoc by Bruckner (RG 9) give information on polar magnetic fields. (d) Spectrophotometry in the XUV Tousey's (ref. 2, §a) review article includes profiles of the Mg II resonance lines, showing the central emission features well resolved but with insufficient quantitative information. Profiles of Lyman-oc and Lyman-,8 lines observed at different positions on the disk are given by Tousey, Purcell, Austin, Garrett and Widing (x). The wavelength interval from.\,\ 3Io-55A 1"41-')· In the spectra of satellites I and IV these peculiarities are absent (3, 52, 53). U. V. Alexandrov (Kharkov Astronomical Observatory) analysed theoretically data received by the Kharkov Astronomical Observatory in 1933-58 concerning brightness distribution across the Jovian disk for one-layer and two-layer models of atmosphere and determined the values of the optic parameters (54). At the Main Astronomical Observatory (Pulkovo), inner radiation belts of Jupiter were discovered (55) by goniometrical observations on the wavelength 6·4 em. It was shown that the presence of gyrotropic atmosphere or phase temperature effect leads to some polarization of the planet's integral radio-emission (56). A. A. Kaliniak discovered indications of non-stable atmosphere around three Galilean satellites of Jupiter (57). S. K. Vsekhsviatskij (Kiev State University)' noticed an unusual activity of Jupiter in 1962-65 and explained it as a display of volcanic activities (58, 59, 6o, 61). At the Crimean Astrophysical Observatory considerable intensity fluctuations of the ultraviolet spectral region for equatorial and polar sections of the Jovian disk connected with periods of greater activity in its atmosphere were discovered (62). At the Abastumani Astrophysical Observatory electropolarimetric investigations of the surfaces of Jupiter and Saturn were carried out in the focus of the 40 em refractor. Polarization of the planet's integral light is low (from o·I% to o·s%) and does not show any evident dependence on the phase angle. Polarization in the central and polar regions is comparatively high and it depends on the phase angle. For all this, for both planets, the southern regions show greater polarization than the northern ones (maximum degree of polarization of the southern region of Jupiter is equal to 9·4%, and of Saturn 11•7%). Especially high polarization (up to 14-15%) is displayed by the east and west sides of the outer ring of Saturn, and in this respect the west side always dominates over the east side (63). At the Gorky Scientific Research Institute (NIRFI) brightness temperatures of Jupiter and Saturn near 1·25 em region (ammonia resonance) were estimated. The difference between the brightness temperature and the infra-red temperature of the cloud layer for Jupiter and Saturn makes up sooK (64). Plasma frequency concerning the origin of decametrical radio-emission of Jupiter, with allowance to the planet's magnetic field, was discussed. The presence of characteristics of decametric emission may be explained if the magnetic field in the planet ionosphere amount to some oersteds and the electron concentration is 3·1o 5 electrons cm-3 • In particular, this value of concentration is enough to explain direction of emission owing to gyroresonance absorption (65, 67, 68). The movement of ionized gas in Saturn's exosphere under the influence of a force due to its rings, which is perpendicular to the magnetic field, was considered. The character of plasma drain due to the rings, and the magnetic field distortion in case of fully or slightly ionized gas was investigated in detail. The received criteria of considerable distortion of force lines allow (when there are experimental data of orientation of the polarization plane of radio-emission of Saturn) to judge over physical conditions in the planet's exosphere as well as over possibilities of existence of Saturn's radiation belts (66). In September and October 1963 in the U.S.S.R., Jupiter's radio-location on the frequency 700 MHz was carried out. Average reflection factor of Jupiter is equal to 10% (~).

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On the basis of photometric data analysis M.S. Bobrov (Astronomical Council of the U.S.S.R. Academy of Sciences) showed that Saturn's rings present a system with thickness of many particles. Divergences in observing the phase curve and the theory of 'inter-darkening' are explained by the fact that in the inter-darkening theory dispersion of particle sizes was not taken into account; and taking this fact into account leads to a good agreement between theory and observations. It was shown that neither diffraction of separate particles nor the opposition effect of Hapke and Gerels can explain the observing factors. Problems of ring dynamics were considered (70). M. S. Bobrov gave an account of a number of rare phenomena in the Saturnian system, which will take place in I966 and worked out a programme for their world-wide patrol observations (71). According to his proposal, IAU Commission I6 circulated proposals dealing with observations of Saturn at the time of the Earth's and Sun's passage across their plane and with observing the non-illuminated side of the rings. V. I. Moroz identified with CH 4 the strong absorption bands in Saturn's spectrum in the region of I-2'5/L· In spectra of rings obtained with the 2·6 m reflector at a highly satisfactory signal to noise ratio details typical to reflection from icy particles are very distinctly seen (3,

51, 72).

Saturn's brightness temperature measured at FIAN of the U.S.S.R. averaged only over its disk, equals I32 ± 9°K, what is very close to the value received by the measurements in the infra-red region. Allowance for the radio-emission of the ring allows, according to M. S. Bobrov, to adjust the received value with the latest data of measurement in the region of 8-14p. (73)·

' Laboratory and Theoretical Research. Cosmogonical Problems In the astrophysical laboratory of Pulkovo Observatory a 97 metre tube has been installed and tested; its purpose is investigation of molecular spectra of gas absorption. Changes in equivalent width of oxygen absorption lines (Band A) were studied depending on pressure change in the range from o· I to I atm for single and triple of passage light through the tube. (Mitrofanova, L. A., Jukova, L. N., Derviz, T. E.) (74). U. V. Alexandrov and V. I. Garaja (Kharkov Astronomical Observatory) made a calculation of polydispersive indicatrices of light dispersion on particles, electrical properties of which differ slightly from the properties of surrounding medium (75). E. G. Janovitskij (Kiev, Golosejevo) received approximate solution of a problem on diffuse reflection and light transmission through planets' atmospheres when dispersion indicatrix is arbitrary (but not very much oblate) (76). V. V. Sobolev (Astronomical Observatory of the Leningrad State University) obtained average optical characteristics of the atmosphere of Venus (dispersion indicatrix, albedo of single dispersion). Meanwhile a modern theory of light dispersion and new observations data about changes in the stellar magnitude of Venus with phase were employed (77). Some works by V. V. Sobolev and I. N. Minin(78-81)are devoted to theoretical investigation of light dispersion in the planet's atmosphere with regard to atmosphere layers' curvature. In the paper (78) integral and in (79) approximate differential equations of the problem are considered. These equations are solved approximately by the method of averaging by angles for homogeneous (So) and inhomogeneous (81) atmospheres. The obtained results can be applied to problems connected with studying twilight phenomena and planets' luminescence near terminator. I. N. Minin offered an approximate method of solving the problem of polarized iight

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dispersion in planet's atmosphere taking into account aerosol component and light reflexion from the surface (82). B. Ju. Levin (Institute of Physics of the Earth) made a review of works dealing with the study of the formation process of planets. He also treated the problem of changing the content of metallic iron of primary and secondary origin in planets depending on the distance towards the Sun (84). V. S. Safro~ov (Institute of Physics of the Earth) made a critical review of modern hypotheses on the origin of the protoplanetary cloud (85). The problem of the origin of asteroids and dispersion of their speeds was studied (86) as well as the origin of thermal inhomogeneities in the primary Earth connected with the dropping of large bodies into it during its formation (87). From the inclinations of the planets' rotation axes it was discovered that the masses of the largest bodies fallen on planets were of the order of a thousandth of their mass (88). E. L. Ruskol (Institute of Physics of the Earth) considered the problem of dissipation of a considerable part of lunar tidal energy in the layer of reduced viscosity in the depth of 1oo300 km (89)· S. V. Kozlovskaja (Institute of Physics of the Earth) tabulated the most probable mass values and radii of planets and satellites (90). From the comparative analysis of the inner structure of the planets' of the terrestrial group, it was found out that the substance of Mars and Venus on the whole is slightly denser than the substance of the Earth (91). S. V. Majeva (Institute of Physics of the Earth) investigated the possibility of heating-up bodies of asteroid sizes by long-lived radioactive elements (92). She constructed curves of temperature distribution by depth for equal time moments for Mars and the Moon (93). BIBLIOGRAPHY

Mercury 1963, 'C0 2 in Atmosphere of Mercury', Astr. Cirk., Moscow, no. 270. I. Moroz, V. I. 1964, 'Infra-Red Spectrum of Mercury(,\ I'0-3'9/L)'. Astr. Zu., 41, no. 6, 2. Moroz, V. I. 1108. 3· Moroz, V. I. 1965, 'Infra-Red Spectra of Planets, Stars and Nebulae', Thesis, Moscow State University. 4· Kutuza, B. G., Losovskiy, B. ]., Salomonovitch, A. E. 1965, 'Measurements of RadioEmission of Mercury on 8-mm Wave', Astr. Cirk., Moscow, no. 327, 5· Venus 5· Polojentseva, G. A. 1964, 'About Violet Absorption in Spectrum of Venus', Izv. glav. astr. Obs. Pulkove, 23, no. 175, 75· 6. Kozyrev, N. A. 1966, Izv. glav. astr. Obs. Pulkove, 24, no. 180. 7· Barabashov, N. P. 1965, 'About Photometric Peculiarities of Light Reflection from the Visible Surface of Venus', Vestnik Karkovsk. gos. Univ., no. 4, Ser. Astr., no. 1, 13. 1965, 'Spectrophotometric Investigations of the Great 8. Barabashov, N. P., Belkina, I. L. Dark Spot on Venus', Vestnik Karkovsk. gos. Univ., no. 8, Ser. Astr., no. 2, 3· 9· Barabashov, N. P. 1966, 'Spectrophotometry of the Great Dark Spot on Venus', Astr. Cirk., Moscow, no. 353· 10. Jevsjukov, N. N., Jezersky, V. I. 1965, 'About Optic Properties of the Atmosphere of Venus', Vestnik Karkovsk. gos. Univ., no. 4, Ser. Astr., no. 1, 71. 11. Moroz, V. I. 1964, 'Recent Observations of Infra-Red Spectra of Planets (Venus 1-4p., Mars I-4p. and Jupiter I-6p.)', Mem. Soc. R. Sci. Liege, 5eme serie, 9. 520. 12. Moro?:, V. I. 1964, 'Infra-Red Spectra and the Problem of Physical Conditions on the Surface of Venus'. Proceedings of the XIII-th International Astronautical Congress, Varna, 1962, Springer Verlag, Wien and New York. IJ. Jesipov, V. F., Moroz, V. I. 1963, 'Experiment of Spectrophotometry of Venus and Mars in the Interval of 7ooo-Io oooA', Astr. Cirk., Moscow, no. 262, 1.

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I4. Moroz, V. I. 1963, 'New Observations of Infra-Red Spectrum of Venus', Astr. Cirk., Moscow, no. 262, 6. IS· Moroz, V. I. 1964, 'New Observations of Infra-Red Spectrum of Venus (.\I ·2-3"8/L)', Astr. Zu., 4I, 71 I. I6. Moroz, V. I. 'Bands C0 2 and Some Optic Properties of Atmosphere of Venus', Astr. Zu. (in press). I7. Moroz, V. I. 1964, 'Phase Effect of Intensified Absorption Bands C0 2 in Spectrum of Venus', Astr. Cirk., Moscow, no. 305. IS. Vetuhnovskaja, U.N., Kuzmin, A. D., Kutuza, B. G., Losovskij, B. J., Salomonovitch, A. E. 1963, 'Measurements of Radio-Emission Spectrum of Venus Night Part in centimeter Wave Range'. Izv. Vyssih Uceb. Zaved. Radiofiz., 6, 1054. I9· Troitskiy, V. S. 1964, 'To the Theory of Radio-Emission of Venus and Mars'. Izv. Vyssih Uceb. Zaved. Radiofiz., 7, 202. 1964, 'About Venus Model with "Cold" Absorbing Atmosphere'. 20. Kuzmin, A. D. Izv. Vyssih Uceb. Zaved. Radiofiz., 7, 1021. 2I. Basharinov, A. E., Vetuhnovskaja, U. N., Kuzmin, A. D., Kutuza, B. G., Salomonovitch, A. E. 1964, 'Measurements of Brightness Temperature of the Illuminated Part of Venus on 8 mm Wave'. Astr. Zu., 4I, 707. 1965, 'To the Theory of Radio-Emission of Venus'. Izv. Vyssih Uceb. 22. Kuzmin, A. D. Zaved. Radiofiz., 8, 7· 23. Kuzmin, A. D., Clark, B. G. 'Measurements of Polarization and Distribution of Brightness Temperatures of Venus on 1o·6-cm wave'. Dokl. Akad. Nauk SSSR, I6I, 551, 1965; Astr. Zu., 42, 595, 1965; Astrophys. J., I42, 23, 1965. 24. Kuzmin, A. D. 1965, 'Measurements of Brightness Temperature of the Illuminated Part of Venus on 10·6-cm Wave'. Astr. Zu., 42, 1281. 1965, 'Determination of Parameters of Dielectric 25. Basharinov, A. E., Kutuza, B. G. Constant of Water Drops in Cloud Formations According to Data of Radio-Astronomical Observations in Medium Wave Range'. Report at the sth All Union Conference on Radioastronomy. Kharkov, October. 1965, 'Fluctuation 26. Ananov, N. 1., Basharinov, A. E., Kirdjashev, K. P., Kutuza, B. G. of Radio-Emission of Cloud Atmosphere in the Millimeter Wave Range'. Radio-Engineering and Electronic Physics, IO, no. II, 1941. 27. Basharinov, A. E., Kutuza, B. G. 1965, 'About the Origin of Cloud Layer of Venus (according to the results, of radio-astronomical observations)'. Report at the International Symposium on Research of Planets' Surfaces and Atmospheres by RadioAstronomical Method. Puerto Rico, May. 28. Kotelnikov, V. A., et al. 1965, 'Radio-Location Observations of Venus in the Soviet Union in 1964'. Reports Dokl. Akad. Nauk SSSR, I63, so. 29. Prokofijev, V. K. 1966, 'About Presence of Oxygen in Atmosphere of Venus'. Izv. Krym. astrofiz. Obs., 34, 243, 1965; 36 (in press).

Mars 30. Morojenko, A. V. 1964, 'Results of Polarimetric Observations of Mars in 1962-63'. Collection 'Physics of the Moon and Planets'. Publishing House 'Naukova Dumka', Kiev, p. 58. 3I. Morojenko, A. V. 1960, 'Polarization Properties of Atmosphere and Surface of Mars'. Collection 'Physics of the Moon and Planets', Publishing House 'Naukova Dumka', Kiev. 32. Morojenko, A. V. 1966, 'Investigation of Polarization Properties of Light, Reflected by Different Samples of Earth Bed-Rocks'. Collection 'Physics of the Moon and Planets'. Publishing House 'Naukova Dumka', Kiev. 33· Koval, I. K. 1964, 'Photoelectric Measurements of Brightness Distribution Across Disk of Mars'. Life Sciences and Space Research, 7, 246. 34· Janovitskij, E. G. 1965, 'About Aerosol Component at Atmosphere of Mars'. Collection 'Astrophysical Problems', Publishing House 'Naukova Dumka'. 35· Moroz, V. I. 1963, 'Observation of Infra-Red Spectrum of Mars in the Interval of I"I-4"If£'· Astr. Cirk., Moscow, no. 262, 4·

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1963, 'Estimation of Carbon Dioxide Gas Content and Total Pressure 36. Moroz, V. I. According to Infra-Red Spectra of Venus and Mars', Astr. Cirk., Moscow, no. 273. 1964, 'Infra~Red Spectrum of Mars(>. I'I-4'IJ£)'. Astr. Zu., 41, 350. 37· Moroz, V. I. as. Vasiltchenko, N. v., Moroz, v. I. 'Spectrum of Mars in the Region of 1'1-2'51' (opposition of 1965)', Astr. Zu. (in press). 1964, 'Spectral Indications of the Presence of Snow in the Atmosphere 39• Kozirev, N. A. of Mars'. Information. Izv. glav. astr. Obs. Pulkove, 23, no. 175, 72. 1965, 'Observations of Radio40. Kutuza, B. G., Losovskij, G. J., Salomonovitch, A. E. Emission of Mars on 8-mm Wave'. Astr. Zu., (in press), 1963, 'Radio-Location of the Planet of Mars in the Soviet 41. Kotelnikov, V. A., et al. Union'. Dokl. Akad. Nauk SSSR, 151, 8n.

Jupiter and Saturn 1964, 'About Latitudinal Distribution of Methane Absorption Across 42· Tejfel, V. G. Disk of Jupiter'. Astr. Cirk., Moscow, no. 296. 1966, 'Molecular Absorption of Light in Atmosphere of Jupiter and 43· Tejfel, V. G. Surface Structure of the Planet Cloud Layer'. Collection 'Research of the Planet of Jupiter', Academy of Sciences of the U.S.S.R. 1966, 'Spectrophotometry of Methane Absorption Bands on Disk of 4+ Tejfel, V. G. Jupiter in the Near Infra-Red Region (o·7-I'OJ£)'. Astr. Zu., 43, 154. 'Comparison of Distribution of Methane Absorption of Disk of Jupiter 45· Tejfel, V. G. and Saturn'. Works of the Astrophysical Institute of the Academy of Sciences of the Kazakh SSR (in press). 'Distribution of Molecular Absorption of Methane across Disk of Jupiter 46. Tejfel, V. G. in the Near Infra-Red Region (o·7-I'OJ£)'. Works of the Astrophysical Institute of the Academy of Sciences of the Kazakh SSR (in press). 1964, 'To the Problem of Photometric Properties of the Red Spot on 47· Tejfel, V. G. Jupiter', Astr. Zu., 43, 531 . 'Preliminary Results of Spectrophotometry of the Red Spot on Jupiter'. .oJS. Tejfel, V. G. Works of the Astrophysical Institute of the Academy of Sciences of the Kazakh SSR, (in press). 1964, 'About Value of Temperature Gradient in beyond Cloud Layer of 49· Tejfel, V. G. Atmosphere of Jupiter'. Astr. Cirk., Moscow, no. 298. so. Pribojeva, N. V. 'Continuous Spectra of Satellites of Jupiter'. Works of the Astrophysical Institute of the Academy of Sciences of the Kazakh SSR (in press). 'Spectra of Jupiter and Saturn in the Region of I--2'51''. Astr. Zu. (in press). 51. Moroz, V. I. 1964, 'Infra-Red Spectra of lo and Ganimed. (o·?-z·sp.)'. Astr. Cirk., s:z. Moroz, V. I. Moscow, no. 297, I. J965, 'Experience of Infra-Red Spectrophotometry of Satellites; the Moon 53· Moroz, V. I. and Galileum Satellites of Jupiter', Astr. Zu., 42, 1287. 1965, 'Results of Surface Photometry of Jupiter', Vestnik Karkovsk. 54· Alexandrov, U. V. gos. Univ., no. 8, Ser. Astr., no. 2, 32. 1964, Astr. Cirk., Moscow, no. 283. 55· Korolkov, D. V., Parijskij, U.N., Timofejeva, G. M. 1964, Astr. Zu., 41, 362. 56. Soboleva, N. S., Parijskij, U. N. 1965, 'Data on Galileum Satellites of Jupiter'. Astr. Zu., 42, 1067. 57· Kaliniak, A. A. 1965, 'Processes in the System of Jupiter'. Astr. Cirk., Moscow, 58. Vsekhsviatskij, S. K. no. 317. 1965, 'About Nature of Changes on the Surface of Jupiter'. Astr. 59· Vsekhsviatskij, S. K. Zu., 42, 639. 1965, 'Changes on Jupiter'. Information Bulletin 'Geophysics and 6o. Vsekhsviatskij, S. K. Astronomy', Kiev, no. 8, 3· 'Results of Observations of Jupiter in 1962-65'. Works of the 61. Vsekhsviatskij, S. K. Astrophysical Institute of the Academy of Sciences of the Kazakh SSR (in press). 1964, 'About Some Properties of Atmosphere of Jupiter'. Izv. Krym. 6:z. Galkin, L. S. astrofiz. Obs., 32, II; 35 (in press).

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63. Bolkvadze, 0. R. 'Investigation of Polarization Peculiarities of Jupiter and Saturn.' Works of the Astrophysical Institute of the Academy of Sciences of the Kazakh SSR (in press). 1965, 'About Thermal Radiation of Jupiter'. Astr. Zu., 64. Naumov, A. P., Khijniakov, I. P. 42. 629· 1965, 'About Generation of Radiation of Jupiter'. Astr. Zu., 42, 798. 65. Jelezniakov, V. V. 1964, 'About Configuration of Magnetic Field of Saturn'. Astr. Zu., 66. Jelezniakov, V. V. 41, 995· 67. Zaharov, A. V., Krotikov, V. D., Troitskij, V. S., Tsejtlin, N. M. 1964, 'Results of Measurements of Radio-emission Intensity of a Number of Discrete Sources of the Moon and Jupiter on wave 70, 16 em'. Izv. Vyssih Uceb. Zaved. Radiofiz., 8, 553· 1964, 'Temperature of Radio68. Krotikov, V. D., Troitskij, V. S., Tsejtlin, N. M. Emission of the Moon and Jupiter on wave 70, x6 em'. Astr. Zu., 41, 951. 1964, 'Radiolocation of the Planet of Jupiter'. Dokl. Akad. Nauk 69. Kotelnikov,V. A., et al. SSSR, 155, 1937. 'Modern State of Problem on Structure and Order of Thickness of 70. Bobrov, M. S. Saturn's Rings'. Works of the Astrophysical Institute of the Academy of Sciences of the Kazakh SSR (in press). 'About Observations of Saturn's Rings in the Period of Passing the 71. Bobrov, M. S. Earth and Sun through their Plane and in the Period of Visibility of Non-Illuminated Part of Rings'. Cirk. V AGO (in press). 72. Gretchushnikov, B. N., Moroz, V. 1., Shniriov, G. D. 1964, 'Investigation of Infra-Red Spectrum of Saturn by Fourier Transformation Method'. Astr. Cirk., Moscow, no. 302. 1965, 'Radio-Emission of Saturn 73· Kutuza, V. G., Losovskij, B. L., Salomonovitch, A. E. on 8-mm Wave', Dokl. Akad. Nauk SSSR, x6x, 1031.

Laboratory and Theoretical Research, Cosmogonical Problems 74· Mitrofanova, L.A., Jukova, A. N., Derviz, T. E. 1964, 'Installation and Testing of Optic Pipe with Considerable Way of Absorption for Investigation of Molecular Spectra'. Izv. glav. astr. Obs. Pulkove, 23, no. 175, 8o. 75· Alexandrov, U. V., Garaja, V.I. 1965, 'Polydispersive Indicatrices of Light Dispersion'. Vestnik Karkovsk. gos. Univ., No.4, Ser. Astr., no. I, 91. 1964, 'Approximate Solution of Problem on Diffuse Reflection and 76. Janovitskij, E. G. Light Transmission through Planets' Atmospheres when Dispersion lndicatrix is Arbitrary'. Vestnik Karkovsk. gos. Univ. Collection 'Physics of the Moon and Planets', Publishing House 'Naukova Dumka', Kiev, p. 92. 77· Sobolev, V. V. 1964, 'Investigation of Atmosphere of Venus'. Astr. Zu., 41, 97· 1963, 'To the Theory of Light Dispersion in Planets' 78. Minin, I. N., Sobolev, V. V. Atmospheres'. Astr. Zu., 40, 496. 79· Sobolev, V. V., Minin, I. N. 1962, 'Dispersion of Light in Spherical Atmosphere', Collection 'Satellites of the Earth', issue 14. So. Minin, I. N., Sobolev, V. V. 1963, 'Dispersion of Light in Spherical Atmosphere, II', Kosmichiskie Issledovaniya, x, no. 2, 227. 1964, 'Dispersion of Light in Spherical Atmosphere, III'. 8x. Minin, I. N., Sobolev, V. V. Kosmichiskie Issledovaniya, 2, no. 4, 6xo. 1965, 'About Dispersion of Light in Planets' Atmospheres'. Trudy astr. 82. Minin, I. N. Obs. Leningrad. Univ., 22, 39· 83. Levin, B. Ju. 1966, 'Accumulation of the Solar Nebula'. International Geophysical Dictionary. Pergamon Press. 1964, 'The Problem of Densities and Composition of Terrestrial Planets 84. Levin, B. Ju. in the Light of Modern Ideas on the Origin of Meteorites'. Icarus, 3, 198. 85. Safronov, V. S. 1966, 'The Protoplanetary Cloud and its Evolution'. Astr. Zu., 43, no. 4· 86. Safronov, V. S. 1966, 'Dispersion of Speeds of Asteroids and the Problem of their Origin'. Collection 'Problems of Motion of Small Bodies of Solar System'. Publishing House of the Academy of Sciences of the Azerbaijan SSR, Baku.

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87. Safronov, V. S. 1964, 'Primary Inhomogeneities of the Earth's Mantle'. Tectonophysics, 1(3), 217. 88. Safronov, V. S. 1965, 'Sizes of the Largest Bodies Dropped on Planets in the Process of their Formation', Astr. Zu., 42, 1270. 1965, 'About Nature of Thermal Inhomogeneities in the Entrails of the 89. Ruskol, E. L. Earth'. Information of the Academy of Sciences of the U.S.S.R., Ser. 'Physics of the Earth', No. 4, pp. 1-8. 90. Kozlovskaja, S. V. 1963, 'Masses and Radii of Planets and Satellites'. Bjull. Inst. teor. Astr., 9, 330. 91. Kozlovskaja, S. V. 1966, 'Models of Inner Formation of the Earth, Venus and Mars'. Astr. Zu., 43, no. 4· 92. Majeva, S. V. 1963, 'About Possibilities of Heating-up Bodies of Asteroid Sizes with the Help of Long-Lived Radioactive Elements'. Information of the Committee on Physics of Planets, no. 4, p. 40. 93· Majeva, S. V. 'Some Calculations of Thermal History of Mars and the Moon'. Dokl. Akad. Nauk SSSR, 159, 294, 1964; The detailed description may be found in the Information of the Committee on Physics of Planets of the Astronomical Board, issue 5, 1966.

17. COMMISSION DE LA LUNE PRESIDENT: Dr D. H. Menzel, Harvard College Observatory and Smithsonian Astrophysical Observatory, Cambridge, Mass. 02138, U.S.A. VICE-PRESIDENTS: Dr A. Dollfus, Dr K. Koziel. SECRETAIRE: Dr B. Bell. CoMITE n'ORGANISATION: D. Martynov, M. G. J. Minnaert. MEMBRES: Arthur, Ashbrook, Barabashov, Boneff, Botelheiro, Drofa, Dzapiashvili, Eckert, Ezersky, Fielder, Focas, Gold, Gunther, Guth, Habibulin, Hall (R. G.), Heyden, Hirose, Hopmann, Ingrao, Jeffreys, Kopal, Kuiper, Levin, Liddel, Link, Markowitz, Murray, Nefediev, Nicholson, O'Keefe, Pettengill, Potter, Rosch, Sadler (F. M. McBain), Sagan, Sato, Schrutka-Rechtenstamm, Sharonovt, Shoemaker, Sinton, Sytinskaya, Troitsky, Ueta, Urey, Watts, Weimer, Whipple, Whitaker, Yakovkin (A. A.). Stimulated by the successful missions of several lunar probes, the field of lunar research has developed tremendously since the formation of Commission 17 at the Hamburg Meeting of the IAU. So many papers have appeared that it becomes difficult to organize and impossible in any reasonable time to digest the literature, particularly with the variety of new techniques coming into use. By way of partial compensation we have added to the references identifying numbers (when available) by which an abstract may be found in Physics Abstracts (P) and/or one of the NASA Abstract publications (A, N). We also call attention to the NASA continuing bibliography (S). Abstracts for many earlier publications can be found in (U). We are indebted to Dr E. L. Ruskol for a report on the study of the Moon in the U.S.S.R. from which we insert paragraphs in the appropriate sections below. A. BOOKS, CONFERENCE PROCEEDINGS In April 1965, Commission 17 of the IAU joined with NASA to sponsor a symposium on the nature of the lunar surface (8). In May 1966, COSPAR sponsored a symposium in Vienna on the Moon and planets (14). A number of other books have appeared that deal in whole (x, 3, 4, 5, 7, xo) or in part (z, 9, n) with a variety of problems of lunar research. Many of the articles appearing in the proceedings of the conferences (3, 8, 9) are referenced individually in the appropriate section below. Kopal (6) has published an atlas of lunar photographs from plates taken at the Pic du Midi Observatory. Scientists of the Central Astronomical Observatory of the Academy of Science of the Ukrainian SSR compiled two books (12, 13) on the shape and motion of the Moon, following an all-Union conference on this topic in Kiev in May 1964. B. LUNAR PROBES a. Hard Landings The greatest achievement in lunar research has unquestionably been the successful missions of several Moon probes launched by the United States of America and by the Soviet Union. A preliminary report on the first successful hard-landing probe, Ranger VII on 31 July 1964, was presented at the Hamburg meetings. The data secured by Ranger VII have been published in a series of three photographic atlases (x) and a volume of interpretive analysis (z). The area selected for impact was a relatively smooth mare, known to have several ray systems and ridges and a relatively high crater density, a region since named Mare Cognitum. 'Craters are the dominant topographic features of the mare surface at all scales down to the smallest 341

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features observed in the last photographs (less than I m across) . . . Craters are more abundant in the rays than in the areas between the rays. The number of craters increases . . . rapidly with decreasing crater size . . . Most of the craters smaller than 250 or 300m in diameter . . . have smoothly rounded rims . . . and a large variation in depth-to-diameter ratio . . . Some of these craters are surrounded by bright halos . . . ' (2). The lunar maria can be characterized (Ha 17) as 'red' or 'blue' on the basis of a slight shift to the red or blue in their reflected solar spectra. Ranger VII impacted a red mare. Fo Ranger VIII the target of the blue Mate Tranquillitatis was selected, and for Ranger IX the Crater Alphonsus (5). The Ranger VIII and IX missions impacted their selected target areas on 20 February I965 and 24 March I966, and returned to earth 7I37 and 58I4 photographs, respectively. These are published in two atlases (3, 4), with a separate volume of interpretive analysis (5). Most of the chapters of (5) as well as other analyses of the Ranger photographs are referenced separately below; see especially refs. (D 32; Ha 6, 10, 12, 15, 16; Hb 3, 5, 8, 16, 17, 22, 23, 31, 32, 37, 46, 47; He 2, 3, 6, II, 13; I 15, 34, 39, 49, 52, 53). Other general discussions of the Ranger missions are presented in (6, 10, II, 13), while (7, 8, 9o 12, 14, 15) emphasize the general interpretation of the new high-resolution photographs.

b. Soft Landings The successful soft landing on the Moon by the Soviet Union's Luna 9 spacecraft on 3 February 1966, enabled earthmen for the first time to see millimeter-sized details of the lunar surface. Luna 9 landed in the western part of Oceanus Procellarum, a region in the immediate neighborhood of the broken ridge that ends southeast of the crater Cavalerius F, so that the photographs cannot with certainty be referred to either a pure mare or a pure mountain surface (7). Preliminary results from Luna 9 have been published in a book (1) that contains a description of the apparatus, of the photogrammetric methods used for the construction of topographic charts on the landing place, and an illustrated description of its morphological features. The photographs have a resolution of I -2 mm for the nearest details. On this scale the surface is very rough indeed, but becomes smoother for the larger scale. This conclusion confirms those reached from earth-based observations. No dust was detected. The bearing strength of the surface is sufficient for the soft landing. However the station later slightly shifted its orientation, probably because of some deformation of the lunar soil. Gold and Hapke (5) interpret the shift of the instrument as evidence that the lunar subsurface may contain many cavities which are in a precarious state of equilibrium. Lipsky infers (7) a bearing strength of the surface of several kgfcm 2 from the fact that most of the small rocks have not noticeably depressed the surface under them. He finds 'no fairy castles, no heaps of angular fragments, sand or loose dust or like forms . . . The photographs show that the surface is not the result of fusion of deposited fine dust, for almost all the objects have regular forms, not branched or random ones. Many depressions of various sizes are clearly visible . . . with many rocklike objects' (7). Davies et al. (z) discuss the signals received from Luna 9 at Jodrell Bank. Fielder et al. (3) comment on the similarity of the terrain revealed by Luna 9 to the scoriaceous surface of an aa (Hawaii) type lava flow. The resemblance to a lava flow is also noted by Kuiper et al. (6) who conclude that the surface shown by Luna 9 is a highly vesicular igneous rock, and clean of dust. Gault et al. (4) infer that the lunar surface consists of non-cohesive to weakly cohesive, poorly sorted fragmental material of unknown source and a depth of at least 20 em, with most of the fragments having sizes less than 1 em. Shoemaker et al. (8) note that the individual fragments could be light and frothy or dense and solid. See also (I 32, 52).

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On 2 June I966, the U.S. Surveyor I landed softly inside the Flamsteed ghost ring, about 500 miles from the site of Luna 9· By 5 June Surveyor I had sent back 2500 pictures, while the final picture count surpassed IO ooo. 'Beautifully clear and sharp, the pictures revealed an eerie, rubble-strewn wasteland stretching level in all directions' (Io). Analysis and evaluation of the data returned during Surveyor's first five days on the Moon (9) indicate that the terrain within I-2 km of the landing site is 'a gently rolling surface studded with craters, with diameters from a few centimeters to several hundred meters, and littered with fragmental debris ranging in size from less than I mm to more than I m. The larger craters resemble those seen in the Ranger photographs in shape and distribution . . . The surface is composed of granular material of a very wide size range; coarse blocks of rock and smaller fragments are set in a matrix of fine particles too small to be resolved. This material was disturbed and penetrated by the footpads of the spacecraft to a depth of a few em .. .' The static bearing capacity of the soil is estimated at about 5 lbfin 2 (I/3 atm). Counts have been made of rocks as a function of size. The exterior of Surveyor I has remained clean and essentially dust free. A tiny nitrogen jet that was fired at the surface near one foot of the spacecraft produced no plume of dust visible to the watching camera (9, IO). Some material disturbed by the footpads was thrown out to form rays . . . darker than the adjacent surface. Photometric and colorimetric observations were obtained. See also (I :u, 52). On 24 December I966, the Soviet Union's Luna I3 made a successful soft landing on the Moon, and is sending back pictures of good quality. A probe rod, to test the firmness of the lunar ground, was reported unable to penetrate far into the rocky ground. Luna I 3 is reported to carry also a special apparatus for measuring the density of lunar rocks. c. Far Side of the Moon

In July I965 the Soviet space probe Zond-3 photographed most of the area of the far side of the Moon not previously recorded by Lunik 3· The new pictures, with a resolution of about 3 km, fully confirm the earlier conclusion that the far side of the Moon has far fewer maria than the near side, and is in general lighter, more mountainous and more densely cratered. Two features not seen on the earthward side are of particular interest: chains of large (10-30 km) craters extending up to I500 km in length; and numerous large("'"' soo km) depressions, named thalassoids, in size and shape similar to maria, but different in having crater-scattered floors and lacking the dark color of maria (I, 4, 5). Measurements of the UV spectrum by a spectrophotometer {I900 to 275oA) and by a spectrograph (2700-3550A) gave a decrease in albedo from s% at 355oA to 3"5% at 3400-3IooA and to I% at 285oA. The albedo increases to 2% at 24ooA and decreases again to I% at 2oooA (2). Infrared spectra at 3-4fL were also obtained by Zond-3. Hartmann (3) discusses the origin of lunar basins and thalassoids, the history of huge concentric structures, and the origin of radial and grid systems of lineaments on the lunar surface, with reference to the structures of the far side. d. Orbiters

On 3 April I966 the Soviet probe Luna IO became the first artificial satellite of the Moon, with the orbit inclined 7I 0 54' to the lunar equator, with a periselenium distance of 350 km and aposelenium of IOI7 km from the surface, and a period of 2h ssm ISS (I). After 460 revolutions, on 30 May 1966, the orbital elements were 72° 2', 378·7 km, 985·3 km, and 2h sSm 36 • A preliminary analysis of the orbital evolution indicated that gravitational anomalies of the Moon are small (3). Preliminary results of measurements by Luna IO gave the following magnetic field intensities (in 10-5 gauss) FF

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5 April 24

9 April 17

The increase in intensity in the period 5-6 April was possibly caused by the passage of the Moon through the magnetic tail of the Earth. Perhaps also as a result of that passage, the registered densities of electrons with energies of the order of 104 eV exceeded the interplanetary background by a factor of 70-100. The density of micrometeoroids measured by acoustic counters was nearly 100 times higher than that in the interplanetary space (z). The total y-radiation intensity of the lunar surface measured by a y-spectrometer is I·5-2·o times that measured over granite rocks. But only 10% of it can originate from the decay of radioactive elements U, Th, K 40 , and 90% must be attributed to the radioactivity induced by cosmic rays. The abundance of radioactive elements in rocks on maria is similar to that in basalts. On the continents this abundance is lower and corresponds to that in ultra-basic rocks. Local variations in the total intensity of the lunar y-radiation (induced + natural) do not exceed 40% (4, 5, 6). On I4 August I966 the United States' Orbiter I became an artificial satellite of the Moon in an orbit inclined IZ·I6° to the equator, a period of 3h 37m 45 8 , and periselenium and aposelenium distances of I89 and 1865 km; these figures were changed to 3h zorn, 58 km and I848 km on 2I August. Orbiter I was equipped to monitor meteoroids and radiation, and to photograph the lunar surface, particularly nine possible landing sites for Program Apollo. Orbiter 1 secured over zoo photographs, many of excellent quality (8, 9), before it was caused to crash on 29 October. Tracking data have been obtained to permit detailed study of the Moon's shape and gravitational field. Preliminary indications, from data of Orbiter's first few days, are that the Moon has a 'relatively large pear-shaped component and that the gravitational properties will be of considerable scientific interest' (xo). See also (M 13). The Moon's third satellite, Luna II, was placed in an orbit inclined 27° to the lunar equator on 28 August 1966, at a height ranging between 159 and IZoo km. We have no information on its mission. Luna 12 was placed in orbit on 25 October I966, and has sent back pictures. On 10 November 1966 Orbiter 2 attained a circumlunar orbit ranging between 1850 and 210 km above the surface, where it served for five days as a passive probe of the lunar gravitational field. On I 5 November the low point of the orbit was reduced to so km for the primary mission of photographing I3 potential landing sites. Orbiter 2 fell silent on 6 December, after transmitting 95% of its scheduled 2I 1 photographs. To date NASA has released a set of spectacular pictures of the region of the crater Copernicus, seen obliquely from a distance of 240 km and a height of 46 km above the Moon with the crater Fauth in the foreground (n). C. CARTOGRAPHY

Arthur and Kuiper report completion of the scheme of lunar nomenclature for the Moon's visible hemisphere, which was proposed and approved by the IAU at its 1964 Hamburg meeting. This nomenclature is embodied in the catalog, The System of Lunar Craters (x), which is in four parts and gives positions and dimensions for 17 ooo craters, and in a two color map in four sheets (z). The compilation of this nomenclature has been a task of some magnitude, and it is hoped that the work will be rewarded by wide acceptance of the new scheme. Other cartographic work by scientists of the Lunar and Planetary Laboratory include selenodetic measures on three Yerkes photographs by Arthur (6, u, 13), drawings of areas of the northwest (19) and southeast (zo) lunar limbs by Herring. Strom (32) has mapped in detail lineaments within 6o 0 of the center of the Moon's face, and delineated four global lineament systems and radial systems associated with four circular maria.

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Since the Hamburg meetings, scientists of the U.S. Geological Survey have accelerated their program of geologically mapping the Moon by telescopic means. Thirty-five maps at a scale of I :I ooo ooo are now published (3) or available in preliminary form (A 7a) out of a planned 44 which will cover most of the earthside hemisphere. Aspects of the geology of selected regions have been discussed (z6, 27, 30, 34, 37, 38, 39). The geological mapping aims to express the structure, history, and formative processes of near-surface materials, and maps class into units those materials believed to have formed simultaneously in about the same way. The units appear in order of relative age. In addition the scientists have employed photographs taken by Ranger VIII for geologic (24, 33, He IJ) and topographic (zs) mapping of a region of Mare Tranquillitatis; and by Ranger IX for the floor of Alphonsus (Hb 8, IJ). See also refs. (Ha n, IZ, IS, I49). The U.S. Air Force, Aeronautical Chart and Information Center has used the Ranger photographs to refine its shaded relief maps of the Moon (4). Their previous maps at a scale of I :I ooo ooo were the largest-scale maps previously available for the impact areas of the Rangers. Their new series (4) possesses scales of I :soo ooo, I :100 ooo, I :10 ooo, and I :1000. These maps 'provide in a condensed, but qualitative, form much of the new topographic data acquired by the Ranger Block III missions' (Bas). References (IS, I7, ZJ) discuss various aspects of the ACIC mapping program. A number of papers discuss various procedures and problems in lunar cartography and selenodesy (S, 7-n, I4, IS, ZI, zz, 3I, 35, 36). Papers (I6, zS, 29) are concerned with the problem of determining elevations on the Moon. See also (Ha s, 8). Lisina and Shevchenko developed van Diggelen's photometric method for the study of relief and applied it to maria regions (40) and the surroundings of the crater Kepler (4I). Markov (42) found the diameter-depth relation: log D = I·o66z log d + o·6zoo, for craters seen on Ranger VII photographs. Mukhamedzhanov and Stanjukovich (43) studied the distribution of primary and secondary ejecta of the crater-forming impact which can explain the double rims of certain craters. Towards an investigation of the geometrical shape of the Moon, Gavrilov (44) developed a method of photography of the Moon and of compiling catalogs of selenocentric positions of details of the lunar surface. After analyzing existing catalogs and adding new measures, he constructed a net of basic points. From measures of I6 photographs of the Moon, with the Schrutka-Rechtenstamm and Baldwin Catalogs as reference, Gavrilov et al. (4S) compiled a catalog of space coordinates of I6o basic points. This was extended to a similar catalog of 500 basic points (46). Gavrilov (47) has compared different systems of position. Lunar Nomenclature

The enormous amount of new data related to the mapping of lunar craters, obtained from the space programs of the U.S.A. and the U.S.S.R. necessitates a complete review of the problem of nomenclature of various lunar features. Recommendations made by special committees of the National Academies of the U.S.A. and U.S.S.R. furnish a starting point for consideration of the problem by the Sub-committee on Lunar Nomenclature of Commission 17 of the IAU under the chairmanship of Z. Kopal. As the result of correspondence undertaken prior to and meetings held during the General Assembly of the IAU in Prague, recommendations will be made to the General Assembly concerning nomenclature for features of the reverse side of the Moon and also of special features on the visible surface. A poll of the membership of Commission 17, undertaken by its president, indicates that the majority favors extension of the present system of nomenclature to the reverse side of the Moon, with craters named for deceased scientists, with special attention to astronomers.

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Barabashov and Ezersky studied the microrelief of different lunar regions (30, 3I) on the basis of V. A. Fedoretz's photometric catalog of 1952. The same authors and Ezerskaya (Fedoretz) (32) studied the reflective properties of 31 areas in Mare Nubium and Mare Cognitum using the Ranger VII photographs, and found that their microrelief does not differ considerably from that of the average lunar surface. Akimov (33) deduced a complicated empiric formula for the brightness distribution at different phase angles, and found it in fairly good agreement with his observations. HameenAnttila et al. (8) studied the shadow effect of surface irregularities, which they found insufficient to explain the observed phase curves, the theoretical curves being more linear and less steep at small phase angles than the observed curves. Hapke (12) modified his earlier (n) theoretical lunar photometric function, by wrinkling the porous, open surface of the previous model into a series of steep-sided depressions. Oetking (I9) found that many terrestrial substances, when observed with an instrument of small aperture, show a prominent rise in reflectivity if the direction of observation is within ± 5° of the direction of the incident light. Hapke (zo) has commented on this conclusion. Wildey (29) made photoelectric measurements in U, B, and V of a number of lunar features extending over a range of morphological types and selenographic coordinates; deviations from the average photometric function have been correlated with stratigraphic class. Ashby (I) determined the average energy reflected by the lunar surface. Rydgren (2I) used the coronagraph at Anacapri to measure the earthshine on the Moon. Opriatova (34) discovered a decrease in albedo towards the ultraviolet in the region 420o-32ooA. Coyne (4) determined differential colors for 36 areas on the Moon, with respect to a standard area in Mare Serenitatis. He found no dependence of the differential colors on phase angle, a result confirmed by Scott (22). Mironova (38) studied the spectral distribution of light reflected from 30 small regions of the lunar surface. Mironova (I7) and Sergeeva (23), from spectrophotometric studies, found signs of luminescence at 425oA and sosoA in the crater Aristarchus. Petrova (35) obtained almost identical spectrophotometric curves for four lunar maria: Tranquillitatis, Crisium, Serenitatis, Sinus Iridum. In the southwest part of Sinus Iridum she found (36) a violet emission band (,\max= 425oA) similar to that in Aristarchus. Near craters Kepler and Le Monnier a green (,\max = 535oA) emission band was observed. She found that some volcanic sublimates containing rock-salt and exposed to ultraviolet illumination showed a luminescence with two maxima, at 426oA and 410oA, resembling that in Aristarchus. See also (I 45). Sharonov and Sytinskaya (37, 24, 25, 27) found that the reflective properties of fresh volcanic crusts studied in field conditions at Kamchatka are similar to those of the Moon, but the roughness of the lunar surface should be much greater. See also (10, 14). Van Diggelen (5) studied the radiance of lunar objects at small phase angles on plates taken during the eclipse of 18 November 1956. The photometric and color properties of several lunar eclipses have been observed (3, 6, I3, 2, I6, IS). Hansen and Matsushima (9) have sought to explain the exceptional darkness and non-reddening of the eclipse of 30 December 1963 by an unusually large extinction in the Earth's upper atmosphere, while Link (IS) invokes lunar luminescence to explain the difference in brightness of various eclipses. Bell and Wolbach (39) call attention to the relation originally found by Danjon between eclipse brightness and color and phase of the sunspot cycle. Matsushima (40, 4I) finds some correlation between the brightness of the eclipsed Moon and the geomagnetic index Kp. See Section I and (J 4, 5) for additional material on the interpretation of photometric observations.

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E. POLARIMETRY

Kokhan (10) published a catalog of the polarization and position angles of the polarization plane of light reflected by 35 areas of the lunar surface at phase angles from -140° to + 140°. Lipsky and Bondarenko (u) found that for many lunar objects at phase angles > 30° the polarization decreases with increasing wavelength; at ± 90° it is 1o-15% higher in the blue than in the red. On the other hand, at angles < 30° the polarization in the red exceeds that in the blue, especially for maria and ray systems. Avramchuk (1) studied the polarization of several lunar areas with color filters and discussed the discrepancies between the data by different authors. Morozhenko (12) measured the polarization of light reflected by different terrestrial rocks. Dzapiashvili and Xanfomaliti (13) used a new electronic polarovisor to obtain lunar images showing the distribution of position angles of the plane of polarization over the disk. Pospergelis (14) designed a new electronic polarimeter for planetary research, which permits the determination of all Stokes' parameters. Clarke (2) has discussed previous data and added new observations on the wavelength dependence of the polarization. Hopfield (7) presented a theoretical interpretation for the negative polarization of moonlight at small phase angles. Marin (8) made polarization measurements of the Moon and planets in the spectral region from o·8 to 11-'· Gehrels, Coffeen and Owings (6) made photoelectric measurements of brightness and polarization on various lunar regions at UBV and 0"941-' wavelengths. Coffeen (3) studied five laboratory samples, three of porous dust layers of ground volcanic cinder particles in 'fairy castle' structures, and two of porous but solid lava fragments. He found the wavelength and phase dependence of the lunar polarization most closely matched by the fairy castle structures; the solid fragment was more highly polarized than the Moon and had essentially no wavelength dependence. Dollfus has presented (5) preliminary results of an extensive study of the polarization of 14 selected regions of the lunar surface at Meudon and Pic du Midi. Complete curves of polarization have been obtained at the wavelengths I"IO, o·g5, o·83, o·6o, and o·551L; measures at o·4o, 0·37, 0·35, and 0"3251-' are in progress. From these data and laboratory study of the polarimetric properties of various substances, Dollfus (4, 5) concludes that the Moon's surface is completely covered in all areas by a layer of small uncompacted, highly absorbing dust particles, whose absorptivity has been increased by the action of the solar wind on the lunar surface. The U.S. Geological Survey has made polarimetric measurements to provide data for the description of lunar geologic units, with emphasis on determination of maximum positive polarization for each unit (9); in general the maximum polarization of a geologic unit is inversely related to its albedo, although occasional exceptions occur. F. THERMAL PROPERTIES AND INFRARED STUDIES

Radiometric and photometric mapping of the Moon at various phases by Shorthill and Saari (22, 18) and by Ingrao et al. (5) has led to the discovery of many thermal anomalies on the surface of the Moon. While detectable at various phases, particularly around the sunset limb, the lunar hot spots are especially striking during total eclipses of the Moon, where they have been extensively studied by Shorthill and Saari (16, 17, 18, 19, 20, 21, 23) at the wavelength region Io-I2f'. They report (18) that more than 400 hot spots have been identified and cataloged. 'Most of them are craters that appear visually bright at full Moon; some have ray systems, some bright interiors, and some bright rims' (18). A substantial percentage were not associated with major ray craters (16), with a marked concentration in Mare Tranquillitatis (21). Some substantial anomalies are identified with quite small craters (18). It is suggested that the thermal anomalies have the properties of bare rock, without an insulating layer of

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dust. Other scientists {I, 26, 29) suggest that the thermal anomalies may arise from lunar roughness on a centimeter scale rather than from special thermal composition or the presence of local thermal sources. Markov and Khokhlova (8) measured the emission near 3·6p. and 8-13p. during the eclipse of 7 July 1963, and obtained a relatively high albedo at 3·6p. of o·3. They found the maria remained warmer by several degrees than the highlands during the eclipse. They detected (9) also a difference in the heating rate of the east and west limbs of the Moon during this eclipse, an anomaly they attribute to differences in the physical parameters. Several scientists studied the lunar surface in the near infrared. Moroz ( IO) measured spectra of selected regions at full Moon and found an increase in albedo with wavelength out to 2·2p., which was very similar for a variety of lunar structures-maria, highlands, and bright craters-that differ considerably in absolute albedo. Binder et al. (2) found the color of the Moon to be very uniform in the region x·o-2·2p., with a few exceptions. From observations made on the second flight of Stratoscope II, Wattson and Danielson (28) also find that the lunar albedo is substantially higher in the infrared out to about 2"5JL than in the visual. Moroz (Io) found that volcanic ash and slag display a variation in albedo with wavelength similar to that of the lunar surface. Wattson and Hapke (27) and Binder et al. (2) investigated the infrared characteristics of terrestrial rocks and simulated lunar surface materials. Terrestrial rock samples were generally much less red than the lunar surface in the x·o-2·2p. region. However samples of volcanic rock, irradiated with 2·0 keV H+ ions, corresponding to an equivalent irradiation of the lunar surface for about 2·5 x 105 years, simulated the intensity ratios for the lunar infrared. This experiment supports Hapke's hypothesis that solar irradiation can produce the unusual spectral curve and low albedo of the lunar surface. Burns and Lyon (3) studied the errors introduced into temperature determinations when one assumes that the emissivity of the lunar surface is independent of wavelength. Their calculations for a variety of substances which might reasonably be expected on the surface of the Moon indicates that the emissivity varies significantly. The deviations from blackbody behavior would give calculated lunar temperatures too low by 3"5 to s·S%· Murcray (n) found that the observed radiance of the lunar surface in the 8 to I0"4JL region was not compatible with gray or blackbody radiation at any temperature. He concluded that the emissivity varied from roughly unity at 8·5p. to about o·g at xop.. In a study of the lunar spectrum in the region 8-1 I p., Moroz ( IO) showed that the absorption band of Si0 2 at 9JL is absent, probably because of the pulverized nature of the surface layer. Bolometric measurements by Chistjakov (32) with a resolution of 45 x 15 km 2 did not reveal any thermal anomalies for the crater Alphonsus. Ryadov et al. (14) discuss their measurements in the 8-1 3·5 p. region of the integrated thermal radiation from the Moon over various phase angles, and derive an average disk temperature of the full Moon. Observing the Moon in the 16-24p. window, Hunt and Salisbury (4) found anomalies that suggested differences in chemical composition among several features of the lunar surface. Linsky (6) developed models with temperature-dependent thermal properties to analyze the observations at both the infrared and the radio wavelengths. Troitsky (24) developed a mathematical analysis of the thermal and radio emission data from the surfaces of the Moon and planets. Murray (I3) points out some inconsistencies between the radio-derived temperature of 207 °K used in the foregoing (24) model, and infrared data which give a temperature of about roo °K-as determined independently by Saari (IS) and Troitsky (25)-for the antisolar point of the lunar surface. Measures of the surface temperature during the lunar night were carried out also by Low (7) and by Murray and Wildey (12). The latter used especially sensitive infrared detectors

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to measure the radiance of the shaded lunar surface, and consider the observed pattern of sunset cooling to be inconsistent with the presence of a thick homogeneous layer of dust. They report a number of thermal anomalies, but no systematic nighttime temperature differences between maria and uplands. The presence of thermal anomalies also suggested the existence of regions completely free from strongly insulating dust. G. RADIO STUDIES

This section deals with two major fields of investigation: thermal radiation from the Moon at radio (mm and em) wavelengths, reviewed in (26, 39, 40); and the reflection of man-made radar waves by the Moon, reviewed in ( x8, 30). The distance to the Moon has been measured by radar (n, 24, 42), and by laser (29); reflected light signals were registered by a group of scientists of Lebedev Physical Institute (45). Kokurin et al. (46) discuss methods of determining orbital parameters and the shape of the Moon by optical location. Thermal. A number of papers (x, 20, 22, 27, 31, 41, 48) report observations of thermal radiation at mm wavelengths from the eclipsed Moon. Troitsky (38) elaborated a theory for the radioemission of the eclipsed Moon, which he compares with observations of the 1963 and 1964 eclipses at r·2o mm. He concludes that the average thickness of the porous surface layer is 6 ± 3 meters, and that the density doubles its value at 2-3 em below the surface, with a decrease by a factor 2 in the absorption coefficient for em wavelengths. Observations of thermal radiation from the center of the uneclipsed Moon yielded determinations of the brightness temperature (27, 35, 47). Papers (8, 14, 22, 34) investigate the relative brightness temperatures of selected regions of the Moon. Gary et al. (14) have determined contours of 3 mm brightness over the lunar disk at 14 phases of the Moon, and derived phase curves for a number of latitudes. The average phase lag of 22° indicates that the lunar surface has a very low thermal conductivity (8, q). In addition Drake (8) reports preliminary evidence for a correlation between 3 mm and infrared thermal anomalies, and stresses that the 3 mm observations require for interpretation at least a two-component model and 1-mm structures all over the surface. In a related study, King et al. (22) determined relative brightness temperatures and cooling rates of selected lunar regions during the eclipse of 1963 December 30. Gary et al. (14) found the brightness temperature of the maria to exceed that of the neighbouring highlands by 2·6 ± 0·2° K, at 3 mm. Salomonovich (34, 43) found that at 8 mm the brightness temperature of the maria exceeded that of the continental regions by 1·5 ± 0·5% (averaged over a lunation); for the midnight temperature this excess was 8° K. The corresponding variation in y is no more than 25%· From a study of the polarization of the lunar radioemission at 6·3 em and comparison with previous data at 3·2 em, Gol'nev and Soboleva (44) conclude that the surface is rough on the mm scale. Troitsky and his collaborators at Gorki Radiophysical Institute continued to develop the 'artificial Moon' method for temperature measurements at different radio wavelengths. The temperature gradient with depth was found to be 2-5° /meter, the thermal heat flow from the interior, I x 106 cal cm- 2 s-1 (assuming temperature-independent thermal properties of the porous surface layer). The full list of papers published by this group can be found in reviews (26, 39). Radar. In a study of lunar radar echoes by a delay-frequency analysis, Thompson (37) derived radar scattering maps of the Moon. He finds that mountainous regions reflect r·s to 2 times as much power as maria regions, while certain craters reflect up to ro-20 times the average. From a review of radar observations Hagfors (x8) concludes that the lunar surface is covered by a material having an effective dielectric constant of 2·6 and that the surface undulations

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on the Moon have a mean slope of II-12° on the scale of about 1 meter. He suggests that the enhanced reflectivity found for young rayed craters is caused by both a higher intrinsic reflectivity and a greater roughness in these features. The results of a study of polarization in radar echoes agree with a model consisting of a tenuous top layer at least 10 em thick, supported by a denser underlying layer (I7)· A number of other papers discuss the analysis of radar echoes from the Moon, with emphasis on the laws of geometrical optics in (32, 33) and on a distribution of structure sizes in (2, 3, 23, 4, 5, I9)· Values for the mean slope are derived in (2, 4, IS, 32), while (u, IS, 30, 32) provide values of the dielectric constant. Katz (21) compares the wavelength dependence of the lunar reflectivity with that of various terrestrial surfaces. Taylor (36) investigates anomalies in the Faraday rotation of lunar echoes and the possibility of a relationship to the geomagnetic index Kp. Hagfors (I6) establishes the relationship between the geometric-optic approach and the autocorrelation approach to the analysis of lunar radar echoes for a Gaussian autocorrelation function when the surface has Gaussian height statistics and introduces deep phase modulation on the incident wave. He finds that, if an appreciable amount of small-scale structure is present, the range of scales responsible for the scattering will include an increasing amount of small-scale structure with increasing angle of incidence. A similar conclusion is reached by Fung and Moore (I2), who show that large-scale features determine the return at nearnormal incidence and small-scale features determine that from near grazing incidence. Evans ( u) reports measurements at 1130, 68, 23, 10, 3·6 and o·86 em. At all six wavelengths it appears that part of the echo arises from a highlight located at the center of the Moon's visible disk. A second component comes almost equally from the remaining parts of the surface. The division of power in the two components changes markedly as the wavelength is reduced. At 68 em, So% of the power is returned from the highlight, while at 8·6 mm only 15% can be associated with this component. The angular power spectrum observed for the power from the highlight also changes with wavelength, indicating that the r. m. s. slope of the surface increases as the wavelength is reduced. These observations are interpreted as evidence of a wide range of structure sizes on the Moon. The measurements at decameter wavelengths by Davis et al. (6, 7) provide additional evidence that at radio frequencies the Moon displays a central highlight that contracts and brightens with increasing wavelength. H. SURFACE FORMATIONS

a. General O'Keefe (I3) has reviewed the present understanding of the structure and origin of the Moon. Fielder (4) has reviewed the present state of lunar geology. Kopal (S) reviews the definition of lunar coordinates, methods for determining the exact shape of the Moon, the origin of lunar formations, and other problems of lunar topography. McCauley (n) discusses the nature of the lunar surface as determined by geologic mapping. From a theoretical comparison of lunar and terrestrial surfaces on globes of equal size, Brock (I) concludes that the coarser tectonic patterns of the Earth and Moon are similar. Dietz (2) suggests that there may be structures on Earth that are analogous to both lunar craters and maria. Geyer and Lopik (S) discuss application of methods of geophysical analysis to study of the lunar surface. Khodak (7) discusses the chief structural elements of both sides of the Moon, including walled plains, craters, maria, valleys and fissures. Krejci-Graf (9) discusses primarily rays and crater shapes. Heacock (6) reviews pre-Ranger lunar data and presents a general summary of the Ranger results. Kuiper et al. (Io) discuss particularly the lunar collapse depressions, as well as the structures of maria and craters, and lineaments. Moore (12) compares two lunar crater

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morphologies, based on Ranger IX photographs, and concludes that the lunar surface materials are weakly cohesive to noncohesive. Shoemaker {IS) discusses the pattern of low ridges and troughs observed on the lunar surface in Ranger photographs, and their relation to the larger lineaments. Urey (I6) discusses theories on the evolution and thermal history of the Moon with reference to the Ranger photographs. Whitaker (I7) summarizes conclusions of the Lunar and Planetary Laboratory on the linear grid, rays, craters, and the absence of dust. He presents evidence for a distinction between 'red' and 'blue' maria, and finds evidence that maria are dust-free lava flows from the sharp boundaries between red and blue mare regions. Van Diggelen (3) discusses a statistical method for determining the preferential direction shown by lunar surface formations known as the lunar grid system, and by this method confirms nearly all the systems previously mentioned by Fielder. Rae (14) presents a historical review of work on lunar domes, and a catalog of 113 domes, which he finds normally occur only on maria near the borders or on the floors of lava craters. See also (I 4, 6, 49).

b. Craters The numerous papers on lunar craters fall into three major categories: discussion of individual craters, statistics of crater size and distribution, and hypotheses of the origin of craters. The target of Ranger IX, crater Alphonsus, has been mapped and discussed geologically (3I ). Carr (8) suggests that the alignment of small craters in Alphonsus is strong evidence that many craters were formed by mechanisms originating within the Moon. Ronca (37) concludes that Alphonsus has been deformed by a strike-slip fault of dextral type. The craters Caramuel {I, 33), Dionysius (42), and Aristarchus (D I7, 23) have also received individual attention. The origin of the central peaks of craters has been discussed in terms of faulting and volcanic extrusion (9), and of meteorite impacts (24). Pohn (34) found many crater slopes to have a steepness of at least 37°. Hartmann {I9) finds that the distribution of lunar crater diameters is satisfactorily explained by the impact hypothesis; he attributes a deficiency of small sizes among the oldest craters to a process of erosion. On the other hand, Fielder (I3, I4) finds that craters cluster more than could be expected on the impact hypothesis and he concludes that a substantial proportion of craters must be of internal origin, an interpretation criticized by Byron (7). Ranger photographs have yielded several studies on the distribution (5, 32, 46, 47) and diameter-depth relationship (3, C 42) of craters. Limitations of space prevent us from discussing individually the various papers dealing with aspects of the meteorite hypothesis (2, 10, n, I6, 20, 23, 25, 35, 39, 40), the volcanic hypothesis (4, 6, 12, I7, I8, 30, 43, 44) and other problems (IS, 26-29, 36, 38, 4I, 45) of crater formation, except to note Kopal's suggestion (22) that many smaller craters may be subsidence phenomena, possibly triggered by Moon-quakes following major impacts, rather than due to secondary impacts. See also (I 39-4I) and section J.

c. Maria Shoemaker (n, 12) discusses the fine structure of Mare Cognitum, defining primary and secondary craters on the basis of morphology and distribution, and commenting upon the rarity of small features of positive relief in the Ranger VII photographs. (However a number of small positive-relief features appear on the Orbiter 2 photographs recently released by NASA.) Other discussions of individual maria include Mare Cognitum (2, 3), Mare Tranquillitatis (I3), and Mare Humorum (9, Io); see also (D 32). Several papers (I, 4, 6, 7) discuss possible origins of the maria, while (8) considers the possible origin of rilles, ridges, and domes in relation to maria, and (S) compares maria and continental regions with respect to radio emission.

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d. Ray Systems From a study of the faint ray systems around Mare Imbrium by special photographic techniques, Alter (1) finds sufficient resemblance between these faint patterns and the patterns of craters and bright ray systems to conclude that they are of the same genus; he considers the existence of the faint patterns argues against any hypothesis of a deep dust layer, and also against the hypothesis that the craterlets observed along bright rays are direct results of secondary impacts. Also discussed are the bright rays radiating from certain lunar craters (2), rille complexes (3), ray systems from Ranger VIII photographs (4). In an analysis of radial structures surrounding lunar basins, Hartmann (5) notes that such systems are more developed around presumably younger basins such as Mare Imbrium and Mare Orientale than around older basins, from which he postulates that conditions for producing radial lineaments were optimal during a relatively short period when the basins were flooded. I. PHYSICAL PROPERTIES AND CHEMICAL COMPOSITION OF THE

LUNAR SURFACE

Ruskol (47) reviewed investigations of lunar surface properties carried out in the previous 2-3 years, including results of laboratory simulation of conditions on the lunar surface, and the connection of data on the thermal regime of the Moon's upper layers with the degassing problem of the lunar interior and the history of the lunar atmosphere. On the basis of photopolarimetric observations (E 6), Gehrels (7) postulates a model of the lunar subsurface that is smooth and firm with little or no dust but with an optically thin layer of ionized micron-sized particles electrostatically suspended over the surface, and accreted from interplanetary space. Objections have been raised (28) concerning the electrostatics of lunar particles and the optical properties of this layer. Gehrels (8) replies that most observations can be explained with a tenuous surface texture with interconnected (rather than freely suspended) scattering elements or particles. Sagan (48) suggests that the photometric properties of the Moon may arise from infall of zodiacal dust particles rather than by proton irradiation of existing dust. Glaser (14) analyzes the implications of the absence of atmospheric pressure for structural, physical, and heat-transfer properties of the lunar surface. From a review of optical data on the lunar surface and related laboratory studies, Hapke (27) finds strong evidence that the surface of the Moon is covered with a layer of fine dust. From examination of Ranger VII pictures (15), the distinctive thermal and radar properties of the crater Kepler (16), and a review of various data (17), Gold finds evidence for a substantial layer of dust on the lunar surface. Other discussions of lunar dust and its properties include (29, 30, 31, 32, so, 51, 52): Urey (52) points out that the dust layers postulated by Gold do not necessarily have low physical strength, incapable of supporting a space vehicle. Jaffe (3o--32) discusses aspects of the strength of a lunar dust surface. Smoluchowski (51) suggests that sintering by corpuscular radiation may compact the dust and increase its mechanical strength. O'Keefe (43) attributes the softened appearance of the larger craters to a deposit of ash over the lunar surface, or less probably to erosion. Possible mechanisms of erosion on the Moon are treated in (2, 5, 42). In a study of morphological aspects of the lunar crust, Miyamoto considers such problems as the gas content, viscosity, and differentiation of the original magma (39), the effects on crater formation of decreasing thickness of a silicic crust (41), and suggests that lunar terra is basaltic and maria ultrabasic (40). Paper (46) considers chemical evolution, and (M 28) treats the differentiation of igneous rocks with reference to the Moon. Laboratory studies have been made of the properties-photometric (2o, 23, 26, 44, 45; D 10, 14, 17, 19, 20, 24, 25, 27), polarimetric (E 3, 4, 5), thermal (12, 13, 54; F 27), and

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miscellaneous (1, 3, 18, 29, 33, 42, 47)-of a variety of substances for comparison with the respective properties of the lunar surface. To match the lunar photometric law, Hapke (23) concludes that a surface must consist of extremely small, rough, nearly opaque objects, arranged into a complex surface of low compaction, such as rock dust, and modified in color and albedo by solar proton bombardment (26). On the other hand, Halajian (19) finds radiothermal and photometric data to be compatible with a 'homogeneous underdense-cohesive silicate' model, as of rock froth or sintered slag. From thermal data, Glaser et al. (13) conclude that the surface is not composed solely of unconsolidated particles, but more likely of sintered materials or highly vesiculated rocks. In a study of 23 samples of terrestrial magmatic rocks, Orlova (44) finds that lunar photometric properties most closely resemble those of volcanic slaggy products. Other Soviet workers (D 14, 24, 25, 27) also find the reflective properties of certain volcanic rocks similar to those of the Moon. Reference (54) reviews the literature on the thermal conductivity of various substances, while (12) finds that sintered loose perlite has thermal properties similar to the lunar surface. Paper (38) concerns the interpretation of radio and radar data, and (21) considers various properties of the Surveyor 1 landing site.

J.

LUNAR VOLCANISM

The last few decades have witnessed a spirited and sometimes acrimonious debate between those who maintain that the lunar craters originated in meteoric impact and those who aver that the craters are of volcanic origin. Data from lunar probes seem about to resolve the question. Although it is still too early to make a definite pronouncement, current evidence suggests that both methods of crater production have been active in producing craters and otherwise molding the lunar surface. Scientists of the U.S. Geological Survey report (Han) their mapping to indicate that the lunar surface probably consists of interbedded and interfingering impact and volcanic debris. The observed 'softness' of the high-resolution photographs and the random distribution of crater diameters smaller than 250 meters clearly support the impact theory. On the other hand, the occurrence of large, deep pits with nearly vertical walls, the sharply delineated regions of contrasting color on the surfaces of certain maria, and the scars of field and ghost craters all suggest the action of tectonic forces including extensive lava flows. The observations would appear to rule out the occurrence of extensive transport of dust over the lunar surface. These conclusions are, of course, still tentative. Final decision on the contribution of volcanic processes must await further analysis of existing films and possible exploration of the lunar surface itself by manned or unmanned techniques. In the meanwhile, we should keep an open mind on such questions. Green (9) reviews the current evidence in support of the hypothesis that volcanic processes have played a major role in the modelling of lunar features. Menzel (24) shows that the Moon, if liquid at any time during its history, would probably have cooled from the outside in. The outgassing processes would have formed a light, foamy lava that would have floated on the heavier magma. Subsequent flows of lava, controlled in part by tides, would account for the appearance of maria and the ghost craters. Kuiper (n) points out similarities between Liamana Volcano in Hawaii and various lunar features, and suggests that the secondary craters on the slopes of Liamana are probably caused by impact. From a study of the frequency and distribution of crater diameters, Simpson (21, 22) argues that the majority of craters on the Moon and Mars are of volcanic origin. Vonnegut et al. (23) suggest that gasses escaping from hot lava may condense to form stable aerosols. O'Keefe (16) interprets a dark stripe seen on certain Ranger VII photographs as evidence for recent lunar volcanism, of intermediate or acid type. On the other hand, Dietz

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and Holden (3) express strong doubt that the Moon has either significant internal convection or currently active volcanos. They argue, from the complete or near absence of water, that explosive volcanism is highly unlikely on the Moon. Section H includes additional references on lunar volcanism. Recent laboratory studies suggest that the absence of a lunar atmosphere must be given more consideration in theorizing on the origin of lunar formations. Dobar (4, 5) finds that a simulated basalt and granite magma, allowed to upwell and solidify in a vacuum, has produced a porous material not found in nature on Earth. The photometric curves of this material resemble closely those from the lunar surface. During the vacuum upwelling, Dobar observed color phenomena similar to those reported around Aristarchus (K 8). In a report on further observations of the luminous glow in the crater Aristarchus, Kozyrev (xo) finds both C 2 and H 2 emission and suggests the latter may be emitted from a fumarole within the crater area. See also (K 4). Middlehurst and Burley (13, K 3) made a complete catalog of observed and recorded lunar events-defined as temporary changes in the appearance of a lunar feature-over the past four centuries. Middlehurst (xz) finds no correlation between the occurrence of such events and sunspot numbers, and suggests the events may arise from tidal cracking or crustal deformations, with a release of hot or cold gasses. In a review of evidence for changes on the Moon, Moore (xs) doubts the reality of reported structural changes, such as the vanishing of crater Linne, and long-term changes in the reflectivity. But he considers that the transient outbreaks, like those reported in Alphonsus, are probably real. Deak et al. (2) postulate a volcanic origin for the reddish spots seen (K 8) in the vicinity of Aristarchus, and calculate the energy liberated from the lunar interior in such an event. See section K for additional references on transient phenomena. The origin of tektites found on the surface of the Earth has long been debated. These glassy objects appear to be some form of meteorite. In the absence of any clear-cut alternative theory, several scientists have suggested (x, 6, 7, 14, 17) that tektites originated on the Moon, and further, that their study may contribute to understanding the lunar structure (19, zo). O'Keefe and Adams (x8) suggest that tektites originated in a lunar ash flow. K. LUNAR LUMINESCENCE

The problem of whether the lunar surface produces detectable luminescence has two aspects- the possible existence of transient phenomena induced in some way by flare-associated solar activity; and possible longer period variations related to the sunspot cycle and general level of solar activity. Most of the research deals with the former aspect. A survey of the historical literature turned up 159 dated and seemingly reliable observations of apparent activity on the Moon over the past four centuries (3, J 13). The material was analyzed with respect to solar activity and to tidal action by the Earth (3). The observations of color streaks in the Aristarchus area in late 1963 have been reviewed (8). A search of the literature turned up 16 additional transient events observed between 1783 and 1963 in the vicinity of Aristarchus (6), and negatively correlated with solar activity. A transient increase in brightness around the crater Kepler was observed through a filter centered at 6725A, while control plates at 545oA showed no effect (xo, 9). A subsequent search by similar techniques detected no luminescent phenomena (14). However use of a blink comparator technique has revealed additional color events (zo). By the 'method of line-depths', a variable luminescence reaching as much as 30% of the continuum was observed near 545oA, but no luminescence greater than z% was detected at H01: or the Na D-lines (x6), nor at around 39ooA (18). Other observations interpreted as evidence of luminescence at particular wavelengths have been cited above (D 17, 23, 36); see also (I 45).

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The explanation of these transient phenomena remains controversial (x, 6, 7, 12, 13; L 4). A laboratory study found (5) that some materials luminesce strongly in the red when bombarded by 40 keV protons, but this finding was not substantiated by other investigators (x7). See also (19). A different type of transient phenomenon, the C 2 Swan bands observed by Kozyrev around the crater Alphonsus, has been attributed to explosions of acetylene (4). On the second aspect of the problem, Gehrels et al. (E 6) report that luminescence was detected in the photometry of various lunar regions, and independently confirmed by the polarimetry-under the assumption that the luminescent light is not appreciably polarized. They found the lunar surface to be 1o-2o% brighter (and less polarized) in 1956-59 than in 1963 November-1964 January. The effect was fairly constant from day to day, and thought to vary with the solar cycle. This phenomenon may be related to Danjon's (1922) finding of a relation between phase of the sunspot cycle and brightness and color of the eclipsed Moon (D xs, 39i E 6). Gehrels et al. (E 6) note that the eclipse of 1965 November 18 was reddish and bright, and that of 1963 December 30 unusually dim. (See also D 2, 3, 5, 6, 9, 13, xs, x6, x8.) However opinion differs whether the dark eclipses (D 9) or the bright eclipses (D xs) require more 'explanation.' L. LUNAR ATMOSPHERE AND ENVIRONMENT

Safronov and Ruskol (12) consider the history of the lunar atmosphere formed by gradual degassing of the interior; they conclude that the Moon never had any appreciable atmosphere and that there has been no liquid water on its surface. Gilvarry (I xo) presents evidence in favor of the former presence of water on the Moon. The possibility of detecting a permafrost layer beneath the lunar surface by observations of OH molecules near the Moon has been considered (I 25, 55). Singer (x3) concludes that the only gas in the vicinity of the Moon comes from interplanetary space, and predicts a peculiar type of 'ionosphere' to exist near the Moon, made up of photoelectrons that have insufficient energy to escape and thus are held back by the Moon's electrostatic field. Hinton and Taeusch (8) use a simplified model of the lunar atmosphere to calculate average densities of certain neutral and ionized gases near the Moon's surface as a function of the solar corpuscular flux and taking account of sources of gas in the lunar crust. Michel (9) examines the flow of solar wind plasma about the Moon for two limiting cases. Several authors discuss aspects of interaction between the solar wind and the lunar surface {I4i I 26, so, sx) or lunar field (x, 3· 4· xo, II). See also (J 8). Observations of y-radiation and magnetic field intensity by Luna 10 have been cited above (Bd 2, 4, 5, 6). Luna 9 provides data on the y-radiation from its vicinity (15), much of which is considered a secondary effect of cosmic radiation. Also considered are lunar X-rays (5, 6, 7), radioactivity (I 35), and expected variations in cosmic ray intensity on the Moon (2). M. INTERNAL STRUCTURE

Levin (23, 24) reviews research on such aspects of internal structure and evolution of the Moon as the origin, thermal history, shape, density distribution, and chemical composition of the Moon. Several of these problems are treated also in (x8). From calculations on the thermal history of the Moon, Levin (22) concludes that a period favorable for lava effusions occurred 2·5 to 3·0 x 109 years ago, depending on the content of radioactive elements in the Moon. Papers (x8, 27) also treat the thermal history of the Moon. Fielder (8) considers that Runcom's theory, in which convection cells keep the Moon's surface buoyed up, provides the only satisfactory explanation for the slight bulge of the Moon

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in the direction of the Earth. He further suggests (9) that this convection may also explain the orientation of the two major systems of pan-lunar lineaments. Some theoretical aspects of convection in the Moon's interior are considered in (17, 18). References (4, 15) treat radiative heat transfer within the Moon, while (x6, 27) deal with problems of thermal conduction, (7) is a theoretical investigation of the energy balance in the crust, and (28) considers processes of igneous rock differentiation as applied to the Moon. The shape of the Moon has been reviewed (23, 24), and recently investigated by means of Orbiter I (13, Bd xo), and annular eclipses (3, s). Wildey (29) reviews other methods. From a comparison of observations and new calculations of the motions of the node and perigee, Eckert (6) finds evidence for a large concentration of mass near the surface of the Moon. Koslovskaya (36) considers the density distribution along the radius for some models of the Moon. Shimazu (N 7) analyzes the viscosity distribution within the Moon. Several papers discuss the shape and internal structure (n, 13, 20, 21, 24), the shape and gravity field (2, 12, 26), and the distribution of mass in the Moon (x, 6, xo, 23, 24, 25). Levin postulates that the oblate shape of the Moon is a direct consequence of the decrease of surface temperature from the equator to the poles, with a corresponding absence of spherical symmetry in the distribution of internal temperature (32, 33, A 13). Safronov (34, A 13) considers some isostatically-compensated models of the Moon with a semi-molten core and solid outer parts, the thickness of the latter being greater along the polar axis due to thermal conditions (Levin's suggestion). He showed that such models can account for the observed 'non-equilibrium' oblateness of the Moon. The necessary difference in thickness of the solid layer is in accordance with the calculations on the thermal history of the Moon performed by Levin and Majeva (22, 35). Thus, contrary to a widespread opinion, the Soviet scientists find the semi-molten state of the lunar interior, which follows from thermal calculations for the chondritic model of the Moon, does not contradict its non-equilibrium shape. Zharkov et al. (30) review recent trends in studies of the interior structure of the Moon and planets by geophysical methods. They consider (30, 37) the propagation of seismic waves on the Moon for different temperature conditions of its interior. The existence of a very thick layer of low velocities is suggested. Seismic studies are considered also in (x, 19). Zharkov (3o) considers quantitatively the relationship between the lunar magnetic field and the conditions in the liquid iron core. N. ORIGIN AND EVOLUTION OF THE MOON

Scientists of the 0. J. Schmidt Institute of Physics of the Earth (5, 6, n, 12, 13) made new calculations of the effects of tidal friction in the interior of the Earth and Moon on the evolution of the Moon's orbit. They find that the lunar orbit was formerly smaller, less eccentric, and less inclined to the Earth's equator than now, a result they interpret as favoring the formation of the Moon in the Earth's vicinity, and in contradiction to the Alfven-Gerstenkorn (x) hypothesis on the capture origin of the Moon. The effects of tidal friction are considered also in (4), while (2) presents the hypothesis of origin by capture in a direct orbit at a distance of about 45 Earth radii when the Earth was rotating in about ten hours. Urey (xo) reviews, in the light of recent evidence, his 1957 theory that the Moon was one of the primary objects accumulated in primitive gas spheres and is older than the Earth. In (9) he discusses evidence for the contamination of the Moon by terrestrial water. Shoemaker (8) describes the establishment of a geological time scale for major events on the Moon, by using the technique of stratigraphy. D. H. MENZEL

President of the Commission B. BELL

Secretary of the Commission

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Sources of Abstracts P. Physics Abstracts, publ. monthly by the Institution of Electrical Engineers, London. A. International Aerospace Abstracts, publ. semi-monthly by American Institute of Aeronautics and Astronautics, New York, N.Y. N. Scientific and Technical Aerospace Reports, publ. semi-monthly by NASA, Scientific and Technical Information Division, available from U.S. Government Printing Office, Washington, D.C. S. Lunar Surface Studies: a Continuing Bibliography with indexes. NASA-SP-7003 (oi), March I965; NASA-SP-7oo3 (o2), April Ig66. U. Bibliography of Lunar and Planetary Research, I960-64. Ed. J, W. Salisbury. AFCRL66-52, Special Report No. 40. 524 p. (Moon, p. 257-373), January I966.

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2. Ranger VII. Part II: Experimenters' Analyses and Interpretations. R. L. Heacock, G. P. Kuiper, E. M. Shoemaker, H. C. Urey, E. A. Whitaker. Jet Propulsion Lab. Tech. Rep. No. 32--700. Feb. 1965, 156 p. (N65-22162) 3· Ranger VIII Photographs of the Moon, Cameras A, B, and P. 1966, 478 p., NASA-SP-111. (N66-25366) 4· Ranger IX Photographs of the Moon, Cameras A, B, and P. 1966, 193 p., NASA-SP-x 12. (N66-z6555) 5· Ranger VIII and IX. Part II: Experimenters' Analyses and Interpretations. R. L. Heacock, G. P. Kuiper, E. M. Shoemaker, H. C. Urey, E. A. Whitaker. Jet Propulsion Lab. Tech. Rep. No. 32-8oo, 1 March 1966, 182 p. (N66-25046) The Moon photographed by Ranger VII. L'Astronomie, 79, 41. 1965. 6. Couderc, P. (P65-24334) The surface structure of the Moon. p. 99-105 in ref. AS. (A66-35441) 7· Kuiper, G. P. Lunar results from Rangers VII to IX. Sky and Tel., 29, 293, 1965. S. Kuiper, G. P. (A65-23739) Interpretation of the Ranger records. p. 24-29 in ref. A9. (N66-31448) 9· Kuiper G. P. The Ranger Lunar Missions. COSPAR, 6th Intern. Space Sci. Symposium, IO. Nicks, 0. W. Buenos Aires, May 1965, 54 p. (A65-25918) The Ranger missions to the Moon. 11. Schurmeier, H. M., Heacock, R. L., Wolte, A. E. Sci. Amer., 2I4, 52, 1966. (A66-1836o) The Moon close up. Nat'l. Geographic, I26, No. 5, 690, 1964. I2. Shoemaker, E. M. Eyes on the Moon. Astronautics I3. Smith, G. M., Vrebalovich, T., Willingham, D. E. and Aeronautics, 4, 74, 82, 1966. Observations on the Ranger photographs. p. 3-21 in ref. AS. (A66-35438) I4- Urey, H. C. Observations on the Ranger VIII and IX pictures. p. 1-23 in ref. A9. I5. Urey H. C. (N66-31447)

b. Soft Landings I. The First Panoramic Views of the Lunar Surface (Pervyye Panoramy Lunnoy Poverkhnosti). Moscow, Izd. Nauka, 1966, 132 p. (N66-38486) Observations of the Russian 2. Davies, J. G., Lovell, B., Pritchard, R. S., Smith, F. G. Moon probe Luna 9· Nature, 209, 848, 1966. (A66-23915) The Moon from Luna 9· Nature, 209, 851, 1966. 3· Fielder, G., Wilson, L., Guest, J. E. (A66-23916) Luna 9 photographs4• Gault, D. E., Quaide, W. L., Oberbeck, V. R., Moore, H. J. evidence for a fragmental surface layer. Science, I53, 985, 1966. (A66-40017) Luna 9 pictures -implications. Science, I53, 290, 1966. 5· Gold, T., Hapke, B. W. (A66-40522) Russian Luna 9 pictures 6. Kuiper, G. P., Strom, R. G., LePoole, R. S., Whitaker, E. A. -provisional analysis. Science, I5I, 1561, 1966. (A66-z5137) What Luna 9 told us about the Moon. Sky and Tel., 32, 257, 1966. 7· Lipsky, Y. N. An appreciation of the Luna 9 pictures. S. Shoemaker, E. M., Batson, R. N., Larson, K. B. Astronautics and Aeronautics, 4, 40, May 1966. 9· Surveyor I -preliminary results. Science, I52, 1737, 1966. (A66-z9657) IO. Pictures from the Moon. Sky and Tel., 32, 16, 1966. 11. Some Surveyor findings. Sky and Tel., 32, 63, 1966. c. Far Side Zond-3 photographs of the Moon's far side. Sky and Tel., 30, 338, 1965. I. Lipsky, Y. N. (A66-14023) 2. Acad. Sci. U.S.S.R., Report to COSPAR, Wien, 1966. Lunar basins, lunar lineaments, and the Moon's far side. Sky and 3· Hartmann, W. K. Tel., 32, 128, 1966. (A66-40544) The far side of the Moon seen by Zond-3. L'Astronomie, 79, 421, 1965. 4· Kovalevsky, J. (A66-21755) The far side of the Moon. Flight International, S8, 554, 1965. (A65-34814) 5· Lipsky, Y. N.

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d. Orbiters I. 2.

3· 4· 5· 6. 7• 8. 9· 10. II.

TASS Reports, Pravda, 5 April and 10 April, 1966. Press-conference on Luna-ro, Pravda, 17 April, 1966. Acad. Sci. U.S.S.R. Report, Pravda, 3 June, 1966. Vinogradov, A. P., Surkov, Y. A., Chernov, G. M. Dokl. Akad. Nauk SSSR, 1966, in press. Vinogradov, A. P., Surkov, Y. A., Chernov, G. M., Kirnosov, F. F., Nasarkina, G. B. Geokhimia, No. 8, 1966. Pravda, 14 Sep. 1966. Vinogradov, A. P., Surkov, Y. A. Gors, W., Oberdorfer, H. Luna 10. Sterne und Weltraum, 5, 215, 1966. (A66-40377) Lunar Orbiter surveys the Moon. Sky and Tel., 32, 192, 1966. Lunar Orbiter photographs of the Moon. Sky and Tel., 32, 346, 358, 1966. Michael, W. H., Jr., Tolson, R. H., Gapcynski, J. P. Lunar orbiter -tracking data indicate properties of Moon's gravitational field. Science, 153, II02, 1966. (A66-40302) New York Times, I Dec. 1966; Sky and Tel., 33, 22, Jan. 1967.

C. Cartography 1.

2.

3·

4· 5· 6. 7• 8. 9· 10. II.

GG

The System of Lunar Craters. Quadrant II. Communications of the Lunar and Planetary Laboratory, No. 40, D. W. G. Arthur, A. P. Agnieray, R. A. Horvath, C. A. Wood, C. R. Chapman. March 1964. (N65-18937) Quadrant III. Ibid., No. so. D. W. G. Arthur, A. P. Agnieray, R. H. Pellicori, C. A. Wood, T. Weller. Feb. 1965. (A66-u465) Quadrant IV. Ibid., No. 70. D. W. G. Arthur, R. H. Pellicori, C. A. Wood. May 1966. (N66-38712) Lunar Designations and Positions. Quadrant II. D. W. G. Arthur, A. P. Agnieray, August 1964; Quadrant III. D. W. G. Arthur, A. P. Agnieray, April 1965; Quadrant IV. D. W. G. Arthur, R. H. Pellicori, Sep. 1966. Univ. Arizona Press, Tucson. United States Geological Survey Maps of the Moon: The Riphaeus Mountains region, Map I-458, R. Eggleton, 1965. The Timocharis region, Map I-462, M. H. Carr, 1965. The Montes Apenninus region, Map I-463, R. J. Hackman, 1966. The Aristarchus region, Map I-465, H. J. Moore, 1965. The Pitatus region, Map I-485, N.J. Trask, S. R. Titley, 1966. The Mare Serenitatis region, Map I-489, M. H. Carr, 1966. The Helvelius region, Map I-491, J. F. McCauley, 1967. The Mare Humorum region, Map I-495, S. R. Titley, 1967. The Julius Caesar quadrangle, Map l-510, E. C. Morris, D. E. Wilhelms, 1967. Ranger Lunar Charts. United States Air Force, Aeronautical Chart and Information Center, St. Louis. Ranger VII, RLC 1-5, 1964; Ranger VIII, RLC 6-12, 1966; Ranger IX, RLC 13-17, 1966. Arthur, D. W. G. The reduction of measures for position on a single lunar photograph. Comm. Lunar Planet. Lab., 4, 77, 1965. (A66-29969) Arthur, D. W. G. Selenodetic measures on Yerkes lunar photograph No. II70. Ibid., 4, 81, 1965. (A66-29970) Arthur, D. W. G. The computation of selenodetic coordinates using the librations. Ibid., 4, 89, 1965. (A66-29971) Measures on star-trailed lunar photographs and their initial reductions. Arthur, D. W. G. Ibid., No. 71, Jan. 1966. Arthur, D. W. G. Scale transfer for lunar photographs. Ibid., No. 73, Feb. 1966. Arthur, D. W. G. On the validity of selenodetic positions. Ibid., No. 74, March 1966. Arthur, D. W. G. A method for the determination of the Moon's constants of rotation from measurements on scaled and oriented lunar photographs. Ibid., No. 75, May 1966.

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12. Arthur, D. W. G. Selenodetic measures on Yerkes lunar photograph No. 1269. Ibid., No. 76, July I966. 13. Arthur, D. W. G. Selenodetic measures on Yerkes lunar photograph No. 482. Ibid., No. 77, July I966. Large-scale lunar photogrammetry. Photogrammetric Engineering, 32, 227, 14. Bird, T. H. 1966. (A66-256oi) IS. Bray, T. A., Goudas, C. L. A contour map based on the selenodetic control system of the Aeronautical Chart and Information Center of the U.S. Air Force. Boeing Math. Note No. 457, 20 p., March 1966. (N66-3I4I8) 16. Eckhardt, D. H. On the harmonic analysis of absolute lunar elevations. Icarus, s, 3I3, I966. (P66-28583; A66-330I9) Lunar charting. Air Univ. Rev., 16, 76, I965. (A65-27043) 17. Eriksen, J. G. 18. Goudas, C. L. The selenodetic control system of the U.S. Army Map Service. Icarus, 4, I88, I965. (A65-26047) 19. Herring, A. K. Preliminary drawings of lunar limb areas. IV. Comm. Lunar Planet. Lab., 3, I3, I965. (A66-u496) 20. Herring, A. K. Preliminary drawings of lunar limb areas. V. Comm. Lunar Planet. Lab., 3 , IS, I965. (A66-I I497) Progress in selenodesy. p. 1220-35 in ref. A3. (A65-34276) 21. Hunt, M. S. Photographic resolution on the lunar surface from ground22. Kopal, Z., Rackham, T. W. based facilities. Icarus, 2, 329, 1963. (A64-I4463) Coordinates of lunar features. Icarus, 4, 5I3, 1965. 23. Meyer, D. L., Ruffin, B. W. (A66-I9263; P66-I3I66) 24. Milton, D. J., Wilhelms, D. E. Geology from a relatively distant Ranger VIII photograph. p. 3o2-I3 in ref. Bas. (N66-25055) Experimental topographic map of a small area of the lunar 2S· Moore, H. J., Lugn, R. V. surface from the Ranger VIII photographs. p. 295-302 in ref. Bas. (N66-25054) 26. Morris, E. C., Wilhelms, D. E. Preliminary geologic map of the Julius Caesar quadrangle. ref. A7, map supplement. The Serenitatis Bench and the bond formation. p. 9-12, ref. A7a. 27. Pohn, H. A. 28. Riesen, A. A partial explanation of the divergence between visual and photographic measurements of relative elevations on the Moon. Arch. Sci. Switz., 17, 225, I964. (P6s-1s82s) 29. Rindfleisch, T. Photometric method for lunar topography. Photogrammetric Engineering, 32, 262, 1966. (A66-256o3) Preliminary albedo map of the lunar equatorial belt. p. 101-14 30. Rowan, L. C., West, M. in ref. A7a. 31. Samaha, A. H., Kopal, Z. Lunar photography with the 74-inch reflector of the Helwan Observatory at Kottamia. Icarus, 5, 309, I966. (A66-330I8; P66-28585) 32. Strom, R. G. Analysis of lunar lineaments. !-Tectonic maps of the Moon. Comm. Lunar Planet. Lab., 2, 205, 1964. (A65-23264) 33· Trask, N.J. Preliminary geologic map of a small area in Mare Tranquillitatis. p. 319-26 in ref. Bas. (N66-25057) Preliminary report on the geology of the Byrgius region of the Moon. 34· Trask, N. J. p. 3-8 in ref. A7a. 3S· Triplet, J.-M. Lunar topography and cartography. L'Astronomie, So, 183, I966. (A6632I32). A computer program for the transformation of lunar observations from 36. Wildey, R. L. celestial to selenographic coordinates. Icarus, 3, 136, 1964. (A64-28o18) Fra Mauro and Cayley formations in the Mare Vaporum and Julius 37· Wilhelms, D. E. Caesar regions of the Moon. p. I 3-27 in ref. A7a. Preliminary geologic mapping 38. Wilhelms, D. E., Masursky, H., Bender, A. B., Ryan, J.D. of the easternmost part of the lunar equatorial belt. p. 45-54 in ref. A7a. Compilation of geology in the lunar equatorial belt. 39· Wilhelms, D. E., Trask, N. J. p. 29-34 in ref. A7a. 40. Lisina, L. R., Shevchenko, V. V. p. 8o-9I in ref. Au.

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p. 95-109 in ref. All • Lisina, L. R. Dokl. Akad. Nauk SSSR, 167, No. x, 1966. Markov, A. V. Kosmicheskie Issledovania, 4, 408, 1966. Mukhamedzhanov, A. K., Stanjukovich, K. P. In ref. A1:z. Gavrilov, I. V. In ref. A1:z. Gavrilov, I. V., Duma, D. P., Kislyuk, V. S. 46. Gavrilov, I. V., Duma, D. P., Kislyuk, V. S. In ref. AIJ. In ref. Axa. 47· Gavrilov, I. V.

41. .p. 43· 44· 45·

D. Photometry Energy balance on the lunar surface. Publ. astr. Soc. Pacij., 78, 254, 1966. x. Ashby, N. (A66-38052) Photoelectric observation of the lunar eclipse of 1964 June 24-25. :z. Bouska, J., Mayer, P. Bull. astr. Inst. Csl., 16, 252, 1965. (A65-32576) Intensity and color gradients in the Earth's 3· Cohen, H. L., Dyck, H. M., Young, A. umbra of 1964 December 19. Astr. J., 71, 270, 1966. (P66-28575; A66-32o68) Differential colors on the Moon. Astr. J., 70, us, 1965. (P65-10162) 4· Coyne, G. V. The radiance of lunar objects near opposition. Planet. Space Sci., 5· Diggelen, J. van IJ, 271, 1965. (P65--27804) Photoelectric observations of the Moon during the total lunar eclipse of 6. Feinstein, A. 1964 June 24-25. Bull. astr. Inst. Csl., 17, 163, 1966. (A66-39858) New measurement of the apparent magnitude of the Sun and of the full 7· Gallouet, L. Moon. C. R. Acad. Sci. (France), :zs6, 4593, 1963. (P64-2415) The shadow effect in the phase curves 8. Hiimeen-Anttila, K. A., Laakso, P., Lumme, K. of lunar type surfaces. Ann. Acad. Sci. Fennicae A VI (Finland), No. 172, ISP· 1965. (P65-27812) Light illuminance and color in the Earth's shadow. J. 9· Hansen, J. E., Matsushima S. geophys. Res., 71, 1073, 1966. (A66--22570) Photometric studies of complex surfaces, with applications xo. Hapke, B. W., Van Horn, H. to the Moon. J. geophys. Res., 68, 4545, 1963. (P64--2394) A theoretical photometric function for the lunar surface. J. geophys. Res., 11. Hapke, B. W. 68, 4571, 1963. (P64-2395) An improved theoretical lunar photometric function. Astr. J., 71, 333, x:z. Hapke, B. W. 1966. (P66-32296) Three-color photometry of the 1960 March lunar eclipse. Publ. astr. IJ. Hardie, R. H. Soc. Pacif. 76, 257, 1964. (P65-10164) Spectrophotometric comparison of the lunar surface with certain volcanic 14. Lebedeva, I. I. flows. Trudy astr. Obs. Leningrad. gos. Univ., 2:1, 99, 1964. (A65-25695) Two remarks concerning the terrestrial shadow on the Moon. Bull. astr. Inst. xs. Link, F. Csl., :17, 161, 1966. (A66-39857) The eclipse of the Moon, 1964 June 24-25. L'Astronomie, 79, x6. Marin, N., Zahn, J. P. 14, 1965. (P65-15826) Spectrophotometry of details on the lunar surface. p. 16--29, in ref. :17. Mironova, M. N. Az. (A6s-18969) The partial lunar eclipse of 1965 June 13-14. J. Brit. astr. Assoc., 75, 339, x8. Moore, P. 1965. (P66-6o6o) Photometric studies of diffusely reflecting surfaces with applications to the xg. Oetking, P. brightness of the Moon. J. geophys. Res., 7:1, 2505, 1966. (P66-25153) Comments on paper by Philip Oetking, 'Photometric studies of diffusely :zo. Hapke, B. W. reflecting surfaces with applications to the brightness of the Moon'. J. geophys. Res., 7:1, 2515, 1966. Photometric measurements of earthshine on the Moon. Stockholms Obs. :zx, Rydgren, B. Medd., No. 154. Colour on the Moon. Nature, :204, 1075, 1964. (P65-10161) :z:z. Scott, N. W. Spectral investigations of the lunar surface. p. 3o-45 in ref. A:z. :ZJ. Sergeeva, A. N. (A6s-1897o)

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Some results of photometric and colorimetric comparison of terrestrial 24. Sharonov, V. V. volcanic crusts with the lunar surface. p. 74o-5o in ref. A3. (A65-34248) A photometric investigation of the presence of outer layers of volcanic 25. Sharonov, V. V. origin on the Moon. Astr. Zu., 42, I36, I965. (P6S-I374I; A6s-zo6s6) Albedo values for separate features of the lunar surface. Astr. Zu., :z6. Sytinskaya, N. N. 40, Io83, I963. (P6s-4626) Photometric data for and against the presence of widely distributed 27. Sytinskaya, N. N. volcanic activity on the Moon. p. 756-767, in ref. A3. (A65-34250) The Moon's photometric function. Nature, :zoo, I056, I963. (P64-23890) :zS. Wildey, R. L. Detailed photoelectric photometry of the Moon. Astr. J., 29. Wildey, R. L., Pohn, H. A. 69, 619, I964. (A65-26789) Zirk. Kharkov Obs., No. 25, I962. 30. Barabashov, N. P., Ezersky, V. 1., Prishljak, N. P. Vestnik Kharkov Gos. Univ., No. 4, issue I, ser. 31. Barabashov, N. P., Ezersky, V. I. astr., 22-42, I965. a:z. Barabashov, N. P., Ezersky, V. 1., Ezerskaya, V. A. Ibid., issue 2, 12-25, I965. Ibid., issue I, 43-6I, I965. 33· Akimov, A. A. Ibid., 62-64. 34- Opriatova, V. S. Izv. glav. astr. Obs. Pulkove, 24. I68, I965. 35· Petrova, N. N. Ibid., No. I82. 36. Petrova, N. N. Izv. Komissii po Fisike Planet, issue 4, 24, I963. 37• Sharonov, V. V. Spectral reflective characteristics of the lunar surface. p. 5-u in ref. aS. Mironova, M. N. An. Lunar eclipses and the forecasting of solar minima. Icarus, 39· Bell, B., Wolbach, J. G. 4, 409, I965. (P66-6I2I) Apparent correlation between the lunar eclipse brightness and the 40· Matsushima, S. solar wind. Nature, :zn, I027, I966. Variation of lunar eclipse brightness and its association with the 41. Matsushima, S. geomagnetic planetary index Kp. Astr. J., 71, 699, I966.

E. Polarimetry I.

:z. 3· 4· 5· 6. 7· S. 9· IO.

n. I:Z. IJ.

:1:4.

Polychromatic polarimetry of some lunar areas. p. 3-I5 in ref. A:z. Avramchuk, V. V. (A65-I8968) Studies in astronomical polarimetry, III. The wavelength dependence of Clarke, D. the polarization of light reflected by the Moon and Mars. Mon. Not. R. astr. Soc., IJO, 83, I965, (P65-33883) Wavelength dependence of polarization, IV. Volcanic cinders and Coffeen, D. L. particles. Astr. J., 70, 403, I965. (P65-27794; A65-324n) The alteration of the polarimetric properties of the lunar Dollfus, A., Geake, J. E. surface under the action of solar protons. C. R. Acad. Sci., :z6o, 492I, I965. (A65-25246) The application of polarized light for the study of the surface of the Moon. Dollfus, A. . p. I9-30 in ref. AS. (A66--35445) Wavelength dependence of polarization. III. Gehrels, T., Coffeen, T., Owings, D. The lunar surface. Astr. J., 69, 826, I964. (P65-Ioi63; A65-30647) Mechanism of lunar polarization. Science, 151, I38o, I966. (P66-2207I) Hopfield, ]. ]. Photoelectric measurements of polarization with a coude telescope of I m. Marin, M. Rev. Opt., 44· II5, I965. (P65-31234) Polarization properties of some lunar geologic units. Wilhelms, D. E., Trask, N. J. p. 63-80 in ref. A7a. Izv. glav. astr. Obs. Pulkove, 24, issue 2, No. I78, I82, I965. Kokhan, E. K. Sooblc. gos. astr. Inst. P. K. Sternberga, I966 (in Lipsky, Y. N., Bondarenko, L. N. press). Investigation of polarizable properties of light reflected by various Morozhenko, A. V. specimens of terrestrial rock. p. 70-82 in ref. An. p. 275 in ref. AS. Dzhapiashvili, V. P., Xanfomaliti, L. V. Astr. Zu., 42, 398, I965. Pospergelis, M. M.

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:n. King, H. E., Jacobs, E., Stacey, J, M. 23. 24· 25. 26. 27.

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370

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Morphological aspects of the lunar crust. Icarus, 3, 486, 1964. (A65-17769) 39· Miyamoto, S. Morphological aspects of the lunar crust. II. Icarus, 4, 421, 1965. 40. Miyamoto, S. (A65-35368) 41. Miyamoto, S. Morphological features of the libratory region of the Moon. p. 776-96 in ref. A3. (A65-34252) 42· Naughton, J. J., Barnes, I. L., Hammond, D. A. Rock degradation by alkali metals -a possible lunar erosion mechanism. Science, 149, 630, 1965. (A65-33343) Lunar ash flows. p. 264-6 in ref. AS. (A66-35451) 43· O'Keefe, J. A. 44• Orlova, N. S. Characteristic light-scattering curves for certain magmatic rocks. Trudy astr. Obs. Leningrad. gos. Univ., ::u, 74, 1964. (A65-25693) 45· Petrova, N. N. Spectral investigations of the lunar surface. Astr. Zu., 43, 162, 1966. (A66-235o6; P66-19065) 46. Ringwood, A. E. Chemical evolution of the terrestrial planets. Geochim. Cosmochim. Acta, 30, 41, 1966. (A66-19075) 47· Ruskol, E. L. Physical properties of the lunar surface. Kosmicheskie Issledovaniya, 3, 395, 1965. (P65-22o68; A65-358o9) 48. Sagan, C. Photometric properties of Mercury. Astrophys. J., 144, 1218, 1966. Progress in the analysis of the fine structure and geology of the lunar 49· Shoemaker, E. M. surface from the Ranger VIII and IX photographs. p. 3o-1 in ref. A9. (N66-3 1449) so. Smoluchowski, R. Radiation sintering of lunar dust. Science, 150, 1025, 1965. (P66-13167; A66-I3338) 51. Smoluchowski, R. Structure and coherency of the lunar dust layer. J. geophys. Res. 71, 1569, 1966. (A66-24892; P66-22069) 52. Urey, H. C. 'Dust' on the Moon. Science, 153, 1419, 1966. (A66-41309) 53· Walker, E. H. Comments on the photographs obtained by Ranger VII. Astronautyka, 8, 3, 1965. (A65-24419) 54· Wechsler, A. E., Glaser, P. E. Pressure effects on postulated lunar materials. Icarus, 4, 335, 1965. (A65-35359; P66-6o63) On the detection of water on the Moon. Cornell55· Werner, M., Gold, T., Harwit, M. Sydney University Astronomy Center Report No. 44, 16 p., July 1966.

J.

Lunar Volcanism

x. Adams, E. Origin of lunar tektites. Raumfahrtforschung, xo, 105, 1966. (A66-38059) 2. Deak, G., Erdosi, K., Fiiredi, M., Hedervari, P., Sugar, I. Some energetical calculations regarding the recent volcanic phenomena of the Moon. Gerlands Beitriige zur Geophysik, 75, 122, 1966. (A66-34099) 3· Dietz, R. S., Holden, J. C. Earth and Moon -tectonically contrasting realms. p. 631-40 in ref. A3. (A65-34242) 4· Dobar, W. I. Behavior of lava on the lunar surface. p. 495-515 in ref. A3. (A65-34233) 5· Dobar, W. I. Simulated basalt and granite magma upwelled in vacuum. Icarus, 5, 399, 1966. (A66-38025) The lunar origin of tektites. Icarus, 4, 317, 1965. (A65-29u2) 6. Gilvarry, J. J. 7· Gilvarry, J. J. The lunar origin of tektites. p. 1061-81 in ref. AJ. (A65-34267) 8. Gold, T. Outgassing processes on the Moon and Venus. p. 249-55 in The Origin and Evolution of Atmospheres and Oceans. Eds. Brancazio, P. ]., Cameron, A. G. W. New York, John Wiley and Sons, 1964. (A65-33298) 9· Green, J. Tidal and gravity effects intensifying lunar defiuidization and volcanism. p. 403-69 in ref. A3. (A65-34230) IO, Kozyrev, N. Volcanic phenomena on the Moon. Nature, 198, 979, 1963. (P64-4883) II. Kuiper, G. P. Volcanic sublimates on Earth and Moon. Comm. Lunar Planet. Lab., 3, 33, 1965. (A66-usoo) x2. Middlehurst, B. M. Transient lunar events: possible causes. Nature, 209, 602, 1966. (P66-25155) IJ. Middlehurst, B. M., Burley, J. M. Chronological listing of lunar events. NASA-TMX-55470. Apr. 1966, 46 p. (N66-24927)

LA LUNE

371

Tektites -their nature and possible origin. J. Brit. astr. Assoc., 76, 73, :r4- Mills, A. A. 1966. (A66-278:~3) An evaluation of the reported lunar changes. p. 797-810 in ref. A3. :rs. Moore, P. (A6s-342s3) Interpretation of Ranger photographs. Science, :r46, SI4, 1964. (P6s-4622) :r6. O'Keefe, J. A. Tektites and impact fragments from the Moon. Sci. American, :uo, :r7. O'Keefe, J. A. so, 1964. (P6s-464s) Tektite structure and lunar ash flows. J. geophys. Res., :r8. O'Keefe, J. A., Adams, E. W. 70, 3819, 196s. (A6s-32671) Tektites as a guide to the structure of the Moon. :r9. O'Keefe, J. A., Lowman, P. D., Jr. Tectonophysics, 2, 319, 196s. Lunar structure as deduced from Muong Nong Tektites. p. 20. O'Keefe, J, A., Adler, I. 92-101 in ref. A9. (N66-314s6) Evidence for the volcanic origin of lunar and Martian craters. Earth :z:r. Simpson, J. F. Planet. Sci. Letters, I, 130, 1966. (A66-3362s) Additional evidence for the volcanic origin of lunar and Martian craters. 22. Simpson, J. F. Earth Planet. Sci. Letters, I, 132, 1966. (A66-33626) Evaporation of lava and its con23. Vonnegut, B., McConnell, R. K., Jr., Allen, R. V. densation from the vapour phase in terrestrial and lunar volcanism. Nature, 209, 44So 1966. (A66-21288) The surfaces of the Moon, Mars, and Venus. In ref. A14. 24. Menzel, D. H.

K. Luminescence and Related Transient Phenomena Excitation of lunar luminescence by solar protons. I. Anand, S. P. S., Oster, L., Sofia, S. Nature, 202, 1097, 1964. (P6s-2o96s) Luminescence of the lunar surface. Urania, 36, 166, 196s. 2. Brzostkiewicz, S. R. (A6s-27709) Apparent lunar activity: historical review. Proc. nat. 3· Burley, J., Middlehurst, B. M. Acad. Sci., 55, xoo7, 1966. (P66-28s89) Source of evolution of gas from the lunar crater Alphonsus. Nature, 20I, 4- Cohen, A. J. lOIS, 1964. (A6S-ISI41) Luminescence of meteorites. Nature, 201, 62, 1964. 5· Derham, C. J., Geake, J. E. (P64-23892) Lunar luminescence. Nature, 205, 1301, 196s. 6. Flamm, E. J., Lingenfelter, R. E. (P66-gx8o) Lunar luminescence. Nature, 204, 866, 1964. (P6s-13738; A6S-I3S3S) 7• Geake, J. E. The 1963 Aristarchus events. p. 811-5, in ref. A3. (A65-34254) 8. Greenacre, J. C. Excitation of lunar luminescence by solar flares. Nature, 9· Kopal, Z., Rackham, T. W. 20I, 239. 1964. (A64-I4I48; P64-2389I) Excitation of lunar luminescence by solar activity. Icarus, IO. Kopal, Z., Rackham, T. W. 2, 481, 1963. (P6s-7627) Luminescence on the lunar surface. Sterne und Weltraum, s, 56, 1966. I I . Kopal, Z. (A66-23943) Luminescence of the Moon and solar activity. p. 173-83 in ref. AS. (A66-35446) IZ. Kopal, Z. Mechanisms for lunar luminescence. J. geophys. I3. Ney, E. P., Woolf, N.J., Collins, R. J. Res., 71, 1787, 1966. (P66-22o7o) Some results of research on lunar luminescence. Icarus, 14. Righini, A., Jr., Rigutti, M. s. 2s8, 1966. (P66-28s87) Indication of luminescence found in the 1964 December lunar 15. Sanduleak, N., Stock, J. eclipse. Publ. astr. Soc. Pacij., 77, 237, 196s. (P66-1638s; A66-30644) Observations of lunar luminescence at visual wavelengths. Mon. Not. 16. Scarfe, C. D. R. astr. Soc., 130, 19, 196s. (P6s-33928) Luminescence caused by proton impact with special reference 17. Schutten, J., Dijk, T. Van to the lunar surface. Nature, 211, 470, 1966. (P66-32301) Lunar luminescence. Publ. astr. Soc. Pacij., 76, 112, 1964. (P64-29424) 18. Wildey, R. L.

372

COMMISSION 17

19. Geake, J. E., Walker, G. The luminescence spectra of meteorites, Geochim. Cosmochim. Acta, 30, 929, 1966. (A66-42363) 20. Moore, P. Color events on the Moon. Sky and Tel., 33, 27, 1967.

L. Lunar Environment and Atmosphere

x. Aronowitz, L., Milford, S. N. 2. 3•

4• 5· 6. 7• 8. 9·

xo. u. 12. 13. :14. :15,

Magnetic shielding of the lunar surface from the solar wind as a function of lunar magnetic moment. J. geophys. Res., 70, 227, 1965. (A65-15054) Biswas, M. M., Majumdar, D. P. Expected variations of cosmic-ray intensity on the Moon. Nuovo Cimento, 36, 1039, 1965. (P65-18541) Bowen, E. G. Lunar and planetary tails in the solar wind. J. geophys. Res., 69, 4969, 1964. (P65-15834) Cameron, A. G. W. Particle acceleration in cislunar space. Nature, 202, 785, 1964. (P65--24337) Hayakawa, S. High-energy radiations from the planets and the Moon. p. 298-3u in Space Exploration and the Solar System, New York, Academic Press, 1964. (P65--24331; A65--26915) Hayakawa, S. [Estimate of] Lunar X-rays excited by energetic terrestrial electrons, Rep. Ionosphere, Space Res. Japan, 19, 375, 1965. (P66-16386) Haymes, R. C. Juday, R. D. Detectability of lunar X-rays. Planet. Space Sci., 13. 1249, 1965. (P66-13163; A66-2o885) Hinton F. L., Taeusch, D. R. Variation of the lunar atmosphere with strength of the solar wind. J. geophys. Res., 69, 1341, 1964. (P65-15832) Michel, F. C. Interaction between the solar wind and the lunar atmosphere. Planet. Space Sci., 12, 1075, 1964. (P65-4628; A65-13344) Osborne, F. J. F., Bachynski, M.P. On a possible lunar magnetospheric configuration, J. geophys. Res., 70, 4983, 1965. (P66-6o64) Palm, A., Silver, S. On observations of lunar magnetic storms. Planet. Space Sci., 12, 649, 1964. (P64-29423) Safronov, V. S., Rouskol, E. L. The history of the lunar atmosphere and possibility of the presence of ice and organic compounds on the Moon. p. 42-53 in Proc. Xlllth Int. Astronautical Congress, Wien, Springer-Verlag, 1964. (P65-13737) Singer, S. F. Atmosphere near the Moon. Astronautical Sci., 8, 531, 1963. (P64-13916) Wehner, G. K., Kenknight, C. E., Rosenberg, D. Modification of the lunar surface by the solar-wind bombardment. Planet. Space Sci., u, 1257, 1963. (P64-7975) Vemov, S. N., et al. Measurement of the intensity of penetrating radiation on the surface of the Moon. Dokl. Akad. Nauk SSSR, :169, 1044, 1966. (A66-41410)

M. Internal Structure

x. Anderson, D. L., Kovach, R. L. 2. 3· 4•

5· 6. 7• 8.

The internal structure of the Moon and the terrestrial planets. p. 84-91 in ref. A9. (N66-31455) Caputo, M. On the shape, gravity field, and strength of the Moon. J. geophys. Res., 70, 3993, 1965. (P65-30704) Carson, D., Davidson, M., Goudas, C. L., Kopal, Z., Stoddard, L. G. Lunar profiles determined from annular solar eclipses of 1962 and 1963. Icarus, 5, 334, 1966. (P66-32295) Clegg, P. E., Bastin, J. A., Gear, A. E. Heat transfer in lunar rock. Mon. Not. R. astr. Soc., 133, 63, 1966. (A66-3726o) Davidson, M., Goudas, C. L., Kopal, Z. Lunar profiles determined from annular solar eclipses of 1962 and 1963. Boeing Document Dx-82-o470, 73 p., 1966. Eckert, W. J. On the motions of the perigee and node and the distribution of mass in the Moon. Astr. J., 70, 787, 1965. (P66-13165; A66-19352) Enzmann, R. Balance of endogenic to exogenic energy in the crust of the Moon. p. 532-542 in ref. A3. (A65-34236) Fielder, G. A case for convection in the Moon. Nature, 204, 171, 1964. (P65-18542; A65-10368)

LA LUNE

373

Convection in the Moon -a boundary condition. Geophys. J., xo, 437, I966. 9• Fielder, G. (A66-33235) The nonhomogeneity of the Moon. Icarus, 4t 2I8, I965. (P65-278oo) 10. Goudas, C. L. Note on 'Shape and Internal Structure of the Moon' by Lamar and 11. Goudas, C. L. McGann. Icarus, 5, 99, I966. (P66-I9063; A66-212Io) The figure and gravity field of the Moon. p. 27-I5I in Advances in xa. Goudas, C. L. Astronomy and Astrophysics, 4, ed. Z. Kopal. New York, Academic Press, I966. (A66-38822) The shape of the Moon as deduced from the 13. Goudas, C. L., Kopal, Z., Kopal, Z. Orbiter determination of its field. Boeing Document DI-82-o570, I966. Stress history of the Moon and of terrestrial planets. Icarus, a, 376, I963. 14. Kopal, Z. (P65-763I; A64-I6486) Radiative transport of heat in lunar and planetary interiors. Icarus, 3, 8, I964. 15. Kopal, Z. (P65-20967) Effects of thermal expansion on the moments of inertia of the Moon. Icarus, 16. Kopal, Z. 4o I66, I965. (P65-27798) Possible effects of convection on lunar moments of inertia. Icarus, 4, I73o 17. Kopal, Z. I965. (P65-27799) Internal structure of the Moon. Boeing Sci. Res. Lab. Math. Note, No. 426, 18. Kopal, Z. I965. (N66-I5700) Free oscillations of the Moon and observations by a long19. Kovach, R. L., Carr, R. E. period seismograph system. Proc. of the XIIIth Internat. Astronautical Congress, Wien, Springer-Verlag, I, I-Io, I964. (P65-I3736) Shape and internal structure of the Moon. Icarus, 5, IO, ao. Lamar, D. L., McGann, J. I966. (P66-I9062; A66-21203) Reply to 'Note on the Shape and Internal Structure of the ax. Lamar, D. L., McGann,]. Moon' by C. L. Goudas. Icarus, s, IOI, I966. (P66-I9064) Thermal history of the Moon and the development of its surface. p. 27I-273 aa. Levin, B. J. in ref. AS. (A66-35452) The structure of the Moon. Astr. Zu., 43, 6o6, I966. (P66-28579; A66-37038) a3. Levin, B. J. The structure of the Moon. p. 6I-']6 in ref. A9. (N66-3I453) 34· Levin, B.]. On the internal constitution and origin of the Moon. p. 77 in as. MacDonald, G. J. F. ref. A9. (N66-3I454) Gravity force and configuration of the Moon. Astr. Zu., 43, 1062, a6. Mikhailov, A. A. I965. (A66-I29I8) Thermal history of the Moon. Radiofizika, 9, 615, I966. a7. Ornatskaia, 0. I., Al'ber, I. I. (A66-3715I) Lunar differentiation processes. p. 47o-8o in ref. A3. (A6s-34231) ::aS. Walter, L. S. Measuring the shape of the Moon. Sky and Tel., 31, I47o I966. a9. Wildey, R. L. (A66-22964) Geophysical problems and investiga30. Zharkov, V. N., Berikashvili, V. S., Osnach, A. I. tions of the Moon (a review). Astr. Zu., 43, 622, I966. (P66-2858o) Astr. Zirk., No. 285, 1964; Nature, aoa, 12oi, I964. 3a. Levin, B. J. Proc. Lunar Meeting Roy. Soc., June 1965 (in press). 33· Levin, B. J. Icarus (in press). 34- Safronov, V. S. Dokl. Akad. Nauk SSSR, 159, No. 2, I964. 35· Majeva, S. V. Voprosy Kosmogonii, 8, 1962. 36. Koslovskaya, S. V. IZTJ. Akad. Nauk SSSR. Ser. 37· Berikashvili, V. S., Zharkov, V. N., Yanovskaya, T. B. fiziki zemli, issue 7, 9-2 I, I 96 5. N. Origin and Evolution of the Moon

Origin of the Moon. Science, x-48, 476, I965. (P66-6o65) x. Alfven, H. On the origin of the Moon. J. geophys. Res., 71, I936, I966. (P66-22o67; a. Baldwin, R. B. A66-26366)

374

COMMISSION 17

3· Hedervari, P. Instability of small-size planetary cores and the development of the Moon. Nature, 202, 378, 1964. (P64-n889) 4· MacDonald, G. J. F. Earth and Moon: past and future. Science, 145, 881, 1964. (P65-15835) On the past history of the Earth-Moon system. Icarus, 51 221, 1966. 5· Ruskol, E. L. (P66-28577) The tidal history and origin of the Earth-Moon system. Astr. Zu., 431 6. Ruskol, E. L. 829, 1966. (P66-35302) 7• Shimazu, Y. Survival time of lunar surface irregularities and viscosity distribution within the Moon. Icarus, 5, 455, 1966. (A66-3803o; P66-32299) The geology of the Moon. Sci. Amer., 2II 1 38, 1964. (P65-13739) 8. Shoemaker, E. M. 9· Urey, H. C. Meteorites and the Moon. Science, 147, 1262, 1965. (P66-6o72) IO. Urey, H. C. Chemical evidence relative to the origin of the solar system. !Mon. Not. R. astr. Soc., 131, 199, 1966. (P66-13152) II. Sorokin, N. A. Astr. Zu., 42, 1070, 1965. 12. Petrova, G. G. Diploma work, Physical Dept., Moscow University, 1965. 13. Ruskol, E. L. Izv. Akad. Nauk SSSR, ser. geofiz., issue 2, 216-22, 1963.

19. COMMISSION DE LA ROTATION DE LA TERRE PRESIDENT: Dr B. Guinot, Observatoire de Paris, 61 avenue de l'Observatoire, Paris-14e, France. VICE-PRESIDENT: Dr P. J. Melchior, Observatoire Royal de Belgique, 3, avenue Circulaire, Uccle-Bruxelles 18, Belgique. CoMITE D'ORGANISATION: G. Cecchini, E. P. Fedorov, W. Markowitz, H. M. Smith. MEMBRES: Abraham, Aksentjeva, Atkinson, Billaud, Bonanomi, Brkic, Buchar, Chudovicheva, Danjon t, Demetrescu, Dramba, Enslin, Essen, Fichera, Fleckenstein, Gama, Hall (R. G.), Hers, Iijima, Jeffreys, Kalmykov, Koebcke, Kulikov (K. A.), Lagrula, Lederle, Levallois, Mikhailov, Miyadi, Nicolini, Okuda, Opalski, Orlov (B. A.), Orte, Pavlov (N. N.), Popov, Postoiev, Randic, Rice, Romanskaya, Sakharov, Scheepmaker, Sevarlic, Stoyko (A.), Stoyko (N.), Sugawa, Takagi, Tanner, Tardi, Torao, Tsao, Vicente, Witkowski, Young, Yumi. I.

MESURES DE LA LATITUDE ET DU TEMPS UNIVERSEL

(a) Observations astronomiques en cours Nous donnons ci-dessous Ia liste des stations ayant mesure l'heure et Ia latitude durant Ia periode 1963 a 1966. La station est designee par le nom de Ia ville ou elle se trouve. On donne les coordonnees approximatives. La colonne 'instrument' designe !'instrument en service a Ia fin de 1!}66. Les abreviations suivantes sont utilisees: IP instrument meridien des passages IP Ph : instrument meridien des passages avec enregistrement photoelectrique PZT : lunette photographique zenithale. LZV : lunette zenithale visuelle des latitudes. La notation xfy donne l'ouverture x de l'objectif et Ia longueur focale y, en em. Dans Ia colonne 'grandeur mesuree', q> indique Ia latitude, T, le temps universe!. Dans la colonne 'renseignements divers', on donne des indications sur la continuite des mesures entreprises et des references d'ouvrages ou ont ete publies les resultats detailles.

Station Alger

+37o, -oh 12m

Belgrade +45°, -

Instrument Astrolabe (OPL 8) LZV

Ih

22m

(II/129)

IP

Grandeur mesuree T

cp,

Renseignements divers Depuis 1958, programme inchange. Publication detaillee en preparation. Depuis I 949 Publ.: Bull. Obs. astr. Belgrade. Publ.: jusqu'a 1960: Bull. Obs. astr. Belgrade.

cp

T

(10/100) Besan~on

+47°, -oh 24m

HH

Astrolabe (OPL 31)

cp,

T

375

De 1959 a 1960, astrolabe prototype. Depuis janvier 1961, astrolabe OPL 31, suivant programme invariable. Publ.: pour 1959-60, Ann. Obs. Besanc:on, 6, fasc. 1 et 2.

COMMISSION 19

376 Station

Instrument

Grandeur mesuree

Renseignements divers Publ.: 196o-63, Observations with zenith telescopes during the period 1960-63. Moscow, 1964.

Blagovestchensk +5oo, -8h 30m

LZV (ZTL 180)

'P

Borowa-Gora + 52°,- Ih 24m

IP Ph (Zeiss 10/1oo)

T

Boroviec +52o, -Ih 8m

2 IP (Zeiss 10/100) zLZV

T

Bucarest +44°, -Ih 44m

IP Zeiss

T

Depuis 1957. Pub I.: Bulletin du Service de l'Heure de l'Obs. Des mesures de latitude ont etc effectuees de 1959 a 1961.

Buenos Aires (Inst. geogr.) -35°, +3h 53m

IP

T

Publ.: Bulletin mensuel 'Senales horarias radiotelegraficas'.

T

Publ.: Bulletin mensuel de 'Observatorio naval de Buenos Aires, Servicio de Hidrografia Naval' Note: Installation d'un PZT en cours, ala meme latitude que Mount Stromlo.

IP

Publ.: Astr. Lat. st. of the polish Academy of Sciences, Borowiec. Circular.

'P

Buenos Aires (Obs. nav.) - 35°> + 3h 53m

2

Carloforte +39°, -oh 33m

LZV

Dresde + 5Io, -oh 55m

LZV (Zeiss 10/100)

Gorki + 560, -zh 56m

LZV

Publ.: Voir Blagovestchensk.

Gaithersbourg +39o, +5h 9m

LZV

Depuis 1900. Station du SIMP

Greenwich (Herstmonceux) +51o, -oh 1m

PZT

Depuis 1900. Station du SIMP. Publ.: Zirkular, Technische Universitat Dresden, Lohrmann-Institut.

rp, T

I.

z. 3·

Hambourg (Inst. hydrog.) +54°, -oh 40m

PZT

Irkoutsk (Obs.) + 52°, -6h 57m

IP Ph

"'' T

I. 2.

LZV (ZTL 18o)

T

La latitude a etc mesuree de 19II a 1940 avec la lunette zenithale flott. Cookson. L'astrolabe OPL 9 a etc utilise de 1959 a 1963. PubI.: R. Obs. Bull., no. 92. Le PZT fonctionne depuis 1955. Publ.: R. Obs. Bull., tous les 3 mois. Des instruments des passages ont etc utilises de 1955 a 1958. Le PZT est en service depuis 1958. Publ.: 1957-58, Breitbestimmungen (Circ.). 1959-61, Deutsches hydrog. Zeitung. 1961 ... Time Service Bulletins.

Publ.: Jetalonnoe Vremja .•• , Institut de mesures physico-techniques et radiotechniques (Moscou), mensuel. Voir Blagovestchensk.

ROTATION DE LA TERRE Station Irkoutsk (Mesures) + 52o, -6h 57m Kasan (Obs. Engelhardt) +s6o, -Jh ISm

Instrument 2 astrolabes (OPL 22 et 26) IP } IPPh

Grandeur mesuree

T

7',

377

Renseignements divers Publ. : Voir Blagovestchensk et Irkoutsk (Obs.).

T

Publ. : voir Blagovestchensk.

LZV (ZTL 180)

Kharkov +soo, -2h 25m

IP Ph

T

Kitab +39°, _4h 28m

LZV

rp

Depuis 1928. Station du SIMP. (a remplace Ia station de Tchardjui).

La Plata -35°. +3h 52m

LZV IP

rp

T

Depuis 1929. Publ.: Boletin Horario, Observatorio astronomico de Ia Universidad Nacional.

LeCap -34°, - Ih 14m

Astrolabe (OPL 9)

Leningrad (Obs. astr.) +6o 0 , -2h 1m

IPPh

T

Publ.: voir Irkoutsk (Obs.).

Leningrad (Mesures) +6o 0 , -2h Im

IP IP Ph

T

Publ.: voir Irkoutsk (Obs.).

Milan +45°, -oh 37m

IP Obs. zenithales

Mizusawa +39°. -9h 25m

Mont Pourpre +32°, -7h ssm

rp,

Publ.: voir Irkoutsk (Obs.)

T

Depuis 1961. Publ.: Astronomical Observatory of Milan. Circular no. 18. Publ.: Circulars. Note: L'installation d'un astrolabe OPL est prevue.

IP (Askania xo/roo)

T

LZV LZ flottante

rp rp

PZT

rp,

T

Astrolabe (OPL 34)

rp,

T

IP

Depuis 1965. Publ.: Mon. Not. astr. Soc. Sth. Ajr. (vol. XXV, 1966, pour avril 196s-juillet 1966).

T

Depuis 19oo. Station SIMP. Depuis 1940 Publ.: (1) IGY and IGC Data on Latitude and Longitude, Part I, Sc. (Council of Japan) Depuis 1956 (2) Publ. of the Int. Lat. Obs. ofMizusawa (3) Annual Reports of IPMS Depuis 1966 (4) Mizusawa Time Service Bull.

COMMISSION 19

378 Instrument

Grandeur mesuree

Mount Stromlo (Canberra) -350. -9h 56m

PZT

cp, T

Depuis 1959. Publ.: Temps, Mount Stromlo Bulletins TS1D, jusqu'a 1961, puis Bulletins B. Note: mesures de T.u. faites auparavant avec IP.

Moscou (Obs. astr.) +56o, -zh 30m

IPPh

T

PZT

cp, T

La latitude a ete mesuree egalement, de 1958 a 1964 avec un instrument ZTL I80 (periode de 6 ans). Publ.: voir Blagovestchensk et Irkoutsk (Obs.).

IP Ph

T

Astrolabe (OPL 23)

cp, T

Neuchatel +47o, -oh zSm

PZT

cp, T

Nikolaiev +47o, -zh 8m

IP Ph

T

Publ.: voir lrkoutsk (Obs.).

T

Publ.: voir Irkoutsk (Obs.).

Station

Moscou (Mesures) +56o, -zh 3Im

Novossibirsk (Mesures) + 55°. - 5h 32m Ottawa +45°. +5h 3m

2

IP

2 Astrolabes (OPL 25 et 27) PZT

Renseignements divers

Publ.: voir Irkoutsk (Obs.).

Depuis 1956. Publ.: Bulletins A et B de l'Obs. de Neuchatel. Note: Des observations de ,, T ont ete faites avec un astrolabe OPL, de 1958 a 1965.

cp, T

"' T

Astrolabe (OPL 01, puis 35)

cp, T

Pecny + 50o, -oh 59m

IP Circum zenithol Nusl. Fric LZV

T

Poltava +5oo, -zh ISm

LZV Astrolabe (OPL)

tp

Prague + 500, -oh 58m

IP

T

cp

Depuis 1952. Publ.: Time and Latitude Bull. of the Dominion Obs. (nouvelle reduction, a partir de 1956, disponible sur demande). Depuis 1956. Publ.: Notes et Informations, fasc. 2, 3, 4, 5, 7, 13, 19, 29, jusqu'a 1964. La suite sera publiee dans le Journal des Observateurs, Marseille. Publ. : Bulletins de Ia Station de l'Heure a Prague. Academie tchecoslovaque des Sciences. Publ. : voir Blagovestchensk.

Publ.: Voir ci-dessus pour Pecny.

ROTATION DE LA TERRE Station

Instrument

Potsdam + 52°, -oh 52m

3 IP Astrolabe (OPL 1o)

Poulkovo +6o 0, -2h xm

IP Ph LZV (ZTF 135 et ZTL x8o)

Grandeur mesuree

Renseignements divers

T

Astrolabe, depuis 1957. Publ.: 1957-62, Arbeiten aus dem Geodlitischen Institut Potsdam, Nr I, 4 und 10. Depuis 1962: Astronomische Zeit-und Breitenbestimmungen, Empfangzeiten von Zeitsignalen (Bulletin mensuel).

T

Pub!.: vmr Blagovestchensk et Irkoutsk (Obs.).

cp, T

2

Astrolabe (OPL 13)

379

cp,

T

Depuis 1963. Publ.: prevue en 1967, par l'Obs. de Quito.

PZT

cp, T

Astrolabe (OPL)

cp, T

Riga + 57°, - xh 36m

IP Ph

T

Publ.: voir Irkoutsk (Obs.).

Rio de Janeiro -23°, +2h 53m

IP

T

Pub!.: Bulletin horaire mensuel.

Saint-Michel +44°, -oh 23m

Astrolabe (OPL 12)

cp, T

Depuis 1963. Publ.: prevue en 1967, J. Observateurs, Marseille.

San Fernando +360, +oh 25m

IP

T

Publ.: Bol. del Obs. de San Fernando, Servicio de Hora (mensuel). Note: Installation d'un astrolabe OPL en cours.

Santiago du Chili -33°, -4h 42m

Astrolabe (OPL 3)

cp, T

Depuis 1965. Auparavant, depuis 1957, observations de T sur IP. Publ.: Bull. horaires de l'Obs. nat. de Santiago du Chili.

Richmond +260, + 5h 22m

Depuis 1949· Publ.: voir Washington. Depuis 1964.

Tachkent +41°, -4h 37m

IP IP Ph

T

Tientsin +39°, -7h 49m

LZV

'I'

Note: sur le parallele des stations du SIMP.

Tokyo +360, _9h ISm

PZT

cp, T

Depuis 1955. Publ.: IGY Data on Long. and Lat. (Science Council of Japan). Post IGY Data on Long. and Lat. (Science Council of Japan). Time Service Bull. Time and Lat. Bull.

Turku +6oo, -lh 29m

LZV

'I'

Depuis 1960. Publ.: 1960-63. Annales Academiae Scientiarum Fennicae, 1963, 71.

Publ.: voir Irkoutsk (Obs.).

COMMISSION 19

380

Station

Instrument

Grandeur mesuree

Renseignements divers

Uccle

2 IP Astrolabe (OPL 7)

cp, T

T

Astrolabe, depuis 1962 (1965 pour cp). Publ.: pour T: Bull. horaires de l'Obs. Royal de Belgique.

Ukiah

LZV

'P

Depuis 1900. Station du SIMP.

IP LZV

T

+ 52°, - Ih 24m

Washington

PZT

cp, T

+5Io, -oh I7m

+39o, +8h 13m

Varsovie

'P

+39o, +5h gm

Zikawei

+3Io, -8h 6m

2

IP Ph

Astrolabe (OPL)

De 1959 a 1963. Reprise prevue. Depuis 1959. Publ. : Publ. of the chair of geodetic Astronomy of the Warsaw techn. Univ., no. 4· Circulaires de l'Obs. no. I a 34· Depuis 1915, pour cp. Publ.: cp, Astr. J., IIIO, II3o, II4I, II44, II47, II50, II54, II59, de 1939 a 45• T, U.S. Naval Obs. Time Signal Bulletin.

T cp, T

(b) Projets en cours de realisation Plusieurs projets tendent a corriger Ia mauvaise repartition geographique des instruments et a organiser des chaines d'instruments a latitude egale qui donneront des informations sur Ia derive des continents et du pole.

La lunette zenithale photographique (PZT) d'Ottawa doit etre placee aproximite de Calgary (Alberta) sur le parallele de celle de Herstmonceux. Les programmes seront conjugues. Un nouveau PZT sera installe a Ottawa (nouveau site de l'Observatoire). De meme un nouveau PZT installe a La Plata sera conjugue avec celui de Mount Stromlo. L'Observatoire de Besan9on envisage de transferer son astrolabe aIa Terre de Feu (cp = - 55°), par accord avec le service hydrographique de Ia marine d' Argentine. Des mesures de temps et latitude ont ete effectuees avec un astrolabe OPL, a Sao Paulo (cp = -23°). Le transfert de !'instrument plus au nord devrait permettre d'avoir de meilleures conditions atmospheriques et il est prevu. Les mesures de latitude doivent etre entreprises a Sopron (Hongrie), avec une lunette zenithale visuelle. On note, avec Ia plus grande satisfaction, que Ia situation des mesures dans !'hemisphere austral s'ameliore considerablement, grace aux efforts faits par plusieurs observatoires d' Amerique du Sud et par Ia mise en service d'un astrolabe au Cap. Cependant, I' installation de nouvelles stations dans }'hemisphere austral reste souhaitable, afin d'egaliser Ia repartition en longitude. II. SERVICE INTERNATIONAL DU MOUVEMENT POLAIRE

(a) Rapport du Directeur (DrS. Yumi) The work of the International Polar Motion Service has been carried on smoothly from the beginning of 1962 through this period.

ROTATION DE LA TERRE

3Sl

During the past three years, eight stations participated in the service and 38 stations in 21 countries are collaborating in the IPMS at present. They are: Alger, Belgrade, Besant;on, Blagovestchensk, Borowiec, Carloforte, Cape, Dresden, Engelhardt, Gaithersburg, Gorky, Greenwich, Hamburg, Irkutsk, Kitab (2 instr.), La Plata, Milan, Mizusawa (3 instr.), Mt Stromlo, Neuchatel, Ottawa, Paris, Pecny, Poltava (2 instr.), Potsdam, Prague, Pulkovo, Quito, Richmond, San-Fernando, Santiago du Chili (2 instr.), Sao Paulo, Tokyo, Uccle (2 instr.), Ukiah, U.S.S.R. (Mean Observatory), Warsaw and Washington. The collected data of all the collaborating stations were arranged and studied during this period so that they could contribute to the determination of the pole's coordinates, the results of which will be published in the next three year period. Preliminary values of the instantaneous pole referred to the new system 190o-o5 of the ILS, calculated using only the results of the five ILS stations on the northern parallel of 39° 8', and the preliminary summaries of the results of latitude observations made at the collaborating stations were published in the 'Monthly Notes of the IPMS' as a rapid service. 'Annual Report of the IPMS' was prepared to give the full data of the collaborating stations, coordinates of the pole, method of reduction and any other remarks which are considered to be necessary. Three volumes were published for the years 1962, 1963 and 1964 by this time. No time data but only the latitude data were given in them. Coordinates of the instantaneous pole referred to the new system 19oo-os (Unit: o?oox) U.T.

X

y

U.T.

X

y

U.T.

I962·oo ·os '10 '15 '20 ·zs '30 '35 '40 '45 ·so '55 ·6o ·6s '70 '75 ·So ·ss '90 '95 1963'00 ·os '10 'IS '20 ·zs '30 '35 '40 '45

9 + s + 27 + 47 + 71 + 95 +IZO +144 +16z +173 +I7I +157 +IzS + 94 + s6 + I7 19 54 S6 -IIO -1ZI -II9 -IOS 76 3s + 9 + 70 +134 +191 +Z39

+297 +309 +314 +312 +304 +Z90 +Z71 +z46 +Z14 +175 +13Z + 9Z + 6S + 6o + 67 + S3 +104 +1zS +I6o +zoo +z4S +Z95 +3Z9 +356 +376 +3SS +JS7 +375 +349 +307

I963·so '55 ·6o ·6s '70 '75 ·So ·ss '90 '95 1964'00 ·os 'IO 'IS ·zo ·zs '30 '35 '40 '45 ·so ·ss ·6o ·6s '70 '75 ·So ·Ss '90 '95

+274 +301 +2S1 +237 +176 +112 + 4S - II - 69 -1ZZ -I7I -zo6 -I94 -I69 -I39 -IOI - 55 + 4 + 74 +164 +214 +240 +Z41 +Z39 +z55 +250 +ZI9 +I6I + 99 + 4Z

+251 +193 +139 + 91 + 46 + s zo + 5 + 41 + 7S +120 +I6S +230 +Z94 +353 +4IZ +455 +467 +459 +436 +394 +339 +275 +2I9 +16S +IZ3 + ss + 6o + 46 + 43

I96s·oo ·os '10 'IS '20 ·zs '30 '35 '40 '45 ·so '55 ·6o ·6s '70 '75 ·So ·Ss '90 '95 1966·oo ·os 'IO 'IS '20 'Z5 '30 '35 '40 '45

X

y

- IS + 49 + 6S - 73 +101 -125 -161 +154 -1S3 +223 +Z91 -194 -193 +337 -175 +374 -I34 +409 - 7Z +435 + z +444 + 74 +434 +126 +402 +I66 +354 +zoo +307 +261 +221 +zz2 +Z29 +1S7 +2Z3 +195 +157 +I3Z +I37 +ns + 71 +I03 + 30 + 9S 5 + 9S 37 +Ios 64 ss +IZO -Io6 +145 +17S -II7 (- IZO) ( +ZI3) ( -II4) ( +zsz)

382

COMMISSION 19

A total of 42 255 observations were made at the five ILS stations- Mizusawa, Kitab, Carloforte, Gaithersburg and Ukiah during the period from 6 August 1963 to 5 August 1966. The coordinates of the instantaneous pole, derived from these observations are shown in the following table together with the revised values for the period 1962·oo-1963 ·55· The values for the years 1962-64 are referred to the Annual Report of the IPMS and those for 1965-66 are to the Monthly Notes of the IPMS. Scientific Council of the Service proposed at its meeting of Berkeley, U.S.A. in 1963 that the star pairs of the current observation programme for the five ILS stations which was adopted at 1955·o were desirable to be improved and the new ones would be put into practice from 1967·0 on for at least 12 years. New programme and its star pairs were prepared by the Central Bureau and were approved by the majority of the members of the Council and the ILS stations during I 966. There is no change in observation programme- three groups a day- but combinations of stars or of star pairs in a group are changed. (b) Reunions du conseil scientifique du SIMP Ce conseil (B. Guinot, president, E. Fedorov, P. Melchior, W. Markowitz, S. Yumi) s'est reuni en aout 1964, aout 1965. Il a eu a traiter de la publication des resultats dans les Monthly Notes of the IPMS et du renouvellement du programme des stations internationales. III. SERVICE INTERNATIONAL DES LATITUDES

(a) Periode I94I·o-I948·9 Le Professeur T. Nicolini qui s'est charge de la reduction des observations faites durant cette periode sous la direction de Camera, annonce que son travail sera acheve avant la fin de l'annee 1966. Pour attenuer les incertitudes sur l'inconnue x, il a fallu faire appel aux series discontinues de Kitab et Pino Torinese. Un rapport plus detaille est donne en annexe au present rapport, page 390. (b) Periode I949·r:ri!)6I·9 Le Professeur G. Cecchini a etabli le rapport suivant (traduction). 'Comme l'on sait, apres la reduction provisoire des observations de latitude accomplies dans les stations boreales internationales de Mizusawa, Kitab, Carloforte, Gaithersburg et Ukiah, au cours des six annees 1949-54 et des six annees 1955-61 (ces dernieres sur un nouveau programme d'observations), on a entrepris l'etude definitive de ces memes observations, au nombre de 148 350; etude rendue necessaire pour les raisons suivantes. Avant tout, les calculs provisoires, bien qu'effectues avec le maximum de soin et d'attention, necessitent un examen approfondi, afin d'eliminer, chaque fois que possible, l'erreur systematique loin d'etre negligeable qui resulte de l'emploi de tours de vis et de coefficients thermiques constants pour chacune des stations: !'important materiel d'observations, sur, a demontre incontestablement la realite des remarquables variations du tour de vis, quand, par les approximations successives, on utilise les reductions d'un meme couple d'etoiles ala declinaison moyenne du groupe auquel il appartient, compte tenu du fait que ces reductions devraient donner des resultats identiques pour toutes les stations. 'Cependant la bonne qualite des resultats obenus, pour le but identique s'avere demontree, particulierement au cours de la deuxieme periode, en admettant que les corrections de tour de vis ont ete traitees separement pour les groupes du soir, intermediaire et du matin. 'En outre, on a du tenir compte de petits termes negliges dans les reductions provisoires et, particulierement, du fait que ces memes observations de latitude, assignent la valeur 20'! so a la constante de !'aberration, au lieu de la valeur usuelle 2o'!47, ceci en accord avec les resultats d'autres auteurs, a partir d'observations d'un autre type. Ceci, evidemment, constitue un

ROTATION DE LA TERRE

383

resultat d'une remarquable valeur, encore que la complexite du phenomene de la variation de la latitude terrestre soit telle (specialement par !'intervention de phenomenes locaux si difficiles a preciser et impossibles a eliminer) que les resultats obtenus puissent bien difficilement etre consideres comme entierement exempts d' erreurs systematiques. 'L'elaboration definitive de toutle materiel observe demandera encore beaucoup de temps; mais, juqu'a present, on a pu constater que les changements, bien que notables, apportes aux constantes de reduction, n'influeraient pas beaucoup sur la polhodie de toute la periode I949-6I, telle qu'elle a ete presentee aux Assemblees Generales de l'UAI et de l'UGGI. 'La valeur de la reduction definitive en cours, consistera principalement a permettre !'usage, pour des recherches ulterieures, des resultats obtenus dans un systeme le plus homogene possible et d'ou l'on pourra deduire des conclusions dignes de foi.' (c) Remerciements

Nous tenons a remercier les Professeurs T. Nicolini et G. Cecchini, ainsi que la Commission Geodesique Italienne pour la poursuite de cet important travail. IV. SERVICE INTERNATIONAL RAPIDE DES LATITUDES {SIR)

Madame A. Stoyko et N. Stoyko ont poursuivi le travail du SIRjusqu'en avril I965. Ensuite, la publication rapide des coordonnees du pole et des corrections de longitude deduites a ete consideree comme faisant partie du travail du Bureau International de l'Heure. Actuellement {I966), les coordonnees du pole sont encore deduites des mesures de latitude seulement, par Melle M. Feissel et B. Guinot, a partir des donnees d'une trentaine de stations. Les calculs et !'edition des circulaires ont ete automatises. On commence a utiliser I' ensemble des mesures de temps et de latitude pour calculer simultanement les coordonnees du pole et le temps universe! T.v. 1. Voir ace sujet le rapport du BIH ala Commission 31. Une publication detaillee de ces methodes est en preparation. On donnera ci-apres quelques resultats obtenus. V. TRAVAUX DE RECHERCHE SUR LA ROTATION DE LA TERRE

(a) Resultats d'ensemble des observations pour la periode 1962-66

La Figure I montre la polhodie deduite des observations aux stations du SIMP, la Figure les fluctuations de la dun~e du jour.

2,

(b) Instruments Il n'est pas apparu d'instruments d'un type nouveau, mais l'equipement a fait l'objet d'ameliorations techniques. L'emploi de chronographes totalisateurs ou perforateurs, de machines automatiques a mesurer les plaques se generalise. (c) Erreurs d' observation Pour les mesures de la latitude, la qualite des divers instruments reste un objet d'etude. Glagoleva et d'autres auteurs d'U.R.S.S. ont etudie la repartition spectrale des erreurs d'observations. Les instruments recents: PZT' astrolabes et lunettes zenithales modernes (ZTL I So) donnent, dans !'ensemble, des resultats meilleurs que les anciennes zenithales, mais cette amelioration est assez modeste. Par contre, il y a des differences marquees dans la qualite des mesures de l'heure. Les instruments ou le zenith est uniquement defini optiquement par reflexion sur un bain de mercure (astrolabes, PZT) donnent des resultats d'une meilleure precision interne et affectes d'erreurs systematiques plus petites ou plus stables que les instruments des passages classiques.

384

COMMISSION 19

0

X

~v+o:4

Fig.

1.

+o·:3

+o;·2

+o';J

o

Polhodie d'apres le SIMP.

Fig. 2. Variation de Ia dun~e du jour de 1963·0 a 1966·7. L'echelle de gauche montre l'exces de Ia duree du jour sur la duree de 86 400 secondes atomiques (apres correction de l'effet saisonnier); l'echelle de droite, le decalage relatif de la frequence nominale qu'il faudrait adopter pour que le temps atomique suive T.u. 2. Les petits cercles representent les moyennes annuelles. Les astrolabes A. Danjon ont fait l'objet d'etudes quant aux deplacements du plan focal en fonction de la temperature par Gozhy et Slavinskaja. Scheepmaker a etudie les erreurs personnelles a l'Observatoire de Quito. Les ecarts personnels des resultats peuvent atteindre o':I en latitude, 10 ms en temps.

Les PZT montrent parfois des erreurs de fermeture anormales en latitude: a Hambourg et En particulier a Herstmonceux, il est necessaire d'apporter une correction

a Herstmonceux.

ROTATION DE LA TERRE

385

empirique de o'!o6 sind (d partie decimale de la date julienne) aux latitudes observees: l'origine de cette erreur parait etre instrumentale. Une limitation ala precision des mesures est dans la turbulence atmospherique. Les memes instruments places dans des sites differents donnent des resultats d'une valeur parfois tres variable, comme l'ont montre le transport du PZT d'Ottawa et des transferts d'astrolabes, suivis par les memes observateurs. Les effets de salle ont ete etudies par Goto. Les refractions a basse altitude par Goto et al. L'effet du vent et des anomalies de la refraction a ete etudie par Mischenko. Tuterev a trouve une correlation entre la refraction calculee en tenant compte de l'inclinaison des couches d'air et les resultats de mesures de temps et latitude a Herstmonceux, Poulkovo et Tokyo. (d) Programmes d'observation, reduction des observations

La methode des observations en chaine restant d'un emploi general pour la reduction des observations a un systeme homogene, dans les stations independantes, a fait l'objet de travaux de Thomas et de Enslin, qui recherchent un programme optimal, compte tenu des conditions meteorologiques. Ala methode classique des paires de Talcott, Kolaczek et Bieniewski ont substitue I' observation de paires de groupes d'etoiles. Plusieurs observatoires ont du modifier leurs programmes d'observations, a cause de la precession. Le SIMP a prepare un nouveau programme de 12 ans, a mettre en service en janvier 1967. Outre les coordinations de programmes mentionnees ci-dessus en 1 (b), des observations simultanees des memes etoiles avec les lunettes zenithales flottante et visuelle de Mizusawa sont en cours. Teleki et Sevarlic ont compare, par des observations simultanees, l'ancien et le nouveau programme du service des latitudes de Belgrade. Fichera propose une coordination des mesures de l'heure pour les instruments des passages a des latitudes voisines. Les methodes de reduction des observations au PZT et a !'astrolabe de Herstmonceux ont ete exposees dans deux importants memoires de Thomas. Takagi a etudie le role des erreurs de positionnement du PZT. La constante d'echelle et le pas de vis des lunettes zenithales ont fait l'objet de nombreux travaux. Le large champ des lunettes zenithales ZTL ISO permet d'observer des paires d'etoiles avec des differences de declinaison de I? 5; par suite 1' echelle et son coefficient thermique sont determines avec une grande precision relative et les resultats ne sont pratiquement pas affectes par les erreurs des declinaisons (Gurstein, Rykhlova et Prodan). N. A. Popov a discute une nouvelle methode pour obtenir la constante d'echelle a partir des memes observations d'etoiles zenithales. (e) Revision des catalogues et nouvelles reductions des series de mesure de temps et latitude Poulkovo: Une nouvelle reduction des observations faites avec Ia lunette ZTF 135, de 1948 a 1960, a ete achevee (avec la nouvelle valeur de Ia constante de I' aberration). Mount Stromlo: Les resultats du PZT ont ete reduits a un systeme unique, depuis 1959. Tokyo: Des declinaisons corrigees sont utilisees depuis 1966 pour le PZT, mais les ascensions droites n'ont pas ete changees. Washington: Toutes les observations de PZT, depuis I9I5 sont en cours de revision, afin d'ameliorer les positions des etoiles.

386

COMMISSION 19

Ottawa: Les resultats de la periode 1956·o-x961 ·o ont ete rendus homogenes avec les suivants, par nouvelle mesure des plaques et nouvelle reduction (conclusion a paraitre dans le Dominion Obs. Bull.). Rappelons que les programmes d'astrolabe peuvent etre conserves invariables et qu'ils sont par consequent homogenes quand ils sont exprimes dans le systeme du catalogue de reference (FK4). Cependant certaines stations font usage de corrections de groupe qui sont sujettes a revision. La grande precision avec laquelle la constante d'echelle des ZTL x8o est mesuree permet d'utiliser ces lunettes pour determiner les differences de declinaison des paires d'echelle du SIMP. Des observations, pour ce but, ont ete entreprises par quelques observatoires d'U.R.S.S. Les positions et mouvements prop res des etoiles du SIMP (ou SIL) ont ete obtenus par Major; !'accord est bon avec les resultats de Mizusawa, Ukiah, Carloforte, de 1906 a 1935. Les mesures de temps et de latitude sont utilisees pour ameliorer le catalogue fondamental (voir Commission 8). Plusieurs catalogues bases sur les mesures d'heure en U.R.S.S. ont ete publies par Afanasyeva et al., Vasiliev, Chelomlitko, Michenko, Yasevich, Blinov; un catalogue de compilation en est deduit par l'Observatoire de Poulkovo (a paraltre a la fin de 1966); il doit com prendre 8oo etoiles et repose sur plus de I 50 ooo observations.

(f) Calcul de la polhodie La simple consideration de l'erreur interne des mesures ne suffit pas a fixer le poids a introduire dans les calculs, comme l'ont montre plusieurs auteurs d'U.R.S.S. Une nouvelle methode d'estimation des poids a ete decrite par Fedorov et Korsun. Mme A. Stoyko a acheve la determination de la polhodie, pendant l'AGI et la CIG a partir de 50 instruments. Pour cette periode, elle a calcule le terme non polaire Z, a partir des 38 meilleures series d'observations: la demi-amplitude de ce terme (o'to38) et sa phase sont en parfait accord avec celles deduites de 6o annees d'observations du SIL. Z ne depend pas, en moyenne de Ia latitude, ni du type d'instrument. Mais quelques stations donnent des valeurs anormales. B. Guinot et M. Feissel ont determine le mouvement du pole de 1964·0 a 1966·5 a partir de l'ensemble des mesures de temps et de latitude de plus de 6o stations. Dans ce premier travail, les mesures brutes sont utilisees, telles qu'elles sont transmises par les observatoires. L'etude des residus est en cours. Bien que les resultats de chaque station n'aient pas ete lisses, les coordonnees du pole calculees pour chaque xj2o d'annee varient d'une fac;on tres reguliere (Figure 3). La polhodie differe sensiblement de celle obtenue par le SIMP; son aspect general est plus proche du cercle. La solution essayee avec le terme Z des latitudes, donne a Z une xjz amplitude de o~o2. La phase est differente de celle trouvee a partir des mesures de latitude seules. (g) Analyses des mesures Le probleme general de !'analyse des series temporelles a ete traite par Jeffreys dans Ia derniere edition de son ouvrage 'Theory of Probability'. La methode d'Orlov, pour separer les composantes du mouvement du pole a ete generalisee par Iijima qui l'a etendue a toutes les periodicites pratiquement utiles. Le spectre du mouvement polaire a ete etudie par des auteurs d'U.R.S.S. Pour Ia periode 1891'5 a 1962·0, Yashkov, en plus du terme annuel et du terme de Chandler a trouve des termes a periodes de x·x7, x·238 et 1·245 an. Une conclusion differente a ete atteinte par Fedorov et Yatsin, qui attribuent ces periodes multiples a de considerables variations de phase et d'amplitude de !'oscillation chandlerienne. Le spectre typique de la variation de la latitude montre une decroissance continue de la densite spectrale avec la frequence et des sommets pour certaines frequences; ces traits sont communs a toutes les series d'observations (Glagoleva,

ROTATION DE LA TERRE

387

Fig. 3· Polhodie d'apres les mesures de temps et de latitude faites en 61 stations. L'origine est arbitraire. Les points sont obtenus sans lissage. Yatskiv, Panchenko et Korba). Des termes periodiques non polaires sont presents dans les observations de latitude; Major attribue certains d'entre eux a des termes incorrects de Ia nutation astronomique et de Ia nutation diume, l'origine des autres est encore obscure. N. A. Popov a continue ses etudes de Ia nutation diume. Kulagin et Kovbasyuk ont trouve dans les observations de latitude a Gorki les termes diume, semi-annuel et semi-mensuel de Ia nutation, avec des demi-amplitudes de 0~039, 0~039 et 0~015. Nesterov s'est aussi occupe du terme semiannuel. Rusu a annonce !'existence d'un terme a periode de o·75 an. Sugawa a etudie les effets lunaires de man!e sur les observations faites a Mizusawa, de 1935 a 1961 et Mlle Debarbat, sur celles faites a Paris (temps et latitude) de 1956'5 a 1963 ·o. La variabilite de la periode de Chandler a ete a nouveau mise en evidence par les travaux ·de Iijima; d'apres cet auteur I' ellipse du mouvement annuel du pole varie considerablement et par suite les positions du pole d'inertie qu'il en deduit varient d'une annee a l'autre; ces variations sont attribuees a des anomalies meteorologiques a l'echelle mondiale. Les coordonnees du pole d'inertie ont ete egalement calculees par Dramba et Stanila. On n'a pratiquement pas progresse dans la determination experimentale des derives du pole. Le taux de variation de la latitude moyenne a Paris, de 1956·6 a 1962·7 trouve par Guinot a ete confirme par Okuda et Sugawa, d'apres les observations de Mizusawa et Tientsin; a Paris,

= 17·85 - 2·97log P, which agrees in slope with that found in the LMC by the Herstmonceux group. The colors are systematically bluer than Arp's SMC cepheids. Th~ derived distances are 61 kpc (SMC) and 50 kpc (LMC). Dickens (15) reports 2-color photometry of 10 cepheids in Herstmonceux Field 2. The P-L relation was discussed at the Herstmonceux Conference on Stellar Evolution (63). Wesselink (57, 58) has published results for 45 faint SMC variables, including five with periods shorter than one day, and magnitudes based on measures with objective grating. The predominance of periods less than two days in this rich region is striking. Hodge and Wright (35) have discovered 51 new variables in the LMC, while eight new variables in the wing of the SMC are reported by A. D. Andrews (3). The Gaposchkins continue their studies of Harvard variables based on the Arp SMC sequence (24, 25, 26). They find that variables with sinusoidal light-curves (M- m > o·3) define a P- L relation lying m higher than the P- L relation for normal cephoids (24). The general relationship of form of light-curve and period is similar to that found in the galaxy. Mrs Gaposchkin (23) finds the slope of the P - L relation systematically steeper at the bright end than the faint. S. Gaposchkin (28) finds that at any given period the amplitude of a SMC cepheid tends to increase with maximum brightness. He has also studied 33 eclipsing variables in the SMC (27); he finds none brighter than (Mpg) while relative to the known SMC cepheids they appear to be five times rarer than in the Galaxy. Gascoigne (48) discusses cepheids and stellar birth-rates and stresses the rarity of Cloud cepheids in clusters and associations. Arp's SMC sequence is being re-observed at Boyden (C. J. Butler) and Radcliffe (P. J. Andrews) Observatories. At Boyden cepheids in two LMC fields and one SMC field are being observed by four-color photometry to 18th magnitude (4). Van Genderen (Leiden) is studying SMC cepheids on the basis of plates taken by Arp. The LMC cepheid HV 953 has been studied over a 6o year span by Janes (40) who finds the period fluctuating rather than progressively lengthening. Arp (6, 7) has derived light-curves of cepheids in two colors in NGC 1866, based on Radcliffe plates secured in part by Thackeray. The colors, amplitudes and light curves are essentially independent of period (ranging from 2·64 to 3'53 days). Short-period variability in some bright LMC supergiants has been looked for in vain by Bok et al. (13). Spectra of S Dor during a record deep minimum (from which it has not yet recovered) have been described by Thackeray (52).

o·s

s·o

3· Radio and Gaseous Components Detailed results of 21 em surveys with the 210ft (64 m) Parkes telescope have been published for the LMC by McGee and Milton (44, 45, 46, 48) and for the SMC by Hindman and Balnaves (31, 32, 33, 48). McGee detects 52 large HI complexes in the LMC. He attributes the very complicated velocity pattern to two pairs of spiral arms in planes differing by about 20°, The bridge between SMC and LMC has been resolved with the Parkes equipment into patchy condensations. Hindman has given further details of the double-peaked 21cm profiles in the SMC. The pattern is attributed to expanding shells; the absence of a non-thermal component associated with supernova shells is to be noted and may perhaps be due to an ageing effect. He has

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found the first evidence of a rotation curve for the SMC with tum-over points and a rather surprisingly large velocity gradient; the maximum gradient is in p.a. 55°, similar to the major axis of Lindsay's distribution of clusters. Westerlund and Mathewson (61) identify Henize nebulae N49, 63A, I32D in the LMC with non-thermal sources and attribute them to remnants of Type II supernovae. Broten (48) has surveyed the LMC at I I em vd.th the Parkes telescope. Over 50 sources are found, with the strongest coinciding with H II regions. Mills (48) reports preliminary observations of the Clouds with the EW arm of the Cross radio telescope at 408 MHz. The H I content of the Clouds is listed for comparison with that of other galaxies by Epstein (16). Dickel (14) has determined electron densities and masses of 8 LMC and I SMC H II regions from low-resolution scans with results that are matched by many galactic H II complexes (larger and less dense than the Orion nebula). Feast (19) in a complementary investigation based on coude spectra, determines electron densities and masses of 36 LMC and 2 SMC nebulae from measures of the [0 II] 3726/3729 ratio combined with Michigan measures of Hex surface brightness; three nebulae are common to Mrs Dickel's list. The general conclusions are similar. Feast's densities run higher, partly at least because his analyzing slit was very much narrower; his total masses run smaller. Aller and Faulkner (5) compare 30 Dor and Eta Car nebulae by photoelectric spectrophotometry; abundances (HefH, 0/H}, electron temperatures and densities are compared. No differences in abundance ratios greater than 40% can be found. Mathis (47) has also studied the inner regions of 30 Dor with results that resemble galactic nebulae fairly closely. Faulkner (17) in a further study of 30 Dor compares surface brightness in Balmer lines with radio fluxes. He derives R = 7 for the ratio AvfEn-v· Feast (18) has observed spectra of ten planetaries and finds a rotation curve for the Cloud similar to that from Population I stars. The velocity dispersion is 22 ± 7 km s-1• This program is being continued and Feast has now material on 37 plar.etaries (both Clouds). Webster (48) gives preliminary results of velocities of Cloud planetaries. Bok et al. (n) have measured radial velocities of nine emission nebulae in the bar of the SMC for comparison with the 2I em velocities. A third list of 446 emission-line objects in the LMC discovered on ADH objective prism spectra is given by Andrews and Lindsay (2). 4· Clusters

Gascoigne (30) has completed a major program on color-magnitude diagrams of nine Cloud globular clusters down to V,...., I9"5· Among these he recognizes three types: {I} NGC 1466, 2257 (both containing known RR Lyr variables) and I84I have arrays like that of Tifft for NGC I2I, and all are similar to galactic halo clusters; (2) Lindsay I, Kron 3 and NGC 339 (all SMC) have no blue horizontal branch despite blue integrated colours and are regarded as of intermediate age; (3) NGD 2209, 223I and Hodge I I (all LMC) differ in having a very weak (or no) giant branch but many faint blue stars; this type has no known galactic counterpart. Gascoigne (48) has also measured integrated colors of 6o Cloud globulars and confirms the two-fold grouping in color; there is an almost complete absence of colors (B - V) between o·3o and o·6o. Arp (6, 8) has completed his study of the e-m array of NGC I866 which contains many red giants (B - V = + o·6 to + I·S) despite its early-type integrated spectrum. He assigns an age a little less than Io8 years and finds some evidence in favour of evolutionary tracks predicted for stars of mass 5 M®. There appears to be a progressive reddening of giant branches of globular clusters in SMC, LMC and the solar neighborhood. Hodge and Sexton

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(36) have listed 457 new clusters in the LMC. Lindsay (41) has commented on the classification of some objects listed as clusters by Lynga and Westerlund. Lindsay (42) has also identified most of the 366 NGC objects in the LMC region on ADH plates. He lists 26 (almost entirely in the outer regions) as galaxies. Renewed attempts at measuring radial velocities of Cloud globulars are being made at the Radcliffe Observatory. 5· General Field (a) e-m arrays and photometry Woolley and Epps (64) have studied colors of stars down to about 16·5 m (two magnitudes fainter than an earlier proper-motion study) and conclude that in the relevant LMC field the great majority of stars with B - V between + o·5 and + 1·5 are foreground. Basinski et al. (9) have derived a e-m array down to V = 15·0 for a dense region of the SMC. They find numerous stars with B - V < + o·4 (approximately equally divided into groups - '4 too and o to +·4 and some stars with B- V > + 1·2o). They also attribute stars of intermediate color to the foreground. The same team have continued to study NGC 1929-37 (LMC). According to a preliminary report by Bok (48) the core of the region is dominated by blue stars, while further out (after allowance for foreground stars) some yellow-red stars appear which may represent evolved stars expelled from the central core. Hodge (37) has published a corrected p-e sequence and e-m array for 938 stars in the LMC. UBV photometry of LMC supersupergiants is being undertaken by P. J. Andrews. Walraven (55) is also working on multi-color photometry of Fehrenbach stars. He has observations on his system of 365 and 274 stars in the region of SMC and LMC respectively of which at least 45% are Cloud members. Westerlund (48) divides each of the Clouds into four sub-systems according to age, partly on the basis of colors.

(b) ~pectroscopy Hutchings (39) has published measures of Hy equivalent widths for 149 Cloud supergiants (0 to Ks). The variation with spectral type shows a maximum near Fo. Approximate distance moduli (corrected for absorption) of 18·2 (LMC) and 18·3 (SMC) are derived. Przybylski (49) has carried out a curve of growth analysis of the brightest known LMC member, HD 33 579, and finds Lllog N (Fe, Cr, Ti/H) relative to the Sun of - o·2 ± o·2. J. A. Williams (62) has also studied the metal/H ratio of long period Cloud cepheids by means of four-color intermediate band photometry. He finds no significant differences in the metal indices for either Cloud and the solar neighborhood. L. F. Smith (So) has classified 41 Cloud WR stars through narrow band photometry and some spectra. The order of decreasing luminosity appears to be WN7-8-6 (rare)-WCs- WN5. Dessy is obtaining spectra of the brightest Cloud stars at 42Ajmm for inclusion in an Atlas of Spectra in collaboration with the Jascheks. (c) Radial Velocities Fehrenbach (2o) has recapitulated his group's lists of stars with large and small velocity in the direction of the LMC. Fehrenbach et al. (2o) have published radial velocities of III stars in a central region of LMC of which 29 are attributed to the Cloud. Fehrenbach (21) reported at IAU Symposium no. 30 on further progress in this program and on the extension of his survey to regions between the Clouds and between LMC and Galaxy where several high velocity stars have been found. Florsch and Carozzi (22) have found 33 highvelocity stars between the Clouds of which they regard 21 as probable members. Slit spectra of all the later type LMC members, m < 12, revealed by Fehrenbach's survey are being obtained at the Radcliffe Observatory. Thackeray (53) has published two instances

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of high-velocity galactic subdwarfs and it is clear that the objective prism velocities are not a completely sure criterion of Cloud membership. Radcliffe slit spectra of SMC stars are also being secured for improved radial velocities. Wayman (56) has proposed a technique for separating foreground stars among the later types through narrow-band photometry. Gollnow (48) has reviewed the general problem of observed radial velocities in the Clouds. (d) Polarization and Absorption Visvanathan (54, 48) has published his polarization measures of 30 LMC stars. His discussion suggests that the Cloud is seen nearly face-on with a magnetic field related to Cloud structure. The polarization is correlated with color excesses derived from Radcliffe photometry and spectra. Hutchings (38) has published details of his important discovery of 443oA absorption in both Clouds. The correlation of strength and color excess is similar to that found for galactic stars. Wesselink (59) has further discussed selection effects due to absorption in the discovery of variables. He is inclined to attribute the displacement of the LMC centre of rotation from the bar to heavy absorption distorting the optical picture.

7· Summary of Trends and Future Needs The comparison of the Clouds with each other and with the Galaxy, particularly as regards cepheids and the P-L relation, continues to be of fundamental interest. Extensive statistics of cepheid periods and light-curves may have encouraged early belief in differences in composition, which would serve as a key to evolutionary theory. The differences sought, however, have become elusive. For example, the 'unusual' galactic cepheid TV Cam resembles the SMC cepheids in its light-curve, and was at one time thought to display abundance anomalies in its spectrum. These are now attributed to low turbulent velocity by Abt et al. (1). Further study of the P-L relation could be planned to examine questions of tilt of the two systems, especially in view of Hindman's model of the SMC viewed nearly edge-on. It would be logical if further plans, especially in the choice of fields were coordinated with this problem in mind together with provisions for an adequate degree of overlap. Uncertainty in the masses of the Clouds, arising largely from uncertainty in their tilts (see Bok (10)) should be resolved in order to clarify the problem of tidal interactions between the Clouds and Galaxy. Kerr (48) discusses such interactions as possibly associated with the warped H I galactic plane, north-south asymmetry in the H I rotation curve, and the highvelocity thin HI clouds observed at Leiden {ln = 120, bu = + 40). The complexities of radio patterns revealed by the Parkes telescope have posed many problems whose solution depends in part on the slower approach of optical astronomers. Visvanathan's work on optical polarization deserves to be prosecuted. Narrow-band photometry could be pushed to fainter limits. Hj3 photometry could be used for improved distance moduli; Hutchings' Hy equivalent widths refer only to the brightest supergiants and may frequently be affected by shell absorption or superposed emission. The luminosity function in different parts of the Clouds is an important datum in evolutionary theory. It has been discussed by McCuskey (43) in the light of former star-counts. There are many suggestions of bursts of local star formation in regions up to 1 kpc across. Even at magnitude 15-16 the contribution of galactic foreground can be very serious and statistical corrections may be misleading. Multicolor photometry at this level would probably offer the safest criterion of membership. For the brightest stars, Fehrenbach's survey supplemented by slit spectra is leading to a fairly complete census. G2

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It is now generally accepted that both Clouds contain Populations I and II. But our knowledge of Population II components is severely limited. Gascoigne's e-m arrays of globular clusters underlines the recognized need for radial velocities - an especially difficult problem for the red globulars. Continuation of Dessy's search for long period variables is required and is being attempted at the Radcliffe Observatory. Perhaps the most neglected field in recent Cloud research has been the search for novae. Several must have been missed since the abandonment of the Harvard patrols in the last decade. A small resumption has been begun by Sterling (51) in association with the Radcliffe Observatory. With many telescopes capable of following up a discovery, the importance of immediate blinking of search-plates, with accurate information on position and nearest bright star cannot be overstressed. BIBLIOGRAPHY

1. 2. 3· 4· 5· 6. 7· 8. 9· 10. 11.

12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33· 34• 35·

Abt, H., Osmer, P. S., Kraft, R. P. 1966, Astrophys. J., 145, 479· Andrews, A. D., Lindsay, E. M. 1964, Irish astr. J., 6, 241. Andrews, A. D. 1965, Irish astr. J., 7, 79· Andrews, A. D. 1966, Inj. Bull. S. Hemisphere, no. 8, 23. Aller, L. H., Faulkner, D.]. 1965, Mon. Not. R. astr. Soc., 130, 393· Arp, H. C. 1965, IAU 3rd Colloquium on Variable Stars. Kl. Vero.ff. Remeis Sternw. Bamberg, 4, no. 40, 209. Arp, H. C., Thackeray, A. D. Astrophys. J. Submitted 1966. Arp, H. C. Astrophys. J. Submitted 1966. Basinski, J. M., Bok, B.]., Bok, P. F. 1966, Mon. Not. R. astr. Soc., in press. (Summary also in Publ. astr. Soc. Pacij., 78, 439, 1966). Bok, B.]. 1966, Ann. Rev. Astr. Astrophys., 4, 95· Bok, B. ]., Gollnow, H., Hindman, J. V., Mowat, M. 1964, Austr. J. Phys., 17, 404. Bok, B. ]. 1965, Publ. astr. Soc. Pacij., 77, 416. Bok, B.]., Kidd, C., Routcliffe, P. 1966, Pub!. astr. Soc. Pacij., 78, 333· Dickel, H. R. 1965, Astrophys. J., 141, 1306. Dickens, R. ]. 1966, Observatory, 86, 18. Epstein, E. E. 1964, Astr. J., 69, 503. Faulkner, D. J. 1966, Mon. Not. R. astr. Soc., In press. Feast, M. W. 1964, Observatory, 84, 266. Feast, M. W. 1964, Mon. Not. R. astr. Soc., 128, 327. Fehrenbach, Ch., Dufiot, M., Dufiot, A. 1965, J. Observateurs, 48, 185, 199. Fehrenbach, Ch. 1966, IAU Symposium no. 30 (Toronto). In press. Florsch, A., Carozzi, N. 1965, Comm. ESO, no. 5· Gaposchkin, C. P. 1965, IAU 3rd Colloquium on Variable Stars, Kl. Vero.ff. Remeis Sternw. Bamberg., 4, no. 40, 178. Gaposchkin, C. P., Gaposchkin, S. 1966, Vistas in Astronomy, 8, 191. Gaposchkin, S. 1965, Pub!. astr. Soc. Pacij., 77, 127. Gaposchkin, S. 1966, Smithson. Contr. Astrophys., 9, I. Gaposchkin, S. 1965, IAU 3rd Colloquium on Variable Stars, Kl. Vero.ff. Remeis Sternw. Bamberg., 4, no. 40, 66. Gaposchkin, S. 1965, IAU 3rd Colloquium on Variable Stars, Kl. Vero.ff. Remeis Sternw. Bamberg., 4, no. 40, 76. Gascoigne, S. C. B., Kron, G. E. 1964, Mon. Not. R. astr. Soc., 130, 333· Gascoigne, S. C. B. 1966, Mon. Not. R. astr. Soc. In press. Hindman, J. V. 1964, Nature, 202, 377· Hindman, J. V., Balnaves, K. M. 1966, Austr. J. Phys. Suppl. In press. Hindman, J. V. 1966, Austr. J. Phys. In press. Hodge, P. W., Wright, F. W. Smithsonian Astrophysical Observatory, 1966. See also Astr. J., 64, 565, 1964. Hodge, P. W., Wright, F. W. 1966, Astr. J., 71, 131.

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1966, Astr. J., 71, 363. 36. Hodge, P. W., Sexton, S. 196s, Astrophys. J., 141, 8o6. 37· Hodge, P. W. as. Hutchings, J, B. Ig66, Mon. Not. R. astr. Soc., IJI, 299· 1966, Mon. Not. R. astr. Soc., 132, 433· 39· Hutchings, J. B. 1964, Astr. J., 69, 131. 40. Janes, K. A. 1964, Irish astr. J., 6, 233· 41, Lindsay, E. M. 1964, Irish astr. J., 6, 286. 42· Lindsay, E. M. 1966, Vistas in Astronomy, 7, 141. 43· McCuskey, S. W. 1964, Austr. J. Phys., 17, sxs. 44· McGee, R. X. 1966, Austr. J. Phys., 19, 343· 45· McGee, R. X., Milton, J, A. 1966, Austr. J. Phys. Suppl., no. 2. 46. McGee, R. X., Milton, J, A. 1965, Publ. astr. Soc. Pacif., 77, 189. 47· Mathis, J. S. 48. Mt Stromlo Symposium on the Magellanic Clouds. (Edited Hindman, J, V. & Westerlund, B. E.), 1965. 1965, Nature, 205, 163. 49· Przybylski, A. 1966, Private Communication. 50. Smith, L. F. 1966, lnf. Bull. S. Hemisphere, no. 8, 27. 51. Sterling, K. L., Wolterbeek, J. 1964, Mon. Not. R. astr. Soc., 129, 169. 52. Thackeray, A. D. 1966, Observatory, 86, 6o. 53· Thackeray, A. D. 1966, Mon. Not. R. astr. Soc., 132, 423. 54· Visnanathan, N. 1966, Private Communication. 55· Walraven, Th. 1966, IAU Symposium no. 30 (Toronto), p. 89. 56. Wayman, P. A. 1965, Mon. Not. R. astr. Soc., 130, 443· 57· Wesselink, A. J,, Shuttleworth, M. 1965, IAU 3rd Colloquium on Variable Stars. Kl. Verojj. Remeis. Sternw. 58. Wesselink, A. J. Bamberg, 4, no. 40, x8x. 1966, Astr. J., 71, x8s. 59· Wesselink, A. J. 1964, Observatory, 84. 253· 6o. Westerlund, B. E. Mon. Not. R. astr. Soc., 131, 371, 1966; Astr. J .• 61. Westerlund, B. E., Mathewson, D. S. 69, s63, 1964. 1966, Astr. J., 71, no. 3· 62. Williams, J, A. 1964, R. Obs. Bull., no. 82, Eg6. 63. Woolley, R.v.d.R. 1965, R. Obs. Bull., no. go, E313. 64. Woolley, R.v.d.R., Epps, E.

APPENDIX VI. INVESTIGATIONS IN EXTRAGALACTIC ASTRONOMY MADE IN THE U.S.S.R. DURING 1964-66

(Prepared by B. Vorontsov-Velyaminov)

Photometry, Colorimetry, Polarization Markarian, Oganesian and Arakelian made a detailed photometry and colorimetry of E and SO galaxies (1) and of spiral galaxies (2) in the Virgo cluster. The principal regularities observed in the distribution of brightness and color' in the images of galaxies were noted. E and SO galaxies were studied: NGC 4374, 4406, 4435, 4458, 4459, 4461, 4473, 4477, 4478, 4486, and spirals: NCG 4371, 4388, 4402, 4438, 4440, 4501. The main features of their structure were noted. Kalloghlyan (3) measured photographically the surface brightnesses of bars of nine brighter SB galaxies. He found the mean value to be 201!1-9 per square second of arc and concluded that this brightness is constant, which was confirmed by the comparison of the angular dimensions of the bars with the integrated brightness of many SB galaxies. SB galaxies and Later Kalloghlyan and Tovmassian (4) made a two-color photometry of classified their nuclei from the point of view of their structure. Besides, Tovmassian (5) from the observations of 20 SB galaxies discussed the distribution of nuclei depending on their structure. Kalloghlyan (6) performed also the two-color photometry of the interacting galaxy NGC 3656 and described the structural peculiarities of this double system.

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Artamonov, Vorontsov-Velyaminov and Dibai (7) published the isophotes of the spiral galaxy NGC 2861. Vorontsov-Velyaminov (8), using the photographic measurements of stellar magnitudes of 200 galactic nuclei made by Gorbatschev (9) and the published photoelectric measurements of galaxies, compiled a catalog, which gives for 173 nuclei their apparent and absolute magnitudes, surface brightnesses, and luminosities per unit volume. They all are similar to the corresponding characteristics of Zwicky's compact galaxies. The luminosity of the nuclei increases with the luminosity of galaxies. Gorbatschev (Io) studied the distribution of absolute luminosity in the nuclei of NGC 1300, 4051, 4040 and 4548 and, using Spinrad's model of the M31 nucleus, calculated the ,density distribution and the masses of these galaxies. Vorontsov-Velyaminov's group obtained the isophotes for several peculiar and interacting galaxies (in press). Gagen-Torn (n) from the photographic and photoelectric observations studied the polarization distribution in NGC 3077, which points to the presence of dust in this galaxy. Dombrovsky (12) detected photoelectrically polarization in the nuclei of M51 and NGC 1068. Dibai and Schahovskoy (I3) measured polarization in the nuclei of the Seyfert galaxies, but found it only in the radiogalaxies NGC 1068 and 1275.

Morphology of Galaxies Vorontsov-Velyaminov described some new morphological types of galaxies, which show their large variety and the repetition of some 'peculiar' forms. Vorontsov-Velyaminov and Davydov (IS) from the photographs with interference filters found a difference in the distribution of hydrogen and of [0 m] in M82. Gurzadian (I6) explained the presence of the hydrogen absorption lines in the spectrum of M82 not by the presence of numerous hot stars, but by the light absorption, by interstellar hydrogen inside this galaxy and by the presence of relativistic electrons. Markarian (I7) studied ten irregular galaxies, which he considered to belong to the M82 type. He concluded that the discrepancy between the colour and the spectrum cannot be accounted for by the influence of dust and suggested that the early type of their spectra were due to some unusual emission. Ambartsumian {IS) analyzing the data on the galaxies of M82 type concluded that they are young and that their luminosity increases in the course of time. The relationship between the physical state of the nucleus and the evolutionary phase of the galaxy was discussed. Markarian (I9) also investigated other galaxies with anomalous spectral characteristics as regard their type and drew up a list of them. The conclusion was drawn that the peculiarly blue color of their nuclei is due to the additional ultraviolet emission of unusual nature. Vorontsov-Velyaminov (20) described eight types of peculiar nuclear regions and established that hot nuclei with traces of spiral structure occur among a third of the galaxies of SAB and SB families. Some of their physical characteristics were determined. Vorontsov-Velyaminov (2I) showed that the structure of the flat component of many galaxies is in favor of the presence of magnetic-like phenomena: loops, eight-forms, intersections of the arms, etc. However, some data do not confirm the magnetic forces hypothesis. Zasov (zz) found 13 galaxies where the layer of dark matter is inclined to the equatorial plane and suspected this inclination in 17 galaxies. To explain this he turns to the hydrodynamical interaction of the layer with a current of intergalactic gas outflowing the galaxy. Ambartsumian, Iskudarian, Shachbazian and Sahakian (23) described the powerful associations of 30 Doradus type in the LMC. They call them superassociations. The latter are most frequent in the supergiant Sc and in irregular galaxies. A list of galaxies with superassociations is given. Markarian (24) quoted examples of isolated chains of six and more galaxies. The calculation of the probability of an accidental formation leads to the conclusion that the majority of the chains must be real physical systems. Karachenzev (25) studied the distribution

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of galaxies and the structure of the supercluster in Hercules. He (26) has also found 165 dwarf galaxies in the Virgo cluster and established their statistical relation to the bright galaxies Sand E. Richter and Sahakjan (27) discovered 54 remote blue objects and studied their distribution. Vorontsov-Velyaminov (27a) showed that the number of globular clusters relate neither to luminosity nor to mass of the galaxy, though generally there are less globular clusters in small galaxies. Statistics and Kinematics of Galaxies and of QSS

The Morphological Catalog of galaxies (MCG) provides an exhaustive source for statistical investigations and for the compilation of observational programs. Now with the publication of the II and IV volumes this catalog, compiled by Vorontsov-Velyaminov and Arhipova (28, 29), is complete. It gives the coordinates, integrated and surface brightness, dimensions, inclination, description and all other known data for 34 ooo galaxies 15m and brighter to the north of o = - 33°. Among them 1765 interacting, 4700 double and multiple systems are noted. Zvyagina (30) from the counts of faint galaxies in small areas around galaxies of 13m to 14m finds that statistically more than a half of them have dwarf companions. The number of galaxies with increasing number of companions drops quickly. Denisjuk (31) discussed the possibility of finding the orientation of an elliptical galaxy in space with respect to the observer. Roslyakova and Gainullina (32) gave a theoretical interpretation to the fact that the symmetry planes of bright E galaxies tend to pass through the center of compact clusters. Agekjan and Sumsina (33) found a connection between momenta of apparent and real sphericity of galaxies in 90 clusters. The squares of the sphericity are different, sometimes negative. This points to the preponderance of orientation or to the existence of needle-like galaxies. Veltman (34) in his papers, based on the Schuster law, constructed the phase and hydrodynamical models with radially elongated velocity distribution. In the last case the dispersions of velocity are expressed through hypergeometric functions. Karachenzev concludes that the clusters Virgo (35) and Coma (36) are not stable. From counts of 54 ooo galaxies in the region of the North Galactic Pole he (37) finds, using the angular diameters, that the average density of Metagalaxy is 1·2 x 10- 31 g cm- 3 and makes the inference that the new galaxies are formed in the lapse of time. Pskovsky (38) estimated the density and mass of the Coma clusters (4 x 1014M®) and, accepting that the clusters occupy 1% of the whole volume, evaluated the density of the Metagalaxy as 7 x 10- 30 g cm- 3 • Karachenzev (39) determined the ratio of the virial mass to luminosity for multiple galaxies and clusters and concluded that the non-stability of systems increases with their luminosity. He believed this to be akin to the expansion of the Metagalaxy. Zasov (40) studied the correlation of the distance moduli with the red shift of galaxies taking into account the influence of the latter on the apparent luminosity. He has found that the second order term in the relation describing the deceleration of expansion equals - 2·2 (from the luminosity of the 1oth galaxy in clusters). Pskovsky (41) established the connection of opticallimunosity with radio index and obtained the luminosity function of normal galaxies in the photographic and in the radio region. He (42) studied the correlation of radio luminosity with the spectral index and linear dimension and obtained the radio-luminosity distribution which proved to be monotonic. Zasov and Ozemoi (43) determined the luminosity function of QSS for different models of the Universe in radio and optical frequencies. The continuous transition of the function from radio galaxies to the quasi-stellar radiosources points to their genetic connection. Spectra and Spectrophotometry of Galaxies and QSS

Dibai and Pronik investigated spectrophotometrically the Seyfert galaxies NGC 1068 (44), 1275 (45) and others (46); Dibai and Vorontsov-Velyaminov (47)-NGC 4151; and Dibai,

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Esipov and Pronik (48)-NGC 5548. They calculated the physical conditions in the two systems of gas in all these nuclei and the probable excitation mechanism. Dibai and Pronik (49) made also the spectrophotometry of QSS 3C 273 and determined the physical parameters in its gaseous envelope. Dibai and Esipov (50) measured the red shift in the spectrum of 3C 345 and noticed the changes of the profile of Mg II line. They detected Hoc emission in the nucleus of NGC 4486, estimating its gas content and obtained (52) the spectra of ten faint blue objects in high galactic latitudes. Object Tonanzintla no. 256 has a spectrum similar to that of the nuclei of the Seyfert galaxies. Pronik (53) obtained the spectrophotometric characteristics of QSS CTA-102 and estimated the mass of gas to be above 1o6M®.

Supernovae Dibai, Esipov and Pronik (54) studied the energy distribution in the spectra of Chavira and Rosino. 1965 supernovae. Kukarkin (55) and Ambartsumian (56) noticed the very high frequency of supernova I outbursts in giant spirals of late types and Pskovsky (57) gave the characteristics of an object near radiosource 3C 386 considering it as being a supernova of anno 1230.

Cosmogonic Hypotheses According to Pickelner's hypothesis (58) the spiral arms appear when the primordial gas in the center is contracting with a subsequent propagation of a condensation wave along the magnetic tube. Their thickness depends on the star density in the disk. This explains the difference in the arm structure in the galaxies of the Sa, Sb and Sc types. The propagation of the condensation wave in the gas cloud which surrounds the galaxy can explain the formation of the tails and of the connecting filaments in the interacting galaxies. Another possibility of their formation was pointed out by Gerschberg (59). It is the twisting of the magnetic field with the relative rotation of galaxies which lie on one and the same tube of force lines. Sb galaxies require the absence of differential rotation and according to Pickelner (6o), the explosion in a gaseous proto-galaxy pushes the gas off center creating the homogeneous sphere of old stars. The flow of gases to the ends of the bar, rings and other structures is also explained. Notice. In this review there are not included: cosmology, radioastronomical studies of galaxies, theoretical speculations concerning QSS, as well as discoveries and photometric observations of supernovae. REFERENCES I, 2.

3· 4· 5· 6. 7· 8. 9· IO. II.

12.

I3.

I4. IS.

Markarian, B. E., Oganesian, E. J., Arakelian, S. N. 1965, Astrofizika, I, 38. Markarian, B. E., Oganesian, E.]., Arakelian, S. N. 1965, Astrofizika, 2, 55· Kalloghlyan, A. T. 1963, SoobSc. Bjurakan. Obs., 33, 19. Kalloghlyan, A. T., Tovmassian, H. M. 1964, SoobSc. Bjurakan. Obs., 36, 31. Tovmassian H. M. 1965, Astrofizika, I, 197. Kalloghlyan, A. T. 1963, SoobSc. Bjurakan. Obs., 34, 31. Artamonov, V. P., Vorontsov-Velyaminov, B. A., Dibai, E. A. 1966, Astr. Zu., 43, 557· Vorontsov-Velyaminov, B. A. 1965, Astr. Zu., 42, 1168. Gorbatschev, B. I. 1966, SoobSc. gos. astr. Inst. Sternberga, no. 148. Gorbatschev, B. I. 1966, Astr. Zu., 42, 46. Gagen-Torn, V. A. 1966, Trudy astr. Obs. Leningr. Univ., 24. Dombrovsky, V. A. Vestnik Leningr. Univ. (in press). Dibai, E. A., Schahovskoy, N. M. Astr. Circ. Akad. N. SSSR (in press). Vorontsov-Velyaminov, B. A. 0. Struve's memorial volume. Italy (in press). Vorontsov-Velyaminov, B. A., Davydov, V. D. 1965, Astr. Circ. Akad. N. SSSR, no. 316.

GALAXIES

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1963, Soob!c. Bjurakan. Obs., 34, 36. Gurzadian, G. A. 1963, Soob!l. Bjurakan. Obs., 34, 18. Markarian, B. E. 1964, 13eme Conseil de Physique. Solvay, Bruxelles. Ambartsumian, V. A. 1963, Soobsl. Bjurakan. Obs., 34, 3· Markarian, B. E. IAU Symposium no. 29 (in press). Vorontsov-Velyaminov, B. A. 1964, Astr. Zu., 49, 814. Vorontsov-Velyaminov, B. A. 1965, Astr. Circ. Akad. N. SSSR, no. 334· Zasov, A. V. I963, Ambartsumian, V. A., Iskudarian, S. G., Shachbazian, R. K., Sahakian, K. A. Soobll. Bjurakan. Obs., 33, 3· I963, Sooblc. Bjurakan. Obs., 33, 29. 24. Markarian, B. E. 1964, Izv. Akad. Nauk Arm. SSR, ser. fiz.-matem., I7, I09. 25. Karachenzev, I. D. 1965, Astrofizika, I, 203. 26. Karachenzev, I. D. 1965, Mitt. Sternw. Tautenberg. no. 24. 27. Richter, R., Sahakjan, K. 1966, Astr. Zu., 43, 231. 27a. Vorontsov-Velyaminov, B. A. 1964, Morphological Catalogue of Galaxies. 28. Vorontsov-Velyaminov, B. A., Arhipova, V. P. Vol. II, Moscow. Morphological Catalogue of Galaxies. 29. Vorontsov-Velyaminov, B. A., Arhipova, V. P. Vol. IV, Moscow (in press). 1966, Astr. Zu., 43, 34· 30. Zvyagina, E. V. 1966, Trudy astrofiz. Inst. Akad. N. KazSSR, 7, 45· 3I. Denisjuk, E. K. 1965, Trudy astrofiz. Inst. Akad. N. KazSSR, 5, 32. Gainullina, R. H., Roslyakova, T.V. 237· (in press). 33· Agekjan, T. A., Sumsina, N. K. 1964, Publ. Obs. Tartu, 34, 81, 101, 114; 1965, Soobic. Obs. Tartu, no. 18, 34· Veltman, U. I. 1965, Astrofizika, I, 303. 35· Karachenzev, I. D. 1964, Izv. Akad. Nauk Arm. SSR, Ser. fiz.-matem, I7, 104. 36. Karachenzev, I. D. 1964, Dokl. Akad. N. SSSR, I58, 815. 37· Karachenzev, I. D. 1965, Astr. Zu., 42, 323. 38. Pskovsky, Y. P. 1966, Astrofizika, 2, I. 39· Karachenzev, I. D. 1963, Astr. Zu., 40, 868. 40. Zasov, A. V. 1965, Vestnik Mask. gas. Univ., no. I, 3· 4I. Pskovsky, Y. P. 1964, Astr. Zu., 4I, 619. 42· Pskovsky, Y. P. · 1965, Astr. Circ. Akad. N. SSSR, no. 334· 43· Zasov, A. V., Ozemoi, L. M. 1965, Astrofizika, I, no. I. 44· Dibai, E. A., Pronik, V. I. Izv. Krym. astr. Obs., 35, (in press). 45· Dibai, E. A., Pronik, V. I. Astr. Zu. (in press). 46. Dibai, E. A., Pronik, V. I. IAU Symposium no. 29 (in press). 47· Dibai, E. A., Vorontsov-Velyaminov, B. A. Astr. Zu. (in press). 48. Dibai, E. A., Esipov, V. F., Pronik, V. I. 1964, Astr. Circ. Akad. N. SSSR, no. 282, 286. 49· Dibai, E. A., Pronik, V. I. 1965, Astr. Circ Akad. N. SSSR, no. 349· so. Dibai, E. A., Esipov, V. F. Astr. Zu. (in press). 5I. Dibai, E. A., Esipov, V. F. Astr. Zu. (in press). 52. Dibai, E. A., Esipov, V. F. Astr. Zu. (in press). 53· Pronik, V. I. Astr. Zu. (in press). 54· Dibai, E. A., Esipov, V. F., Pronik, V. I. 1965, Astrofizika, I, 465. 55· Kukarkin, B. V. 1965, Astrofizika, I, 473· s6. Ambartsumian, v. A. 1965, Astr. Zu., 42, 683. 57· Pskovsky, Y. P. 1965, Astr. Zu., 42, 515. 58. Pickelner, S. B. 1965, Astr. Zu., 42, 330. 59· Gerschberg, R. E. 1965, Astr. Zu., 42, 3· 6o. Pickelner, S. B. I6. I7. I8. I9. 20. 2I. 22. 23.

29. COMMISSION DES SPECTRES STELLAIRES PRESIDENT: Dr J. Sahade, Observatorio Astron6mico, La Plata, Argentina. VICE-PRESIDENT: Dr M. W. Feast, Radcliffe Observatory, P.O. Box 373, Pretoria, South Africa. CoMITE n'ORGANISATION: Y. Andrillat, A. Boyarchuk, Y. Fujita, J. B. Oke, K. 0. Wright. MEMBRES: Abt, Aller (L. H.), Andrillat (H.), Asaad, Babcock (H. W.), Bappu, Bartaya, Beals, Berger, Bertaud, Bidelman, Bloch, Boggess, Bouigue, Bretz, Briick (H. A.), Burbidge (E. M.), Buscombe, Cayrel (R.), Chalonge, Code, Deutsch (A. J.), Divan, Dobronravin, Dolidze, Dufay (J.), Dunham, Elvius (T.), Evans (D. S.), Fringant, Gollnow, Gorbatsky, Gratton, Greenstein, Griffin (R. F.), Groth, Guthrie, Gyldenkerne, Hack, Haro, Heard, Herbig, Herman, Huang, Hunaerts, Iwanowska, Jaschek (C. 0. R.), Jugaku, Keenan, Kienle, King (R. B.), Kopylov, Kraft, Kuprevich, Lamia, Larsson-Leander, McCuskey, McLaughlint, McNamara, Mannino, Mayall (M. W.), Melnikov, Miczaika, Milligan, Morgan, Munch (L.), Mustel, Nassaut, Nicholls, Nikitin, Oetken, Osawa, PayneGaposchkin, Pedoussaut, Platzeck, Przybylski, Richter, Roman, Rosen, Rozis-Saulgeott, Schalen, Searle, Slettebak, Smak, Stawikowski, Stecher, Stephenson, Stromgren, Swensson, Swings, Taffara, Thackeray, Thompson (G. 1.), Underhill, Vandekerkhove, Van t'Veer-Menneret, Voigt, Wehlau, Wellman, Wempe, Westerlund, Willstrop, Wilson (0. C.), Wilson (R.), Wyller. The writing of the Draft Report of Commission 29 brings to light once again the need of better defining the province of its domain since there is an overlap with areas of other commissions such as 27, 30 and 42, which use stellar spectra for the investigations they are concerned with. In what follows I have tried as far as possible not to include whatever would naturally go into the Draft Reports of other commissions and whatever Dr Feast has already included in his report on the spectra of variable stars for Commission 27. As a result, the report on some items is only fragmentary. In my task, I have had the help of the Vice-President and of the members of the Organizing Committee who have prepared reports of the work done in the southern hemisphere, Europe (except U.S.S.R.), U.S.S.R., Japan and Canada, respectively. Dr Oke contributed a report on abundances which I have incorporated within the information under this heading. Mme Herman prepared a report of her working group on Be stars from which I have extracted whatever was relevant to our Commission. I am very grateful to all of them for their help. I am also grateful to Drs Oke and Cayrel de Strobel for the reports concerning the Committees they head. They are appended at the end of this report. The report and the bibliographical references reflect the enormous amount of work in the field of stellar spectra done in the last three years. Commission 29 is very large indeed but it is also most active. Although there must certainly be better ways of doing it, the report has been divided in two main sections, namely, general spectroscopic studies and abundance determinations. Of course, in trying to fit the report information into the two sections some material that should have perhaps been included in the second one was considered better fitted for the first section. Last but not least, I would like to express my gratitude to the Vice-President and to the members of the Organizing Committee for their contribution to the bibliography. 607

608

COMMISSION 29 I. GENERAL SPECTROSCOPIC STUDIES

(a) Early-Type Stars

Miss Underhill (1966a) has taken the task of putting together and discussing the observational results of early-type stars and has suggested (Underhill 1965) that the persistence of the Mg II 4481 doublet in 0-type stars is due to the fact that the very high ionization potential for Mg III forces most Mg atoms to stay in the first stage of ionization, even at the high temperatures of the 0 stars. Underhill and de Groot (1964) have published identification and equivalent widths of the spectral lines of 10 Lacertae in the range ..\A 3074-5160 A; it was possible to identify only about 8o% of a total of 2000 lines, and Ne and 0 were found. An interesting fact found by van Heiden (1966) is that in 10 Lacertae the profiles and intensities of 0 II and Fe III vary in time intervals smaller than ten minutes, while the radial velocities display irregular short period variations, according to Grygar's (1964) measures. Y. Andrillat and L. Houziaux (r966a) have studied 8o B and Be stars in the near infrared, compare, in 20 of them, the homologous lines of the Balmer and Paschen series and determine the intensity variation of the 0 I triplet at 7772 A in relation with spectral type and luminosity class (1966b). No differences in the atmospheric parameters for the high latitude 0-type stars HD 93 521 and HD 6o 848 and for 0 stars in the galactic plane has been found by Kumaigorodskaya (1967)· P. Smeyers (1966) is interested in determining the profiles of the Mg II ,\,\ 7877 and 7896 A in a B9 V star in order to compare them with the profiles computed from a model atmosphere. In regard to the B stars, the late R. M. Petrie (1965a) had almost completed his studies of B stars of magnitudes 7 to 9 visible at Victoria and a paper by Petrie and Lee (1966) gives H y measures and luminosities for 571 B stars. A revised luminosity-H y calibration that agrees well with other luminosity studies was also published by Petrie (1965b). From material on OB stars secured at Pretoria and in Cambridge, Andrews (1965) has found that for class V stars, H ex is about as good an absolute magnitude index as H f1 or H y while for supergiants it is more accurate. Aller and Jugaku (1967) have completed a description of their work on the B stars which has resulted in line intensities and line profiles for ,\ Orionis, 10 Lacertae, cp Orionis, g1 Canis Majoris, 15 Canis Majoris, HD 36 959, HD 36 960, 22 Orionis and 114 Tauri. Inspecting the early-type spectra at Victoria, Bidelman has discovered several B-type stars showing variable helium lines. This interesting phenomenon had previously been reported for HR 5378 (Bidelman, 1965) and for the first time in 1957 by Struve, Sahade, Lynds and Huang in Maia (2oc Tauri). At Mt Wilson, Heintze is studying H-line profiles in the sharp line B stars, 'T Herculis, ' Herculis, ' Arietis and ' Draconis to compare them with theoretical line profiles. (b) 'Blue Stragglers'

Deutsch is studying the so-called 'blue stragglers' in M 67 and NGC 752; the spectra obtained confirm and extend Wallerstein and Herbig's results that in most of these stars the spectrum lines are appreciable broadened by stellar rotation. Since the 'blue stragglers' appear to be metamorphs of the late F dwarfs, Deutsch proposes that on the main sequence the solar-type stars suffer a rotational deceleration largely confined to the hydrogen convective zone leaving the radiative core with its angular momentum only slightly diminished even after times of the order of 1010 years.

SPECTRES STELLAIRES

609

(c) Of and Wolf-Rayet Stars

Kumaigorodskaya {I964) has investigated the dependences of emission-line intensities with temperature and luminosity for I3 Of stars and has found that these stars can be grouped in two sequences similar as those of the Wolf-Rayet stars. Nitrogen Of stars appear to be hotter than the carbon Of stars. G. A. Gurzadian and H. S. Tchaurushian {I964) have determined emission line intensities, velocities of expansion of the envelopes and spectrophotometric gradients of the Wolf-Rayet stars HD I65 688, 211 564, 2I3 049 and R 114, while the energy distribution of the continuous spectrum of V 444 Cygni has been studied by lvanova et al. {I965) at different phases; a decrease of the spectrophotometric temperature at the two minima was found. Vainu Bappu and Ganesh are concentrating their efforts in the investigation of the WolfRayet stars and are preparing an atlas of tracings of Wolf-Rayet spectra, which will include a wide range of dispersions, from IO Ajmm to 250 Ajmm. Infrared spectra of HD I92 I03 (WC7), HD I62 763 (WC6), HD 68 273 (WC7), HD I 92 I63 (WN6), HD so 896 (WNs), HD 93 I3I (WN7), HD 92 740 (WN7) and HD ISI 932 (WN 7·5) have been taken and line identifications have been completed; this work will be published in the Kodaikanal Obs. Bull. The two Indian astronomers have also determined excitation temperatures of four WC stars and found values which range from 24 ooo 0 to 57 000°. On the other hand D. M. Pyper {I966) from their UBV colour indices corrected for emission, finds a difference of about 20 ooo 0 between the WN and the WC stars, the WN stars being hotter. At Mt Wilson, Kuhi has studied energy distribution of Wolf-Rayet stars in the range ,\ 3200 to ,\ I I ooo with the Cassegrain photo-electric scanner used as a narrow-band photometer and concluded that they are definitely peculiar and different from those of blackbodies; therefore, no unique temperature can be defined. The apparent different sequences upon which the WC and WNs appear to fall can be explained by emission-line contamination. Kuhi's observations confirmed the behaviour in Wolf-Rayet binaries of He II emission phasewise found previously by Hiltner and also confirmed Sahade's earlier conclusion that ionization decreases outwards in the WR atmospheres; the most highly ionized atoms appear to occur in a geometrically small region and the emitting volume for the lines of lower ionization appear to be very large. Also there seems to be some kind of a reflection effect due to the 0 star. Moreover, Kuhi (I966) has studied the infrared spectrum, from 8ooo to IO 900 A, of some bright Wolf-Rayet stars. R. Barbon et al. {I965) suggest a strong activity in the envelope of the WR stars while Bertola finds that in HD 50 896 the velocities and the profiles of He I 4100 and N IV 4058 are variables although the radial velocity variations do not suggest binary motion. Code and Bless (1964) described the infrared spectra, (from 86oo to IO 830 A) of y 2 Velorum and developed a model for the WR envelope in which collisional processes by particles ejected into a thermalized envelope play an important role in the ionization equilibrium of the envelope. A. Underhill (I966b) has examined the position of the WR stars in the HR diagram and concluded that it is reasonable to consider them as contracting objects that are still approaching the main sequence, in agreement with a suggestion made for the first time in 1958 by Sahade. In this connection it is interesting to note a discussion by Sahade {I965) who pointed out that the presently accepted value for the density of the WR component of V444 Cygni is not reliable. Stepien (1964) has discussed the spectroscopic and photometric data in regard to the WR component of V444 Cygni. New WR stars have been reported by The ( I96fa, b).

610

COMMISSION 29 (d) Intermediate and Late-Type Stars

It is interesting to note that Peat (I964) has been able to establish a way of distinguishing giants from supergiants among the F, G and K stars by plotting the intensity of the Ca II triplet in the red-orange against the intensity of the b-line of Mg 11. The same procedure permits the detection of subdwarfs in the case of high-velocity G and K stars. At the I965 NASA Symposium, Wright (I965) discussed the low excitation temperatures obtained for A- and F-type stars using the Fe I /-values, and at the Trieste Colloquium presented a review paper on the spectra of late-type stars (Wright, I966). Clarke and Grainger (I965) have detected differential polarization effects on the profiles of the H {3 line of y Ursae Majoris, and at Kodaikanal, Bhatnagar has started a programme of observation of the infrared 0 I lines in A and F stars at 250 Ajmm. In regard to the late-type stars, concentrated efforts are being made in Tokyo and in Pasadena. Some of the results obtained in Tokyo by Fujita and his collaborators during the past few years have been recently published (Fujita I966) and special emphasis is being given now to an identification programme that will proceed towards wavelengths shorter than those covered previously in similar work. Yamashita has studied the late-type spectra available at Victoria and found several new CH stars. In South Mrica, Feast is studying coude spectra of southern S-type stars. (e) T Tauri Stars

Herbig has accumulated a considerable amount of information on the infrared Ca II triplet which are characteristically very strong in T Tauri stars, even though they are very weak in dMe stars that have comparable H and K emission intensities; the effect is probably due to heavy self-absorption in T Tauri stars. Herbig (I966) has interpreted FU Orionis as a star which has very recently appeared at the top of the vertical branch of its evolutionary track, an interpretation which implies that the high Li abundances observed in T Tauri stars must have its origin either in the original interstellar material or been produced before the star became luminous in the usual sense. Kuhi has obtained photoelectric spectrum scans of several T Tauri stars from .\ 3200 to >. I I ooo and found that many of these stars are excessively red suggesting that the reddening may be of circumstellar origin. The origin of the peculiar excess ultraviolet emission in T Tauri stars is being investigated.

(f) Giant and Supergiant Stars Zeinalov and Kopylov (I966) have identified about 6oo spectral lines in the spectrum of the Ao Ib star TJ Leonis and carried out a detailed study of the velocity field in its atmosphere. The microturbulent velocity decreases with optical depth while the macroturbulent velocity goes in the opposite sense. Variations of the equivalent widths and profiles of Hy and HS and of the equivalent widths of metallic lines in TJ Leonis were found by Malov and Vitrichenko (I964), who were led to temperature variations of IOOo°K, electron pressure variations up to a factor of 2 and radius variations up to about 30%. Kupo and Mamatkazina (I966) have studied the continuum of HD 2I 389, an Ao Ia star. In a number of K and early M giants of luminosity class III Deutsch has found time variations in the profiles of the central components of Ca II 3933 similar to the ones reported previously by him in many K-type supergiants; the doubly-reversed features, at high spectral resolution, exhibit a surprising degree of fine structure suggesting variable chromospheric

SPECTRES STELLAIRES

611

activity and sometimes the motion of a plage across the visible hemisphere, as the result of stellar rotation. The observations will be continued in a representative group of giants near

K5 III.

Deutsch and Keenan are continuing obtaining spectrograms in the blue and violet (20 Ajmm) that show systematic intensity anomalies in various atomic absorption lines and also in the bands of AlO. Griffin has prepared - publication is pending - a spectrophotometric atlas of Arcturus covering the wavelength region between 36oo and 88oo A, and at least comparable in all respects with the Utrecht solar atlas. A catalogue of lines (about 70oo) with wavelengths, equivalent widths, central intensities and identifications for A > 5000 A is well advanced. The work of cataloguing and indexing features was undertaken in collaboration with the present Mrs R. E. M. Griffin-Gasson, who has also investigated the atmospheric characteristics of Arcturus. The discovery by Griffin of the H and K emission reversals being variable in time, has been followed up by W. Liller observing H and K emissions in a number of stars with Griffin's photoelectric spectrophotometer. The Atlas of Arcturus has led to the discovery of [0 I] and [Fen] lines in Arcturus (Gasson and Pagel, I966). Griffin (I964a) found broad features at U 63I8, 6344 and 6362 A in Arcturus and in eleven other F5 to Mo stars which have been identified as calcium lines broadened by autoionization by Mitchell and Mohler who discovered them independently in the solar spectrum. The line at A 6362 has been studied by Griffin and Liller with the photoelectric spectrometer just mentioned. Griffin (I964b) has also given line identifications of Arcturus in the 8875 to I I 200 A region. F. K. Edmonds, Jr. will measure line blanketing in the I-2'5 p. region, using high-resolution Fourier transform spectroscopic observations obtained by P. Connes of the C.N.R.S. Bellevue Laboratories, in France, and in the U 35oo-88oo A region, using high-dispersion observations and equivalent width measurements of Griffin and Mrs Griffin-Gasson. Kubiak (I966) has discussed the influence of TiO bands on magnitudes and colours of M-type giants, by using high-dispersion spectrograms obtained by Preston. A detailed study of the spectrum of Procyon that comprises equivalent widths of I 52 lines in the wavelength range ,\,\ 3260-6610 A and line profiles of Hoc, H,S and Ca n-K, and the measurement of the continuous spectrum and of line blanketing has been published by F. N. Edmonds, Jr. in two papers, the second one in collaboration with F. D. Talbert (Edmonds, 1965; Talbert and Edmonds, 1966). Edmonds is also working on the photoelectric calibration of photographic equivalent widths of Procyon and Arcturus using the high-dispersion photoelectric scanner attached to the coude spectrograph at the MacDonald Observatory. F. Praderie is computing H lines in the atmospheres of AF-type stars. Sargent (I965a) suspects the presence of [N n] at 6583-6548 A in the spectrum of the Go Ia star, HR 8752, which would imply the existence of a highly ionized region around the star; the star displays Hoc and H,S emission suggesting superficial mass loss. Bonsack and Culver have continued their programme to determine, on high dispersion Mt Wilson spectra, wavelengths, equivalent widths and identification of the lines in the spectrum of the normal late G-type giant € Virginis; the measurements and reductions are already complete for 65oo lines in the wavelength range 4000 to 9000 A. Smak (I966a) has determined a new bolometric corrections scale for M-type giants by using the spectrophotometric data of Stratoscope II and the available six-colour data; and combined his results with recent determinations by Mendoza and Johnson.

612

COMMISSION 29

(g) Be and Shell Stars A desire to co-ordinate and stimulate work on the Be stars led Mrs Herman to propose in I96I at Berkeley the formation of a working group to which she is serving as chairman. A somewhat condensed and free English version of her report follows: 'In spectroscopy or spectrophotometry certain groups are particularly active. 'At La Plata, C. Jaschek, with the collaboration of B. Kucewicz, has continued his search for H oc emission in southern Bo-Ao stars brighter than 6·s magnitudes, and a list for the range Bo-Bs has been published (Jaschek et al., I964), while Kucewicz {I96S) has summarized the state of the search. C. and M. J aschek have described several southern Be stars and, in particular, have reported that in I96S HD 68 980 has displayed a sort of helium envelope with peculiar line profiles (C. and M. Jaschek, I96S; see also M. and C. Jaschek, I964). 'Miss Underhill has secured a number of spectra of 'Tauri at Victoria (October and December I964) and at Kitt Peak (January I966) and van der Wei, at Utrecht, has made a spectrophotometric study. In I964 the shell absorption lines are shaded towards the violet while in I966 the shading was towards the red. 'At David Dunlap, Heard has taken a series of spectrograms of r:p Persei at IO Afmm. 'L. Houziaux and Mme Y. Andrillat have undertaken the study of the infrared region, specially at Haute-Provence. A report on the measurement of the Paschen lines and those of 0 2 at 777I-S and at 8446, with the aim of determining the envelope electronic temperature and the oxygen abundance, has been published (Andrillat and Houziaux, I966b). 'At present, Houziaux is analysing the spectral variations of some 20 Be stars, between 7 and 8 magnitudes, observed in the last ten years. 'At Crimea, Boyarchuk and Pronik have studied the Hoc profiles in HD 2I7 oso, 'Tauri, r:p Persei, .p Persei, I I Camelopardalis and c Persei, finding that the wings are determined by radiation damping; they also reached the conclusion that the envelopes of the Be stars are oblated (Boyarchuk and Pronik, I964). They find that the Be stars are somewhat reddened relative to the normal B stars, a phenomenon probably caused by the envelope; in the case of X Persei and x Ophiuchi the Balmer decrement for the stars was found steeper than the Balmer decrement for the nebulae, apparently due to the large optical thickness of the Be envelopes for the Balmer lines radiation (Boyarchuk and Pronik, I96sa). 'In Italy, M. Hack and her collaborators (Hack et al., I964; Aydin et al., I96S) have observed 'Tauri from I96I through I964 and found that the envelope contracts and that the velocity of contraction has been decreasing. 'HD so I38 has been observed at Haute-Provence by Mme Doazan, who found pulsations of the envelope; she has applied Sobolev's method to such an envelope (Doazan, I96S) and has also measured spectra of HD 2I8 393 taken between I96o and I964. 'Miss Lacoarret (I96S) has studied the variations of the emission relative to the continuum in HD I68 9S7, HD I7I 406, HD I7I 78o, HD I7S 869, HD I77 648, HD I87 811, HD I9I 6Io and HD I74 237 and found periods of several years, while the VfR variations in HD I74 237 have a quasi periodicity of several days. She also discusses the characteristics of the envelopes and compares the results obtained by applying Miyamoto-Kogure, Pottasch and Sobolev's methods. 'Miss Delplace (I966) has been concerned also with 'Tauri and discussed the variation of the Balmer decrement in relation with the variation in radial velocities of the Balmer series. The problem of the periods of the spectral variations is also concerning Peton, who is studying HD 4S 9IO and HD 4I8o, and Mme Herman who has observed emission, present again in I964-6s, in HD I42 926; this star appears to have also a small metallic envelope. Leconte! is

SPECTRES STELLAIRES

613

investigating variations in f3 Canis Majoris stars in the hope of finding some relationship with the Be stars. At La Plata, C. Jaschek is undertaking the continuation of the Merrill and Burwell's catalogue and bibliography of Be stars.' Pik-Sin The (1964c, d; 1966a, b; The and Lim, 1964) has continued his search for Hac emission objects and it is rewarding to mention that Bidelman reports that the surveillance of the brighter Be stars carried on at Michigan for so many years by the late D. B. McLaughlin will be continued to some extent. Andrews and Breger ( 1966) have found that Achernar is a Be star, the brightest known. At Helwan, R. Goubrous is studying the He I lines in some shell stars. Mme Herman (1964) has confirmed the existence of double H absorptions in P Cygni, during certain periods and given a qualitative interpretation of the observed profiles in the framework of Sobolev's theory. Y. Andrillat (1965h) has spectrographically observed a potassium eruption in the B9e star 4 Herculis, a phenomenon which is analogous to that observed by Barbier and Morguleff in two dwarfs stars HD I 17 043 (dG6) and HD 88 230 (K7V) (Barbier and Morguleff, 1964). Y. Andrillat and N. Morguleff (1966a, b) have made a comparative study of the three stars known to display the phenomenon; they think that the phenomenon is not of atmospheric origin and plan to study its frequency by means of an objective grating and to continue investigating it in the case of the Sun. At Abastumani, Alania (1964) has found in the spectrum of MWC 84 that since 1932 there has been an increase of the order of seven times in the ratio of the emission lines at ,\ 3889 and H fl. Dolidze et al. (1965) reports a decrease in the Balmer jump of HD 190073 in 1964-65 and Dolidze, Apriamashvili and Jimsheleishvili have measured the Balmer jump in V425 Cygni. (h) Ca II Emission In Pretoria, Warner has observed over 200 G, K and M stars south of declination - 20° for H and K emission; preliminary results show a good correlation between emission intensity and space velocity but there are indications that different stars in a given moving group do not necessarily have the same emission intensity even when they have identical spectral types. Warner (1966a) has detected Ca II emission in Canopus, but this star does not obey the Wilson-Bappu relationship. Wilson finds that as one proceeds down the main sequence slow rotations set in very abruptly at B - V indices only o·oi magnitude from the onset of Ca II emission (near Fs V) and that Ca II emission is characteristic of stars that develop chromospheres, chromospheric activity, and 'winds' and that such activity causes a loss of angular momentum with concomitant rotational braking. He is making now a strong effort to study stellar chromospheres by rapid and accurate measurements of the central emission components of H and K. Wilson is also investigating the frequency distribution of the intensities of the chromospheric H and K emissions in maiq sequence K- and M-type stars. Since all the available evidence points to a close correlation between chromospheric activity and age for main sequence stars the frequency distribution should approximate the frequency distribution of stellar ages. Thackeray (1964) has reported the presence of abnormally strong Ca II emission in a young K star that belongs to the Sco-Cen association, and Metrevely (1966) has announced that the Ks star, BD + 28° 637, displayed strong H and Ca II emissions on December 24 1960 while they appear to be absent at other nights.

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COMMISSION 29 (i) Chromospheric He I

Vaugham and Zirin discovered He I A 10 830 in absorption in A Andromedae and have looked for the same feature in late-type stars. About 86 stars (Go to M6) selected from Wilson-Bappu list have been observed and about half of them show He I A 10 830 implying a hot chromosphere with temperatures exceeding 20 ooo°K. The strength of the line tends to increase with increasing Ca II H and K emission intensity, and it is violet displaced in virtually all supergiants as well as in some giants of luminosity class III. The He I A 10 830 feature has been found in at least one F star, namely, rx Canis Majoris.

(j) Metallic-Line and Peculiar A Stars The field of metallic-line and peculiar A stars has been a most active and a considerable amount of information have been obtained. Review papers have been prepared by Sargent (1964), M. Hack (1965, 1966a) and a catalogue of peculiar A stars has been published by Bertaud (1965). At La Plata, the Jascheks (M. and C. Jaschek, 1965) have analysed the information on the metallic-line and peculiar A stars and suggested that they represent a transient stage in a star's life; furthermore, on kinematical grounds they concluded that the metallic-line stars can not have gone through the giant stage. This conclusion finds support in the finding of an Ap star in I Persei by Kraft and in the presence of an Ap object in the o Velorum cluster. A review paper on the magnetic stars has been produced by Ledoux and Renson (1966). A preliminary determination of the magnetic field of rx 2 Canis Venaticorum has been tried at the Okayama Astrophysical Observatory (Unno and Kato, 1965). An important result is the discovery in f3 Coronae Borealis of the presence of a line due to lithium (Garstang, 1964) and of the possibility of variations in its intensity (Wallerstein and Hack, 1964). Hack and Faraggiana (1964) have discussed that discovery, and the results of the investigations of f3 Coronae Borealis and y Equulei at Merate. Adam (1965) has observed the magnetic variable HD 125 248 and found that the reduction in the amplitude of the magnetic field that was first noted by Babcock in 1953 is still continuing; the period, however, has remained remarkably constant over 17 years. P. Renson (1965) has determined the variations in radial velocity, luminosity and magnetic field and found the variation in magnetic field in function of phase presents an assymetry and resembles the luminosity curve as is true for other magnetic variables. Bruce Peterson (1966) has investigated the spectrum variables HD 124 224 and 56 Arietis and, from the equivalent widths of the variable lines of Si II and He I, has determined new epochs of maximum strength of the He I lines thus finding that the times of He I maxima coincide with those of minimum temperature determined from (B - V) and from Hy profiles as well as with the times of minimum light in V and minimum Si II. The intensity variations in Si II are very nearly in the same phase for lines that differ in excitation potential by 2·7 electron volts. These results conform better to a rigid rotator model than to a magnetic pulsation. The Ap star HD221 568 has been studied by Kodaira in the spectral range U38ocr']oooA and Kondo (1965) has analysed the continuous spectrum of 63 Tauri finding that Tel! ::::: 7600° = 7900° and log g ::::: 4·0. Also in Japan, Jugaku and Kikuchi are making a detailed spectrophotometric study of f3 Orionis on high dispersion Mt Wilson spectrograms that cover the range U31oo-88ooA; the spectrum of this star has been investigated by Svolopoulos (1966b) on McDonald spectra from 366oA to Hy line identifications and intensities are given and electron pressure and the amount of hydrogen above the photosphere have been determined. Osawa (1965) finds that the Ap stars may have ultraviolet excesses that become more pronounced if the colour indices are corrected for line blanketing.

SPECTRES STELLAIRES

615

A list of 3000 lines and their equivalent widths for y Equulei in the range ,\.\ 3730-6593 A has been published by M. Hack and M.S. Matthews (r965) by using material with dispersions of 2·8 to 4" 5Ajmm; only 6oo of these lines are unblended. Bidelman is planning to publish soon line identifications of a number of Ap stars studied on 2 Ajmm coude Lick plates, beginning with the manganese stars; the analysis of line intensities will be done as a second step. Bidelman is also studying a number of interesting stars two of which deserve mention at this time, namely, HR4487 (worked out in collaboration with J. Baumert) which appears to have very high abundance of yttrium and zirconium, and HD3473, which appears to be the only example of a Si-Mg star. Inspecting the spectra of most of the early-type stars investigated at the Dominion Astrophysical Observatory, Victoria, Bidelman has discovered a considerable number of new Ap and Am stars, and E. N. Walker (r966b) has recently published a list of 25 new Am stars. Other interesting results were reported by Bidelman at the r964 Utrecht Symposium on Abundances. Svolopoulos (r966a) have analysed the spectrum of the manganese star a: Andromedae, and given line identification and their intensities; electron pressure and the amount of hydrogen above the photosphere have been determined. Wehlau (r965) has studied the spectrum of the Ap star x Serpentis and also that of 73 Draconis (Wehlau r966), where he found large variations in the Kline; a spectrophotometric analysis of 73 Draconis is underway. John Rice is doing similar work on HD r74 650, where large variations in line intensities have been noted. 73 Draconis has been studied also by Galkin (r964) who has determined the variations with phase of the residual intensities of r9lines, has constructed curves of growth and determined the main atmospheric parameters. Renson (r966) finds that the magnetic variable HD844r is a spectroscopic binary with a period of ro6·27 days and that the published period of 2'!9632 for the magnetic variation is due to chance. Abt (r965) has measured 500 coude spectra of 55 normal A4-F2 IV, V stars and found no binaries with periods less than roo days, and r7 objects with periods larger than roo days; he suggests that all members of close binaries in that temperature range have metallic-line spectra, perhaps because the slow rotation found in close binaries is necessary to produce the unusual metallic-line spectra. In connection to the question of the rotational velocities of the Ap stars it is interesting to mention that E. N. Walker (r966a) in a recent discussion concludes that although some Ap stars may be seen pole on, Ap stars in general cannot be rapidly rotating normal A stars seen pole on. Baschek and Oke (r965) have shown that after deblanketing corrections are introduced, the metallic-line A stars in the Hyades cluster lie to the left of the main sequence in the colourmagnitude diagram, and Strittmatter and Sargent ( r966) find that the same is true for the metallicline stars in the Coma and Praesepe clusters, which these authors interpret as being due to the slow intrinsic rotation of the metallic-line stars and in agreement with the theoretical result of Roxburgh and Strittmatter that suggest that, at a given colour, more rapidly rotating stars will appear more luminous. Guthrie (r965b) has noted that there seems to be a preference for the manganese stars (it is not so among the silicon stars) to exhibit sharp lines; the difference between the silicon and the manganese stars may be related to the direction of the magnetic field relative to the axis of rotation. Buscombe (r965b) has measured equivalent widths of Hy and Ho for a large number of stars in IC239r including several peculiar A stars. H2

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COMMISSION 29

At Odessa, Komarov (1965) finds that, on the average, the electron densities in the atmospheres of the metallic-line stars do not differ from those of normal main sequence stars of the same hydrogen spectral class. (k) Subdwarfs Warner reports work in progress on several southern F-G subdwarfs. Two galactic subdwarfs in the field of the Large Magellanic Cloud have been discussed by Thackeray (1966a). D. S. Evans is working on a number of problems related to subdwarfs.

(l) Faint Blue Stars Greenstein is continuing the low dispersion studies of faint blue stars, in an effort to obtain a more accurate estimate of the percentage of white dwarfs at approximately the 17th magnitude. The mean Einstein gravitational red shift of 53 white dwarfs have been measured by Greenstein and Trimble as +51 km s-1, the mean for the DA stars being from +56 to + 62 km s-1• The derived mass of a helium core, about o·87[11®, is roughly consistent with the photometric radii deduced from luminosities and colours. A further extension of the spectroscopic and colourimetric work by Greenstein and Eggen is resulting in a third list of white dwarfs which will bring the total of completely observed objects to 202. Greenstein points out that the most interesting future problems will concern with hot white dwarfs with helium and carbon features and the possible effect of line blanketing on the colours of the red white dwarfs; for many of these no lines are visible but the radii deduced from the luminosity and the photoelectric colours are perhaps three times too large, it may be that they are hotter than they seem to be but their colours are perturbed by very greatly broadened lines, as Weidemann has suggested. A surprising number of the faint blue stars show composite spectra (hot star + G star) and one faint object Ton 120 had broad emission like a U Geminorium star or an old nova. The spectroscopic distinction between hot subdwarfs from very hot white dwarfs is difficult. The H and He line widths among subdwarfs vary by large factors. Subdwarfs occur with He I and He II lines nearly as wide as in white dwarfs of type DB and DO and the Stark broadening suggests a range in luminosity by a factor of 1000. It is likely that the majority of the halo blue stars classified as Bp (presumably horizontal-branch stars) are helium-deficient objects. Greenstein and Oke are continuing their study of horizontal-branch stars in globular clusters and have scanned 17 stars in M92 and several stars in M 15. The gravities obtained suggest that these stars may not all have the same mass. Bell and Rodgers (1964) have discussed the star L97-12; its spectrum appears continuous and the star may be dynamically related to the group of three ..\ 4670 objects discussed by Bell in 1962. Greenstein and Eggen's effort in finding new white dwarfs has resulted in the discovery of white dwarfs with small space motion that is of white dwarfs in the younger population indicating that extensive loss of mass can occur as evidenced by Sirius B. Greenstein and Eggen have studied correlation between colour and spectrum: the cooler white dwarfs that still show H lines lie near B - V = + 0·3 magnitude and U - B = o· 5 magnitude; the H lines are then extremely sharp, and deceptively weak, but this is not caused by low surface gravity alone but presumably by the depression of the ionization continuum, caused by high pressure. (m) Halo Population Stars Greenstein finds that the most single interesting star of the halo population yet observed is BD + 39°4926, a very metal-poor object with exceptionally strong neutral carbon and oxygen

SPECTRES STELLAIRES

617

Under the current interpretation of nucleosynthesis theory BD + 39°4926 may be an object which has formed early and has synthesized its own carbon and oxygen or it may be one with very abnormal, selective, early composition.

(n) Planetary Nebulae L. H. Aller has observed the nuclei of NGC4o and BD + 30°3639 with the Lick coude and measured them with the spectrum scanner; he has also observed, at 16A/mm in the photographic region, the central stars of NGC6543, NGC6826, NGC6891 and NGC2392. Fainter nuclei have been observed with the Lick nebular spectrograph at the 3-m reflector: the central stars of NGC6853, NGC6o58, IC3568 are essentially absorption-line objects while the nuclei of NGC6751, NGC69o5, NGC7o26 and IC1747 display interesting emission-line spectra of the Wolf-Rayet type. F. Bertola (1964) gives the list of emissions in the Wolf-Rayet type nucleus of BAC2o9, the first one which does not show lines due to C. C. R. O'Dell (1966) has studied M1-2 which were discovered and identified by Minkowski as a stellar planetary nebula; its spectrum may be explained as arising from a system of a G 2 star and a hot companion but we could be dealing, according to O'Dell with a very peculiar single star.

(o) Binary Stars

Orbital elements in the following Wolf-Rayet objects, y 2 Velorum (HD68273), HD 193928, HD186943, HD211853, HD193576 have been determined by Vainu Bappu and Ganesh (1967a, b). The period derived for y 2 Velorum is 78·5 days, which does not agree with the ones suggested by Sahade and by Gaposchkin (around 16 days). Azimov (1965) has carried out a study of ~e subgiants components of RS Arietis, S Cancri, RS Canis Venaticorum, SX Cassiopeiae, GC Cassiopeiae, U Cephei, UX Monocerotis, RY Persei and I Sagittae, finding that the electron densities and the spectrophotometric temperatures are higher than those of single subgiants of same spectral types. Spectrophotometric gradients, temperature and physical parameters of the two components of AR Lacertae were also determined (Azimov, 1966). Thackeray (1965a) has studied the spectra of the eclipsing system S Equulei and observed 'satellite' lines during eclipse probably due to gaseous streams; Thackeray's spectrograms are being investigated by Plavec. Smak (1965) has been able to measure lines of Na I that belong to the secondary component of XZ Sagittarii and made a direct determination of the masses of the two components. M. Spite-Lebon (1965) has determined the masses of the two components of x Draconis and Bartoli et al. have studied BV 382 Cephei. Sahade (1966a) has extended his study of the spectroscopic binary HD698 on the basis of new Mt Wilson material by Jugaku and Sahade and confirms that the lines of the secondary component are absent from the spectrum, reaching the conclusion that the star is another system in which the mass of the fainter component is the larger; emission at Hoc appears to arise from an expanding envelope around the system. The star (Sahade, 1966b) belongs to a group of systems with underluminous massive components (HD47 129, AO Cassiopeiae, V 453 Scorpii, V 448 Cygni, {3 Lyrae and possibly e Aurigae and W Crucis). One member of this group, V 453 Scorpii, has been discussed in detail by Sahade and Frieboes-Conde (1965b). An extensive study of the physical conditions in the atmospheres of HD47 129 and AO Cassiopeiae has been undertaken by Galkina (1965, 1967); special attention has been given to the behaviour of the He II 4686 emission. The wavelength dependence of the depth of the eclipse of e Aurigae during the 1955-57 minimum has been investigated by lvanova; in long wavelengths there is almost no variation with wavelength.

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The spectrum of f3 Lyrae in the visual region has been studied by Sahade and Hernandez (Sahade, 1966c); full details will be published later. A new series of spectra of the same region of f1 Lyrae are being obtained by Batten at Victoria. Feast (1967) has made a detailed spectroscopic study of the supergiant eclipsing system BL Telescopii, finding that the F-type primary has normal abundances though the r-process element europium may be overabundant; the secondary may be either a cool supergiant or a hot subdwarf ionizing a dense H II region. The spectroscopic changes during eclipse are interpreted as centre to limb variations of the primary. BL Telescopii is a 'run away' system and its present state is satisfied by the hypothesis that the secondary became of type II supernova 107 years ago. Further work on this system is in progress. B. F. Peery, Jr. has published his detailed study of VV Cephei where he has found spectroscopic information that was interpreted as evidence of material falling upon the B component. Data on the 1955-57 eclipse of VV Cephei and later data are being studied by Wright (1966a). Odgers and Wright (1965) studied multiple K-lines near the 1963-64 eclipse of CAurigae and Wright is analysing similar data for the 1965 eclipse of 32 Cygni. During the 1963-64 eclipse CAurigae has been also studied by Faraggiana (1965), and by Bardin and Prevot (1964a), while Scholz (1965) has measured the equivalent width of the Kline in 32 Cygni, and Faraggiana and Hack (1965) have compared the spectra of the K-type component of CAurigae, 31 Cygni and 32 Cygni. Sahade in collaboration with Hernandez, Fay and Cohen are carrying out a detailed investigation of 8 Librae based on all available spectrograms. At the David Dunlap Observatory Abhyankar obtained new spectroscopic orbits for S Coronae Borealis and HD2o8392. Fletcher (1966) made a new study of the orbit of 47 Andromedae. Heard determined spectroscopic orbits for the W U rsae Majoris star V 566 Ophiuchi (1965), for the double-lined Bo IV system HD217312 in the III Cephei Association (1966a), and for HD 131861 (1966b). Miss Northcott obtained spectroscopic orbital elements for the double-line binaries HD 15138 and 82780 and also for the double-line eclipsing system HD200391, for which Bakos has also obtained the photometric elements. At the Dominion Astrophysical Observatory orbital elements have been determined by Gutmann for C1 Ursae Majoris (1966a) and v Ophiuchi (1966b), by Thackeray and Tatum for HD 175 544 (1966) and for 31 Cygni by Wright and Huffman. The study of the spectroscopic binaries HD 208 947 and HR 88oo by the late R. M. Petrie, the latter with emphasis on the question of the apsidal motion, that were in a well-advanced stage at the time of his passing away, is being completed by Mrs Petrie. Bidelman et al. (1963) have called attention to the fact that HR4511 is probably a G-type supergiant spectroscopic binary. A. P. and C. R. Cowley (1966) have reported changes in the spectrum of HR8164 = Boss 5481 A which combines features of a sgM and of a B2 V objects. D. S. Evans has continued his spectroscopic study of the interesting triple system p Velorum.

(p) Miscellaneous Stars Webster (1966) has discussed some interesting emission line stars formerly classified as planetary nebulae; at least some of these stars seem likely to be symbiotic objects. Feast is studying coude of UY Centauri and several other similar stars. L. H. Aller and Th. Dunham, Jr. (1966) have described the spectrum of 7J Carinae in 1961 and, except for a few changes, there is an agreement with Thackeray's 1951 observations. Extensive work on 7J Carinae by Thackeray is reported under Commission 27. The same is true for the work done on RR Telescopii.

SPECTRES STELLAIRES

619

Objective Prism Work Objective prism surveys of the southern sky are being continued by Pik-Sin The and his collaborators. Among work in progress there are surveys for M stars in the direction of the south galactic pole, in Carina and towards the galactic centre. Helium-Weak Stars Greenstein, Sargent, Zirin and Heintze, Jugaku, Tsuji, Schadee and Boesgaard are devoting time to the problem of the apparently helium-weak stars. Metal- Weak Stars H. Bonel is attempting to discover at Michigan metal-weak stars on 10° objective prism plates; suspect ones are later observed with slit spectrographs. High- Velocity Stars BD + 37°442, discovered by Fehrenbach and his group, was studied by E. Rebeirot (1966); the star does not show H lines but does show strong ionized helium. Globular Cluster Stars Spectra of both the horizontal and the giant branches stars in NGC6397 have been obtained in Pretoria. Novae R. Goubrous (Helwan) has studied the behaviour of the H lines in Nova Herculis 1963 and Baschek (1964LZ) its near infrared spectrum; this has been followed by Y. Andrillat (1965a) from July 1963 to May 1965. Batten (1964) has published results from the spectra of Nova Herculis 1963 taken between February and August, and Wright and Bochonko are preparing an atlas of the H line intensities from plates of 6 and 1oAjmm. Nova Herculis 1963, of which Gotz (1965), with the Sonnenberg Schmidt, had secured a spectrum on 2 September 1962, before the outburst, has been the subject of several investigations. At Abastumani Alania and Popov (1965) have obtained a large number of objective prism plates between 25 March and 9 September 1963, deriving an expansion velocity of 1190 km s-1• B. Folkart et al. (1964a, b) have produced two papers where the results of the measurements of the Balmer line profiles and of the narrow emission and absorption lines in RS Ophiuchi 1958 are given. Cepheids Warner (1964) has published a list of wavelengths and identifications in the bright cepheid l Carinae which should be generally useful for supergiants of about the same spectral type. In Canada, Crompton has studied the spectrum of RU Camelopardalis which had been found by Demers and Fernie to have ceased its cepheid variation. Alania (1965) have found that while the variations in spectral type of the short-period cepheid DX Delphini go from AS to F8, the spectrophotometric gradient changes a little more that what it would correspond to the range in spectral types. More information on cepheids will be found in Commission 27 report of the Committee on the spectra of variable stars. Symbiotic Stars M.P. Fitzgerald, N. Houk, S. W. McCuskey and D. Hoffieit (1966) give a preliminary line identification list of M Hoc 382-116 which appears to be similar to a symbiotic variable, spectrum wtse.

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Long-Period Variables A review article on the long-period variables including the discussion of some spectroscopic problems has been published by Smak (1966b). Keenan, Deutsch and Garrison are undertaking a programme to observe the intensities of selected atomic lines and molecular bands in a number of the brighter Mira variables over several cycles and compare them with simultaneous photometric data obtained by other observers; the molecular bands under particular study include AIO ..\4842 and YO ..\6132. Smak (1964) has discussed the effect of the TiO bands on magnitudes and colours of the Mira type stars as well as their position in the Mb 01 - Te diagram. Alania (1966) has completed a study of the continuous spectrum of AC Herculis; at ..\..\4ooo-6oooA the colour temperature varies from 4900° to 68oo 0 • (q) Miscellaneous studies

Rachkovskaya (1967) at Crimea has found that the spectra of the Ia-type variable stars AB Aurigae, V 568 Cygni and o Herculis do not differ from the spectra of normal stars of same spectral type. Variations with time of the intensities of the emission and absorption components of the H lines were found in the spectrum of AB Aurigae. Work on the MC Objects Hutchings (1966) has measured Hy equivalent widths for many stars in both Clouds and Thackeray (1965b) has studied spectroscopic changes in S Doradus. Infrared Studies

Moroz (1966) has observed infrared spectra (1 to 2·5 p.) of 19 A1-M7 stars. Strong absorptions at 1·5 p. and at 2 p. which appear to be due to wings of stellar H 20 bands, were found in the spectra of the long-period variables o Ceti, R Aquilae and X Ophiuchi at light minima. A large number of fine absorption details due to CO were found in the spectra of K2-M5 giants. The energy distribution of red giants has a maximum at 1·6 p., apparently due to the H-and H 2-ions. Becklin at Caltech is determining infrared energy distribution out to 4P- for several infrared stars including an infrared object in the Orion Nebula that appears to have a blackbody temperature near 6oo°K. McCammon, Neugebauer and Munch have obtained spectra of some of the extremely red objects discovered in the Infrared Sky Survey carried out at Mt Wilson. Among the interesting features found let us mention the sharp discontinuity at..\ = 1"745 p. in theN-type stars Y Canis Venaticorum and U H ydrae. Neugebauer and Munch have observed the spectrum of x Cygni with the coude 100-inch and a PbS detecting system. Rotation

At Crimea, Boyarchuk and Kopylov (1964) have compiled a general catalogue of rotational velocities of 2558 stars, reduced to the Slettebak system. The catalogue is sufficiently complete stars brighter than magnitudes. for E. N. Walker (1965) has studied the variation of axial rotation with spectral type for main sequence stars within the range B9 to As, and reached the conclusion that there is a preferential rotational velocity for stars of 2m®; the material comprises 633 stars. Slettebak (1966a, b) has continued his studies on stellar rotation by investigating axial rotation in 56 later Be stars; the frequency distribution of rotational velocities of 42 of those stars suggests that all are rotating with an equatorial velocity near 350 km s-1 but have their

Os-Gs

s·s

SPECTRES STELLAIRES

621

rotation axes randomly oriented in space. Further, a comparison was made between the largest observed rotational velocities for stars of spectral types 0 9·5-Fo and the computed equatorial break up velocities for stars of corresponding spectral types; and the region of minimum difference between the observed and the computed velocities is approximately that occupied by the Be stars. Slettebak and Wright have estimated rotational velocities in 77 A-type stars near the north galactic pole and are carrying out studies of axial rotation in the Scorpio-Centaurus association and in h and x Persei. G. W. Collins II (1965) has extended and refined earlier work on the continuum emission from an early-type rapidly rotating star finding that a grey atmosphere is a moderately good approximation in the visible and a rather poor approximation in the ultraviolet where a variation up to I· 4 magnitudes in the colours, due to the effects of rotation, may be expected. Collins and Harrington (1966) have computed H,8 profiles for rapidly rotating stars taking into account the effects of gravity darkening, limb darkening and shape distortion. In the range Bo V-B5 V considerable variation in shape with rotational velocity was found for the earlier types, while markedly variations of equivalent widths with rotation was found for the later types; calculations of H y profiles are near completion. Andrews has measured the rotational velocities of B stars in IC2391, IC2602 and in the Scorpio-Centaurus association and was able to show that the faster rotators have the smaller Hex strengths, thus mimicking stars of higher luminosity. Deutsch has examined the available statistics of rotational line widths at various spectral types along the main sequence and concludes that these statistics are fully consistent with a Boltzmann-type law for the distribution of angular momenta of stars. Deutsch and Kraft have accumulated some line-widths statistics for main sequence F stars. Kraft and Wrubel have shown empirically that, at a given B - V, the slow apparent rotators of the Hyades show an ultraviolet excess relative to the fast rotators for spectral types between A8 V and F5 V, the amount of which is fully predicted by the change in surface brightness and effective temperature as computed by Sweet and Hogg. The implication that appears to result is that mild ultraviolet excesses for field F stars cannot be interpreted directly as evidence of metal deficiency unless the rotation is average to large for that spectral type. Kraft has made an extensive study of v sin i in function of Mv for the stars of galactic clusters. Kraft, C. Anderson and R. Stoeckly have redetermined the rotational velocities for stars in the Pleiades. On the basis of this work and the work of Abt and Hunter the suggestion is made that even after stars arrive on the main sequence, after gravitational contraction, there is still some slowing down of apparent rotation. Baum, McGee and Kraft have made a study of rotational velocities for Praesepe stars using an electronographic image tube to obtain spectra of stars fainter than Mv ,....., + 3· The rotational velocities of all stars of very young I Persei (ex Persei) group down to F5 V were studied by Kraft. In a rediscussion of the rotational velocities of three T Tauri stars previously studied by Herbig, Kraft finds that angular momentum probably is not conserved for these stars as they contract to the main sequence along their Hayashi tracks. Spectrograms of stars of NGC2264 are obtained to check this point. Kraft has studied in more detail the rotations of main sequence stars later than F5 V and finds a systematic tendency for higher rotations up to 25 km s-1 to occur among the younger dwarfs having K emission than among older dwarfs without K emission. Angular momentum among stars on the main sequence appears to decline with a time scale like that of the decay of stellar chromospheres.

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Analysing Slettebak's measures of v sin i, Deutsch can distinguish, near Ao, two groups of stars, one the 'Y' (or young population) which comprises about 8o% of them, while the remaining 20% constitute the '0' (old) population. According to Deutsch, the latter, sharp line objects, are on the main sequence for the second time and are metamorphs of originally massive main sequence stars that have lost substantial mass and angular momentum while in the red giant stage. The Ap stars- and similarly the Am stars- are the slowest rotations of the 'Y' population. Walker and Hodge (1966) have measured equivalent widths and half-widths of the He I lines .\4388 and .\4471 as well as rotational velocities for 425 09-B5 stars, and Deeming and Walker (1966) have made a statistical study of these data and also of Hy-measures, and were led to propose a model in which atmospheric turbulence is generated in the equatorial region of a star as a result of rotation.

Turbulence Conti and Deutsch (1966) have established that the weak-line and strong-line characteristics observed in stars result principally and directly from differences in turbulence and that the weak-line characteristic is very probably just the result of the systematic decay in the microturbulence of a star in a time scale that is short compared to its life time on the main sequence. Deutsch suggests that microturbulence decays for the same reason that chromospheric activity decays. 0. C. Wilson has recently shown that this is due to a diminution of the non-radiative energy flux generated in the hydrogen convection zone: this flux excites microturbulence, chromospheric activity and a quasi-steady mass loss similar to the solar wind. Conti and Deutsch have shown that in the disk population turbulence differences from star to star will change the line strengths in a way that produces ultraviolet excesses or other colour anomalies. In short, turbulence may be more important than abundance anomalies in producing unusual colours. In agreement with the above results, in a study of a cepheid of large light amplitude and weak lines, Abt et al. (1966) have found that the lines are weak because of low microturbulence rather than low abundances. This arises the question whether microturbulence in stars depends on the location of origin in the Galaxy. Bonsack and Culver (1966) have determined widths at half-depth and equivalent widths of a selection of weak lines of neutral vanadium in the spectra of 58 stars of types G, K and M that include all luminosity classes, and found that the profiles of the weak lines in K stars are dominated by the motions of large elements of gas and that the velocities of these elements are correlated with stellar luminosity in the same way as are the phenomena at higher levels in the atmosphere which determine the widths of the K line emission and H a absorption. By comparing the profiles and intensities of the lines with a theoretical model that represents the continuum spectrum, Underhill and de Groot (1964) concluded that the strongest lines in 10 Lacertae are enhanced by microturbulence, evaluated in 15 km s-1, and that the He II intensities are influenced by turbulence and therefore are not good indicators of helium abundance. Bell and Rodgers (1965) discussed turbulent velocities in the atmosphere of the supergiant 8 Canis Majoris from equivalent widths, half widths and central depth measurements of the Fe I and Fe II lines. Microturbulence is of about 12 km s-1 for lines of all excitation potentials. Macroturbulence is also independent of excitation potential but probably depends on equivalent width. Kopylov (1965) has determined the microturbulent velocities in the atmospheres of 68 06-Bs type stars by the curve-of-growth method and the dependence of the microturbulent velocities with spectral type was analysed in a semiquantitative manner. A detailed analysis of

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the physical conditions in the atmospheres of 19 0-type stars have been carried out by R. N. Kumaigorodskaya (1965a, b) who found that the large scale motions exceeds those derived through the curve-of-growth method by a factor of 2 to 3· Bell and Rodgers have also studied turbulence in the cepheid f1 Doradus (cf. Commission 27 report of the Committee on the spectra of variable stars), and Boyarchuk and Pronik (1965b) have found correlation between the turbulent velocity and the character of the H emission in the spectrum of ' Tauri. II. ABUNDANCE DETERMINATIONS

Just before the Hamburg General Assembly, a symposium on 'Abundance Determination in Stellar Spectra' was held in Utrecht. The proceedings of this symposium (IAU Symposium No. 26) have just recently been published as well as the proceedings of a conference on stellar evolution sponsored by the NASA Institute for Space Studies and held in New York in November, 1963, part of which deals with abundances (Stein and Cameron, 1966). A recent survey article by Cayrel and Cayrel de Strobel (1966) deals with many of the current problems.

(a) Early-Type Stars Warner (1966b) has used his calculated /-values of Fe III to determine the iron abundance in y Pegasi (B2 IV) using the equivalent widths measured by Aller and Jugaku in 1958 and an approximate solar abundance was found. D. H. McNamara and Mrs L. Sivers are investigating the titanium abundance in the B3 star HD37 058, the spectrum of which displays very strong Ti II lines at .:\3759 and 3761, lines which are absent in other sharp-line stars of comparable spectral type. L. H. Aller and J. Ross are concerned with A and B stars of peculiar chemical compositions and are reanalysing their vast high-dispersion material by using a better method of reduction of the plates and improved model atmospheres. Preliminary abundance analysis was carried out for v Herculis, x Lupi, cp Herculis, ' Coronae Borealis, HR8349, HR 7664, -r Capricorni, HR687o and 'Herculis. In all these objects, except for cp Herculis, for which no Sr, Y or Zr data are available, it is found that Sr, Y and Zr are greatly enhanced in abundance by factors ranging from 10 to 1000. Ti and Mn appear to be enhanced in v Herculis and the binary star x Lupi-which has been studied in detail by Robert Wolfe-appears to be a heavy-metal star with prominent Hg, while in cp Herculis, Sc and Cr appear to be enhanced whereas Fe is nearly normal. Reanalysis is essentially completed for ' Coronae Borealis in which both Mn and Fe are substantially enhanced; Ti and Fe are enhanced by factors of 5 and 10 in the phosphorus star HR8349 and HR 7664. Titanium may be also overabundant in -r Capricorni, whose spectrum is characterized by many weak lines. A remarkable star on the list is HR687o = HD 168733 which has strong lines of chlorine; Fe which appears as Fe I, Fe II and Fe III, is enhanced about a hundred times, while titanium and strontium are increased by more than a thousand times over normal abundances. ' Herculis appears to have normal abundances although sulphur may be enhanced. Conti has studied five extremely sharp-line A stars and found abundance differences that suggest relations with the 'metallic-line' stars of lower temperatures. Buscombe is studying coude spectra of southern OB stars with the aim of detecting possible differences in the He/H ratio, and is analysing x Octantis (B8 V) and K Eridani (B5 III) for abundances. Hutchings is determining line intensities and Hy profiles of several members of NGC6231 and the results discussed in terms of model atmospheres and in conjunction with photoelectrically measured line intensities at Cambridge.

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Henry and Mihalas (1964) have made an extensive study of magnesium in many 09 V to A2 V stars, and find N (Mg)/N (H) = 2·2 x 10-4 with little scatter. This abundance is an order of magnitude greater than the solar value. In 10 Lacertae, Underhill and de Groot find a magnesium abundance lower by a factor of 10 than that of Henry and Mihalas. Underhill is trying now to determine from Fe III the iron abundance in 10 Lacertae. An unsuccessful search for deuterium in B, A and F stars was carried out by Peimbert and Wallerstein (1965b); in some cases the upper limit is below the terrestrial value. (b) Helium-Weak Stars The important discovery of He 3 in 3 Centauri A by Sargent and Jugaku has been confirmed by Rodgers and Bell (1964), and from the line displacements of the helium lines in several B-type spectra, Gutmann (1966c) has concluded that He 3 is almost as abundant in p Leonis as in 3 Centauri A. The spectrum of 7J Leonis has been analysed by J. Hardorp (1963). Bidelman (1965) has called attention to the variation with time of the strength of the helium lines in HD 125 823 ( = HR 5378), a member of the Scorpio-Centaurus association; this variation has been confirmed by Thackeray (1966b). The Jascheks (1967) have found Ga II in the star which they class with the helium-weak stars, 3 Centauri A, IX Sculptoris, 36 Lyncis and IX Cancri. The discrepancy between the spectral types of these objects, classified on the basis of the He lines, and their UBV colours is being used by the J ascheks at La Plata to search for more members of the group. B. N. G. Guthrie (1965a) has studied some Be stars (HD37051, IX Sculptoris, 20 Tauri and 36 Lyncis) with weak He I lines for their intrinsic colours and strong Sc II, Ti II, Cr II, Fe II and Sr II and also HD 175156 where lines of He I, C II, N II, Mg II, Si II, Si III, S II, Ca II, Ti II and Fe II were identified and reaches the conclusion that the five stars are probably rapidly rotating stars of normal chemical composition viewed pole-on, the line strengths appearing abnormal only because the effective temperature and surface gravity are much higher at the pole than at the equator in rapidly rotating stars.

(c) Hydrogen-Poor Stars Several hydrogen-poor, or helium, stars have been subject of investigation. A review article on these stars has been written by M. Hack (1966b). Hill ( 1964, 1965) has analysed HD 168476, HD 124448 and BD + 10°2139 and the abundance of He, relative to the total mass of the atmosphere, corresponds to that expected for total H exhaustion. The abundance of 0 is only i- to ! normal while C and possibly also N e and N are overabundant; other light elements appear normal. In HD 168476 the elements of the iron peak appear to be ten times overabundant but the lines of these elements may be formed in an outer cool shell. HD96446 has been analysed by Cowley et al. (I963) on the basis of high dispersion spectra, and a ratio of HfHe ,..._, o·38 was found, line identifications of this star, which include 79 lines attributed to Kr II, have been given by Buscombe (1965a). Warner has observed the four known H-deficient stars with constant brightness and is carrying out an abundance analysis. (d) Metal-Weak Stars M. Spite-Lebon (1965) has made a differential study, relative to the Sun, of x Draconis A, a metal-weak star and the brighter component of a 28o-day period spectroscopic binary, where she found that most of the elements are deficient by a factor of 2 (except calcium, manganese and barium) and that the age of the stars is the same as that of the Sun. Mme Spite-Lebon has determined the masses of the two components.

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(e) Metallic-Line and Peculiar A Stars A spectrophotometric investigation in the near infrared of metallic~line stars has led Praderie (1965) to the determination of the abundance of 0, Nand Mg in those objects. For the stars 63 Tauri, w Tauri and T Ursae Majoris theN abundance seems to be somewhat higher than in the Sun, while 0 appears to be relatively slightly underabundant, in agreement with an earlier result of Sargent and Searle. In Pasadena, Subhash Chandra has examined the spectra, with particular attention, to the region AA310o-3700, of many relatively sharp-line Ap stars and found that strong lines of Be II are present in several Si-,\4200 stars as well as in most Mn stars and that a strong correlation appears to exist between the intensity anomalies in Ca II and Ba II and Mn II and Y II. Less pronounced correlations exist between other pairs of elements and in a number of Ap stars Chandra finds chromium lines (but not iron lines) that lie far below the flat part of the curve of growth in normal stars of the same temperature, and concludes that many abundances are really highly anomalous in Ap atmosphere but that the most conspicuous differences among the Ap stars may result simply from differences in temperature. Conti (1965a) has studied the abundances in five metallic-line A stars in the Hyades relative to normal F stars in the cluster using semi-empirical model atmospheres. The abundances differences appear to be real: he finds calcium to be deficient, some elements lighter than iron underabundant and some heavier than iron overabundant. Conti (1965b) has also made a high dispersion spectroscopic survey of the sharp line early A stars brighter than 5'5 magnitudes and accessible from Mt Wilson and found that nearly half of them have the properties of the metallic-line stars that had been previously identified only in stars as early as As. Among the stars that Conti finds that are metallic-line objects let us mention Sirius and 68 Tauri. Most of those stars are spectroscopic binaries. Conti's investigation have been extended, in collaboration with S. Strom, also to eight sharp-line early A stars in the Pleiades cluster, several of which appear to be metallic-line objects of early type. K. Kohl (196¥) with the help of non-grey models have determined the abundances of 27 elements in Sirius and the conclusion is also that the star is a metallic-line object; he (Kohl 1964b) studied the spectrum of Sirius from 3100 to 8863A. Sirius has been also studied by Warner (1966b) who rediscussed the abundances of the iron group with the use of a semiempirical model atmosphere; Warner has concluded that actually Sirius has some of the characteristics of a metallic-line star but the overabundances are less extreme than previously reported by others. F. Praderie is making a detailed analysis of the metallic-line star { Lyrae A. Searle and Sargent (1964) have compared Si II and Mg II lines in 31 Ap and five normal A- and B-type stars. These lines behave in a very similar fashion, are not sensitive to temperature or electron pressure changes, and therefore should indicate real abundance effects. Among the manganese stars they find silicon and magnesium normal. The stars of the manganese group were found by M. and C. Jaschek and Gonzalez (1965) to have strong overabundances of Mn, Yt, Ga and Hg; He tending to be weak and Sr and Ti being generally overabundant though varying from star to star. Two stars of the ',\4200' group (HD17365o and 192913) were found to be iron-rich and also to have large overabundances of Si, Cr and Hg (M. Jaschek and Z. Lopez Garda, 1966; A. D. Thackeray, 1966b; M. Jaschek, Z. Gonzalez and C. Jaschek, 1965). The' ,\4200' stars, HD 34 452, v Fornacis and 41 Tauri as well as the Cr-Eu star HD 2453, 25354, 42616, 71866 and 135297 are under investigation. Cl II has been found in HD34452 (M. and C. Jaschek, 1967) and P II in HD6822 (M. and C. Jaschek, 1964). A review of these investigations shows (1965b) that besides general group characteristics there are individual composition anomalies among stars that occupy nearby places in the two colour diagram, implying that there is no close correlation between colours and abundance anomalies.

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Mrs Z. Lopez Garcia (1966) studied y Capricorni on the basis of high-dispersion material from Mt Wilson, and determined atmospheric parameters and found overabundance of Ti, Cr, Fe, Co, Sr, Y, Zr, Ba and La, underabundance of Sc and practically normal abundances of Mg, Ca, Mn and Ni. An investigation of the same star made earlier by Faraggiana (1964) on intermediate dispersion plates, had indicated an overabundance of some metals. The abundances in the Mn star 53 Tauri has been revised by Warner (1965a) by using new ]-values, and a new determination of the chemical composition of the star has been made by Guthrie (1966), by differential curve-of-growth method with a. Lyrae as the comparison star, by using groups of lines of similar mean excitation and ionization potentials and wavelengths. It was found that Mn is overabundant by a factor of about 12, while Mg, Ca, Sc and Fe are deficient and the abundances of Si, Ti, Cr, Sr and Zr are about normal. The peculiar A star HD89822 (=HR4072) found by Guthrie to be a double-line spectroscopic binary, was analysed by the same investigator from the point of the chemical composition resulting that for the brighter component Si, Mn, Sr and Y are overabundant by factors of about 20, 4, 90, and 200, respectively, while Sc is deficient by a factor of at least 5 and the abundances of Mg, Ti, Cr and Fe are about normal; the relative abundances of Ti, Cr, Fe, Sr and Y are similar in the two components. Baschek (1964b) has determined the Na abundance in peculiar and metallic-line stars. For the A42oo-Si II stars, silicon is overabundant by factors of 10 to 6o and the ratio of silicon to magnesium is 6o times the normal value, while the C II and He I lines are very weak suggesting abundance deficiencies. An analysis of the manganese star 53 Tauri by Aller and Bidelman (1964) indicates that manganese and gallium are very overabundant, strontium, yttrium and zirconium are somewhat enhanced. L. H. Auer et al. (1966) have carried out a fine abundance analysis of 53 Tauri where they find that all of the metals lighter than titanium have normal abundances, and that He is underabundant by a factor of 5· From titanium onward, the elements show large overabundance factors, except for iron and chromium, both of which are normal; manganese is found to be 120 times overabundant. Auer (1964) finds, in an analysis of 10 Aquilae, that europium, strontium, magnesium, manganese and cobalt are overabundant, while aluminium, scandium, zinc and barium are underabundant. Searle et al. (1966) have studied the iron-peak elements in 18 Ap stars. In manganese stars MnJFe is 6 to 6o times normal. The chromium to iron and titanium to iron ratios are abnormal and vary from star to star. In silicon-rich and oxygen-poor stars the ironpeak elements are in normal relative abundance. Wright (1965) has begun analyses of the Ap stars 1r1 Bootis, HR4072 and 49 Cancri. The star 1r1 Bootis has strong lines of Ga II and Hg II. Yttrium is strong, but ionized lines of the iron group and rare earths are weak. The Aop star~: Ursae Majoris has been analysed by Leushin (1965) at Crimea and physical conditions and relative abundances were determined, Ca deficiency being detected. Log g was found to be 3·5 from the H,B and Hy line profiles while the mass-radius relation gives a value of 4"4· Yamashita ( 1966) has made an abundance study of the peculiar K-type star 37 Comae Berenices and compared its spectrum with those of the K giants x and ifJ U rsae Majoris; the abundance of Carbon in 37 Comae Berenices was found to be one-seventh the value found for the comparison stars. In Pretoria Warner has obtained high dispersion spectra of a number of Ap and Am stars and abundances are being derived. Hyland has in progress in Canberra a large programme of high dispersion spectroscopy and spectral scans of Ap and metallic-line stars in clusters and in the general field.

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A search for deuterium in magnetic stars (using the H a. transition) by Peimbert and Wallerstein (1965a) was negative. They give upper limits for DfH of 7 x Io-4 to 4 x Io- 5• e. I. Barium Stars All the stars of this group have been studied by Warner (1965b) who finds carbon overabundant by factors 3 to 5, in agreement with previous determinations. The overabundance of heavy elements appears to be well explained by the s-process in nucleosynthesis. Danziger (1965b) has analysed the Ba II stars HD n6713 and HD83 548 finding somewhat greater overabundances. Among the light elements discussed by Warner and Danziger there is evidence for overabundances of Na, C and N. Warner has also derived absolute magnitudes from the H and K emission widths (Wilson-Bappu effect). It is of interest to note that the problem raised by the large overabundance of Pr, an rprocess element, in barium stars seems to have been solved in a theoretical discussion by Reeves (cf. R. Cayrel and G. Cayrel de Strobel, 1966). In Japan, Nishimura is analysing the star HR 774 with the curve-of-growth method. e.2. The Holmium Star HD 101 o65 Przybylski (1966) has continued his work on the strange rare-earth star HD 101 o65, where most rare-earth elements are very overabundant (by factors of 100 to 4000) although no evidence has been found for ytterbium. The question of lithium in this star has been considered by Warner ( 1966c) and is mentioned in the section on lithium abundances in stellar atmospheres; he is using H a. profiles together with model atmosphere calculations to establish the absolute magnitude of the star. Przybylski who is studying HD9996, a similar star to HD 101 o65 but not such an extreme case, notes the possibility that HD 101 o65 should be considered as a metal-poor star.

(f) Late-Type Stars F. K. Edmonds, Jr. and S. Strom will do a fine analysis abundance determination for Procyon; Strom will furnish a non-LTE, line blanketed model atmosphere for the star. G. Cayrel has determined the physical parameters and chemical composition of the atmospheres of seven stars of early K-type, as well as those of a comparison star (€ Virginis). Two of the stars are main sequence objects-HD190404 and HD219134-which were observed to try to solve the problem posed by 0. C. Wilson as to whether the scatter observed on the colourspectral type diagram for stars later tha G 5 is due to chemical composition differences; the conclusion of Mrs Cayrel's study is that the two stars have the same chemical composition but that microturbulence is much larger in HD219 134 than in HD 190404 and this effect plus the temperature difference found to exist between the two stars, explains their colour difference (B - V = o·82 for HD 190404, and B - V = 1·02 for HD219 134; 0. C. Wilson's spectral types for the two stars being almost the same). The rest of the stars investigated by Mrs Cayrel were giants of luminosity class III and II. A pair of them HD48781 and HD94264, classified as 'strong line' and 'weak line' stars, respectively, suggested that the chemical composition as well as other atmospheric parameters were identical in the two stars but microturbulence was smaller in the weak-line star. HD6437, is metal deficient by a factor of 2 to 3; HD 6833, a typical halo object, is less metal deficient (on the average by a factor of 8) than the three halo K giants previously analysed by Greenstein and his collaborators, but metal deficiencies are not uniform from element to element; HD 35 620 has an abnormal spectrum and yielded a slight underabundance of the metals by a factor of 3· In HD6833 fairly strong interstellar D 1 and D 2 lines were found. Baschek et al. (1967) have carried out a quantitative analysis of the spectrum of the F8 V star f1 Virginis, which has been described by Namba (1964) from ..\3900 to ..\682oA.

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Climenhaga (1965, 1966) has continued his studies of the C12/C13 abundance ratio in late-type stars, and, from a study of the red bands, has determined the ratio for 19 Piscium, DS Pegasi and Y Canum Venaticorum. Wright (1966) has obtained high-dispersion spectra for the G5 stars, 51 Pegasi and 20 Leo Minoris, for an abundance study. At Canberra, Pagel has secured coude spectra in the blue and red of a number of solar-type stars for which six-colour and other photometric data indicated that the metal abundance might differ from that of the Sun; these stars are a Centauri A and B, p Pavonis, HD I914o8, a Phoenicis, p Tucanae, 82 Eridani and 8 Pavonis); abundance analysis are in progress. Conti and Greenstein, in co-operation with Spinrad, Vardya and Wallerstein have made an extensive study of 0 abundance using the [0 1] lines at,\,\ 6300 and 6363. The observational data show a steady decrease of [0 1] line strength with advancing spectra type and increasing luminosity; it is strongest in high velocity stars, which have a moderate metal deficiency. Koelbloed has obtained at Mt Wilson spectra of G and K dwarfs, giants and supergiants for chemical abundance analysis. Greenstein's programme on S-type variables has been supplemented with the observation of high-dispersion spectra of the bright, non variable S star, HRuos. Isotope ratios are being investigated by Schadee who has computed the shifts that according to theory should show the molecular bands. He is concerned at present with the search for Si28 and Si 30 in HR 1105 and for Zr isotopes in R Andromedae. Wyller (I966) has measured wavelengths of lines in the CN bands, particularly in the near infrared, to discover regions where the C12JC13 ratio can be measured. In five carbon stars he finds this ratio to vary from 2 (in Y Canis Venaticorum and WZ Cassiopeiae) to I I ; the equilibrium ratio for the CNO cycle being 3·4. Wyller suggests that C13 in carbon stars is partially synthesized by spallation and processes of neutron irradiation either in the atmosphere of Wolf-Rayet stars or in the carbon stars themselves. Schadee is studying the ultraviolet SiH bands in order to determine if the Si 28 JSi 30 ratio can be obtained. The same kind of analysis of the ZrO bands is used to determine how the Zr isotopes can be measured. Mrs Locanthi has studied ZrO in R Andromedae and in V Cancri. (g) Giant and Supergiant Stars

F. Spite (I964) has dealt with the method to approximately evaluate the metal abundances in some giant stars from low dispersion spectra by measuring the central depths of H y and of Ca 1 4227. Przybylski (1965) has made an abundance analysis of HD33579, a giant in the LMC. Zeinalov and Kopylov (1966) have made a detailed investigation of the physical conditions of the atmosphere and abundances in the supergiant 7J Leonis. At Kiev M. Ja. Orlov (1966) has analysed the spectra of the M-type supergiant f.L Cephei (A 425o-66ooA) and determined physical conditions in the atmosphere and abundances and discussed the relations between some parameters of the M-type supergiants. At Crimea, M. E. Boyarchuk (I965) has studied the spectrograms of p Cassiopeiae, () Canis Majoris and y Cygni and found that in the atmosphere of p Cassiopeiae the abundance of the light elements was smaller and that of the heavy elements greater than in the atmospheres of the supergiants () Canis Majoris and y Cygni. A. Underhill is attempting to determine from Fe III the iron abundance in y Pegasi and p Cassiopeiae. (h) Subdwarfs

Danziger (I966) has carried out a curve of growth analysis of the bright southern late-type subdwarfs y Pavonis and p1 Reticuli. The results, which are compatible with s-process theory,

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indicate that the metals lighter than nickel are underabundant by o·7 (in the logarithm) in y Pavonis and by o·4 in p1 Reticuli while the underabundance of carbon is greater (1·3 in y Pavonis and o·8 in p1 Reticuli). The relative abundance of Mn to Fe is normal in both stars but the heavy rare-earth metals are more underabundant than the iron group. (i) High- Velocity Stars

Koelbloed has studied abundances in two weak-line stars of very high velocity, HD z665 and HD6755 on Palomar spectra taken by Greenstein. HD 116745, discovered by Fehrenbach and Duflot, was found by Sargent (1965b) to be metal-deficient; the star must be highly evolved. Metal deficiency attains a factor of 40 in Wilson 10367 (LPM661) as it results from the study made by Baschek (1965) in the ultraviolet and the blue. Sargent et al. (1964) find a normal chemical composition in 7 Sextantis; earlier the star was supposed to be overabundant in helium and carbon. At Pretoria, Peat has obtained spectra of six southern high velocity K giants in the 5ooo66ooA region and a detailed analysis is in progress; the low velocity K giant oc Indi was observed as a comparison star. Kodaira (1964) has determined the structure and chemical composition of HD 161817.

U) Globular Cluster Stars Searle and Rodgers (1966) have discussed 86Ajmm spectra of horizontal branch stars in the globular cluster NGC6397, finding that the metals are deficient by a factor of 100 while helium is deficient by a much smaller amount. They estimated the masses of these stars as 1·3 9)1®· Sargent (1965b) has studied Radcliffe spectra of HDu6745, the bright F-type member of w Centauri, discovered by Fehrenbach and Duflot. The star was found to have the same Hy

profile and hence the same temperature as the normal F5 III star HD 113 537, but to be deficient in Ca and Sr by a factor of between 25 and 6o. Because of large number of Ti II lines in its spectrum, Sargent suggests that something more complicated than a simple general metal deficiency will have to be postulated for the star. Observations of the horizontal-branch stars in globular clusters by Munch and of spectroscopically similar brighter objects in the galactic polar caps by Greenstein do not necessarily support the suggestion from theoretical work that the early He/H ratio was not much lower than it is now in B stars. There have been several abundance analyses of field stars which are probably analogous to horizontal-branch stars in globular clusters. The early A-type star HD 109995 was analysed by Wallerstein and Hunziker (1964) who found a factor 10 metal deficiency, compared with the Sun. Kodaira (1964) obtained a metal deficiency by a factor 13 in the slightly cooler star HD I6I 817. HD26 and HD2o1626, studied by Wallerstein and Greenstein (1964), are somewhat to the right of the vertical part of the globular-cluster giant sequence. They find metal deficiencies by factors of 5 and 30 respectively. In both stars the carbon to iron ratio is five times normal and barium, lanthanum, cerium and neodymium are up by a factor 20. Europium is higher than normal by only a factor z.to 5· The abnormal abundances might be produced by helium burning followed by neutron addition to the iron-peak elements, followed by some mixing to the surface. Searle and Rodgers (1966) have obtained low dispersion spectra of horizontal-branch stars in NGC6397; the metal-to-hydrogen ratio is down roughly by a factor 100 from the Snu.

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Spectroscopic studies of faint stars in the galactic halo have been pursued by Greenstein (1966). He finds He I and He II lines enhanced by factors of 3 to 5 in sdB and sDO stars. He I lines are weakened by a factor 3 in Bp stars. Berger (1963) and Sargent and Searle (1966) have found groups of hot halo stars in which the He I lines are weak and the hydrogen lines are strong compared with those in normal stars of the same colour and Balmer discontinuity. W. L. W. Sargent and L. Searle (1966) have compared Feige n, 36 and 65 stars with T Scorpii and concluded that at least the three halo stars are helium-deficient, a rough estimate being on those objects where the HefH ratio is lower by a factor of 100 than it is in mainsequence stars of Population I. B. Pagel (1965a, b) has derived heavy metals abundance in HDI22563 finding that the ratio FefH is about 250 times weaker than in the Sun; relative to the Sun there is a deficiency of barium, cerium and europium. (l) Miscellaneous Stars

Two main sequence stars of same spectral type and different age, HR2217 Band x Bootis B, were observed by Bardin and Prevot (1964b) and found to have identical chemical composition in their atmospheres. Danziger (1965a) has analysed the starRY Sagittarii which is similar toR Coronae Borealis; the abundance ratio of carbon to hydrogen is 25 and the ratio of carbon to iron is 35 times normal while sodium and lithium abundances are high. l. I. Cepheids In the report of Commission 27 the abundance work on the cepheid f3 Doradus is discussed. Kraft and Abt have studied TV Camelopardalis and found that abundance is normal to within a factor of about 2, and that the cause of the weak lines is a low turbulent velocity.

1.2. Binaries A new discussion on f3 Lyrae from the point of view of the chemical composition is due to Hack and Job (1965). In regard to the subgiant components of Algol systems it is important to mention an investigation that is being carried out by D. S. Hall who has found, using narrow band photometry technique, that there may be an underabundance of CN in the mentioned components. Sargent (1966) has analysed both components of ADS3910, finding that one component is a typical B5 V star and that the companion is deficient in helium by a factor of 100 and in iron and silicon by a factor of IO; the latter star has probably suffered surface activity and may be related to the ,\ Bootis stars. (m) Lithium Abundances in Stellar Atmospheres

Herbig has devoted most of his time to the problem of lithium in F-K stars and its implications. In a first paper (1965) he is concerned with dwarfs in the F5-G8 range; these stars show rather high Li abundances suggesting that convective depletion of Li during contraction cannot have been completed in the mass range concerned and that the variations in Li abundance in F5-G8 dwarfs may be due to a slow process of convective depletion. In a paper on the lithium abundances in F-G and K type subgiants, written in collaboration with R. J. Wolff (1966), it is suggested a mechanism of Li depletion through mass loss which is age-dependent and does not involve continuous Li burning at the base of the convection zone. A programme that Herbig is carrying out at present is that of Li abundance in the later-type component of composite systems, usually G-K + B-A types.

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The problem of the correlation of Li abundance with intensity of H, K emission cores is being dealt with by Herbig by means of an extensive programme of spectrophotometry of the emission cores at 8Afmm, mainly in F-G dwarfs. Wyller is concerned with the problem of lithium in carbon stars on account of possible C13 N 14 line contamination in the calcium and lithium lines used for differential comparisons. The results of his study will be presented at the Joint Discussion in Prague on the lithium problem. Wallerstein et al. (1965) have looked at 23 stars in the Hyades and find lithium to calcium ratios from 3 to 100 times that in the Sun. ForB- V:;;. o·61 the abundance is correlated with temperature, again suggesting destruction by convection into the interior. Further, Wallerstein (1966a) has measured the same ratio in 5 F-type and 6 G-type giants; the F giants show large enhancement of lithium while the G-stars do not. The F component of Capella has 6o times the lithium abundance of the G-star. The change in depth of the convection during the star's evolution is again responsible for the large differences. In order to test Herbig's theory in regard to correlation between a star's lithium content and age, Wallerstein (1966b) has observed visual binaries in which at least one component is of a sufficiently late spectral type (Fo V) that the resonance line of neutral lithium might be present. Six out of nine very young systems have a high lithium content and the upper limits on the lithium content of the other three systems are not in serious disagreement with Herbig's hypothesis. However, several subgiants have a substantial lithium content, in contradiction with Herbig's correlation. As a consequence, Wallerstein suggested a possible mechanism in terms of internal magnetic field that might assist in the preservation of lithium. Some carbon stars have lithium to calcium ratios ten times larger than in the Sun while others show no lithium (Torres-Peimbert et al. 1964). Rodgers and Bell find the abundance of lithium to be more than ten times the solar value in the 35-day cepheid l Carinae. Also an overabundance is found by Danziger and Oke (1966) in VZ Cancri a metal-deficient cluster-type variable. The presence of lithium in this presumably highly evolved star is surprising and suggests that surface reactions may have occurred. Lithium is one of the few cases where atomic lines show isotope shifts large enough to be measured: the shift between Li6 and Li 7 is 7 km s-1 • Herbig (1964) observed 15 F- and G-type stars and found appreciable Li6 in a few of them. A substantial extension of this early work on Li isotope ratios in F-K subgiants is in progress, with some improvements in technique. In two Hyades F-type stars Merchant et al. (1965) found no evidence for Li6• Wallerstein (1965) finds that two metallic-line stars have more Li6 than similar normal stars and suggests the possibility of spallation reactions. In the sunspot spectrum Schmahl and Schroter (1965) found Li 6/Li 7 ~ o·o5. A high dispersion coude programme in progress at Pretoria, being carried out by Feast, aims at determining the Li abundance and the Li6 /Li7 ratio in a variety of southern stars. Among them the bright subgiant f1 H ydri- a member of the p Herculis group- with a general metal deficiency of about 2 or 3, according to Rodgers and Bell ( 1964), a LifCa ratio ten times the solar value and a high Li6 /Li7 ratio (Feast 1967). The Li6/LF ratio appears to be high for lithium-rich subgiants and low for main sequence stars possibly implying lithium production during evolution off the main sequence. Warner (1965c) has discussed a method of deriving lithium abundances from Li 1 equivalent widths. Conti and Danziger have studied further the decrease of lithium with age in field stars and in the Pleiades, and found no difference in the pre-main sequence depletion and that the depletion time scale in G stars seems to be of the order of 109 years. The F stars appear to have a considerable range of initial abundance of Li. 12

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The fact that no beryllium has been found in A or F supergiants led Conti to think that evolution might be from right to left in supergiants. He found no beryllium in the G subgiants 7J Bootis and ' Herculis, making its presence in 8 Eridani even more surprising.

A comparison of the beryllium and lithium abundances in ten F- and G-stars has been made by Merchant (1966) who found a much smaller range of abundances in beryllium than in lithium. M. Bretz (1966) is interested in the presence of lithium inS stars: no lithium was found in the nine bright stars between types M and S that were studied, except perhaps in HD30959. JORGE SAHADE

President of the Commission

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637

APPENDIX I: REPORT ON ABSOLUTE SPECTROPHOTOMETRY

(Prepared by J. B. Oke) Since the last IAU meeting in Hamburg, little fundamental absolute calibration work has been carried out. Material discussed at that time has now appeared in print. Willstrop (r965) has published energy distributions of 215 stars of types 0 5 to M4 with measures made over successive so-angstrom bands from AfOOO to ,\6900. He also made comparisons with standard lamps. A sequence of early-type stars near the celestial equator and suitable for absolute spectrophotometric standards has been measured by Oke (1964). All stars have been observed from -'3390 to -'5900 and some out as far as .\108oo. It now appears likely that in this list all the absolute spectrophotometric magnitudes below the Balmer jump should be made fainter by approximately o·o6 magnitude on the basis of the best absolute data now available for oc Lyrae. Aller, Faulkner, and Norton (I964, 1966) have published absolute fluxes for more than 20 southern stars. They have been tied to the standards of Oke (I964). The remaining papers on absolute spectrophotometry have been primarily for the purpose of determining fundamental data about stars, i.e. log Te and log g. These are used to determine accurately the locations of stars in the Hertzsprung-Russell diagram and for obtaining the parameters needed in chemical abundance analyses. Glushneva ( I964) has obtained absolute energy distributions of If B 9 to A 7 and seven earliertype stars from .\3ooo to -'4700, using photographic slitless techniques. More recently four additional early-type stars have been studied (Glushneva, I966). Oke (I965) in a review article discussed some of the observational problems associated with absolute spectrophotometry and gave energy distributions for a number of stars. Baschek and Oke (I965) have measured II Am, Ap, and normal A stars from ,\ 3400 to ,\I o 8oo. Measures have been corrected for absorption lines and a temperature scale is given. Oke and Conti (I966) obtained continuum energy distributions from -'3400 to AI08oo for 24 Hyades stars of spectral types A3 to Ko. The relation of B - V to log Te is given. Whiteoak {I966) obtained absolute fluxes from -'3448 to ,\ ro 500 for 38 early-type stars to study the interstellar extinction law. Oke, Greenstein and Gunn (I966) obtained and discussed energy distributions of a number of suspected field horizontal branch stars. Karetnikov and Medvedev {I966) have described a new spectrometer and published energy distributions from .\38oo to .\58oo of oc Andromedae, f3 Arietis and oc Cygni. Baschek, Oke and Searle (unpublished) have obtained absolute energy distributions from ,\ 3400 to ,\I o 8oo of all known ,\ Bootis stars. Aller and Faulkner (r964) obtained spectrophotometric data for the WR star y Velorum. Kuhi (r966) obtained absolute fluxes from A-3200 to ,\II ooo of many nothern WR stars. He finds high colour temperatures in the blue and violet and lower ones in the visual and red. Kupo (r965) obtained gradients and Balmer jumps around the cycle of f3 CMa. Oke (I966) has obtained similar data for the very metal-deficient RR Lyrae star X Arietis. Rodgers and Searle at Mt Stromlo have scanned TJ Carinae and discovered a red continuum similar to that of the nucleus of the Seyfert galazy NGC4r5r and to the Crab nebula. Comparison of absolute Hoc fluxes and radio-thermal emission in the surrounding H II region leads to a value of AvfEB-V of 6. In the infrared, Woolf, Schwarzschild and Rose (r964) using Stratoscope II obtained scans from o·8 to 311- of 6 K- and M-type stars. These were all compared directly with the Ar star oc Canis Majoris. Low and Johnson (r964) have extended their broad-band photometry out to IOJl-. They now have sufficient infrared points to represent at least approximately a large part of the spectral energy distribution of cool stars. Wildey and Murray (r964) have also made measurements of 25 stars at IOJl-. Johnson (r965) has obtained broad-band colours out to 3·511of 43 K- and M-type stars. Mendoza and Johnson (r965) obtained colours out to IOJl- for many carbon stars.

638

COMMISSION 29 BIBLIOGRAPHY

1964, Astrophys. J., 140, 167. Aller, L. H., Faulkner, D. J. 1964, Astrophys. J., 140, 1609. Aller, L. H., Faulkner, D. J., Norton, R. H. 1966, Astrophys. J., 144, 1073. Aller, L. H., Faulkner, D. J., Norton, R. H. 1965, Astrophys. J., 141, 1404. Baschek, B., Oke, J. B. 1964, Astr. Zu., 41, 212. Glushneva, I. N. 1966, Astr. Zu., 43, So. Glushneva, I. N. 1965, Astrophys. J., 141, 170. Johnson, H. L. 1966, Astr. Zu., 43, 873. Karetnikov, V. G., Medvedev, Y. A. 1966, Astrophys. J., 143, 753· Kuhi, L. V. 1965, Astr. Zu., 43, 358. Kupo, I. D. 1964, Astrophys. J., 139, II30. Low, F. J., Johnson, H. L. 1965, Astrophys. J., 141, 161. Mendoza, E. E., Johnson, H. L. 1964, Astrophys. J., 140, 689. Oke, J. B. 1965, A. Rev. Astr. Astrophys., 3, 23. Oke, J. B. 1966, Astrophys. J., 145, 468. Oke, J, B. 1966, Astrophys. J., 143, 134. Oke, J. B., Conti, P. S. 1966, Stellar Evolution, Ed. R. F. Stein and A. G. W. Oke, J. B., Greenstein, J. L., Gunn, J, Cameron, Plenum Press, New York, p. 399· 1966, Astrophys. J., 144, 305. Whiteoak, J. B. 1964, Astrophys. J., 139, 435· Wildey, R. L., Murray, B. C. 1965, Mem. R. astr. Soc., 69, 83. Willstrop, R. V. 1964, Astrophys. J., 140, 833. Woolf, N.J., Schwarzschild, M., Rose, W. K. After the report by Dr Oke was written the following additional information was received: ZileviCiute and StraiZys (1965) have studied the energy distribution in the continuous spectrum of y Cassiopeiae during 1964-65. The energy distribution in the continuous spectrum of RW Aurigae has been studied by Mirzoyan and Kazarian (1965) and by Kharadze and Bartaya (1965). A more or less intense UV-continuous emission is permanently present in the stellar radiation and the energy distribution changes conspicuously with light variation. At Alma-Ata the work of establishing spectrophotometric standards is in progress. Karjagina and Haritonov (1964) have made absolute measurements of flux at different wavelengths for a number of stars and published results for 34 stars. Haritonov (1964, 1966a) has published absolute measurements for 17 field stars and for 14 Pleiades stars (1966b). Haritonov and Neljubin (1966) have made absolute measurements of the fundamental star a Lyrae, calibrating with the integral flux from the centre of the solar disk. Noskova (1965) has found that the energy distribution of the nuclei of the planetary nebulae NGC4o, 3242, 6210, 6543, 6572, 7009, 7662, IC2149, 4593 and BD + 30°3639 is similar to that of a black body. Glagolevsky (1966) has studied the energy distribution of magnetic and Ap stars and found that on the average the spectrophotometric gradients and the Balmer discontinuities differed from those of normal A stars. At Alma-Ata, Kozlova and Glagolevsky (1966) have investigated the energy distributions in the continuous spectra of 40 Ap and Am stars within the range U32oo-soooA and concluded that these stars have the same anomaly in their continuum and that such an anomaly might be connected with the same anomaly in the structure of the atmosphere. Energy distributions have been measured by Aller in the .U 330o-58oo range for the following stars: 2 Coronae Borealis, ' Virginis, HR4072, 15 Cancri, 53 Tauri, "' Virginis, HD 144206, 112 Herculis, HR8349, T Capricorni, rp Herculis, ' Herculis, HR8348, 1r1 Bootis.

SPECTRES STELLAIRES

639

G. Cayrel and A.M. Fringant (I964) have given the results of a spectrophotometric study of two metal deficient stars, HD221 I70 and HD I22 563, which show a difference in blue gradients that suggests a local difference of the absorption coefficient. BIBLIOGRAPHY

Cayrel, G., Fringant, A.M. 1964, C. r. Acad. Sci. Paris, 258, 3195 (Pub!. Obs. Hte.-Provence, 7, no. 34). Glagolevsky, J. V. 1966, Astr. Zu., 43, 7J. Haritonov, A. V. 1964, lzv. Akad. Nauk Kazakh. SSR. Ser. fiz. mat. Nauk Astrofiz., 3, 28. Haritonov, A. V. 1966a, Trudy astrofiz. Inst. Akad. Nauk Kazakh. SSR, 7, 9· Haritonov, A. V. 1966b, Astr. Cirk, no. 43, in press. 1966, Trudy astrofiz. Inst. Akad. Nauk Kazakh. SSR, 8, Haritonov, A. V., Neljubin, N. T. in press. 1964, Izv. Akad. Nauk Kazakh. SSR. Ser. fiz. mat., 3, 10. Karjagina, Z. V., Haritonov, A. V. Kharadze, E. K., Bartaya, R. A. 1965, Astrofizika, I, 405. Kozlova, K. 1., Glagolevsky, J. V. 1966, lzv. Inst. Akad. Nauk Kazakh. SSR, in press. 1965, Astrofizika, I, 213. Mirzoyan, L. V., Kazarian, E. S. Noskova, R. I. 1965, Astr. Zu., 42, 1038. ZileviCiute, Z., Straizys, V. 1965, Vilnius Univ. Bull., no. 15, p. 49. APPENDIX 2: REPORT OF THE COMMITTEE ON LINE INTENSITY STANDARDS

(Prepared by G. Cayrel de Strobel, Chairman of the Committee) During the XIIth IAU General Assembly (Hamburg I964), K. 0. Wright and G. Cayrel de Strobel prepared a list of 20 astronomers who could possibly collaborate in the working group on Line Intensity Standards of Commission 29. These astronomers have been chosen either because of their previous interest in this problem, or because they have high dispersion equipment at their disposal. To these astronomers, G. Cayrel de Strobel sent a circular letter on 3 I March I 96 5 explaining the ever present difficulties of systematic discordances in equivalent widths obtained from different spectrographs. G. Cayrel de Strobel suggested in her circular the observation of five standard stars with a dispersion equal to or better than 12Ajmm on II-aO, II-aD, and II-aF plates. These stars are: y Pegasi B2, 5 IV, 68 Tauri A2 V, I5 Vulpeculae ML, "' Canis Minoris F5 IV and E Virginis G9 III. For calibration, a double calibration has been suggested: one with the local system and one with the Kienle step-filter, which could be sent from one observatory to another. A list of reasonable unblended lines was enclosed in the circular in order to define not only standard stars, but also preferred standard lines to be used for comparison. The following remarks are based upon the replies to the circular, made either in writing or in person. Five astronomers did not reply at all. H. A. Abt (Kitt Peak Observatory) answered only recently that he agreed to collaborate but has not yet begun to observe any of the requested stars. A. A. Asaad (Helwan Observatory, Cairo) has used the 74-inch coude spectrograph of the Helwan Observatory to obtain spectra of the five programme stars. W. Buscombe (Mt Stromlo Observatory) did not answer, but L. Searle promised to observe some of the programme stars with a dispersion of z·8 and 6·7 Ajmm with the 74-inch coude spectrograph of Mt Stromlo Observatory. By the way, L. Searle found that the line-intensity programme is too heavy. He believes that three stars would be enough, and he suggested: y Pegasi B2·5 V, "' Canis Minoris F5 IV, and E Virginis G9 III. He thinks also that the number of standard lines for each emulsion should be reduced and called attention to the fact that the circular did not mention the number of plates for each emulsion. He suggested two plates.

COMMISSION 29

640

R. Cayrel and G. Cayrel de Strobel (Haute-Provence Observatory) sent a graduate student, Miss C. Moreau, to the Haute-Provence Observatory to work on the programme. C. Moreau has observed three stars: 68 Tauri, IS Vulpeculae and ex Canis Minoris. The results obtained are contained in her 'diplome d'etudes superieures' (I966). This work will appear in the Journal des Observateurs and an abstract is given here: 68 Tauri A2 V The relation between the equivalent widths of 68 Tauri obtained from spectra taken at Victoria (Wright et al., I964) and the equivalent widths of 68 Tauri from spectra taken at the Observatory of Haute-Provence (OHP) is given by the formula:

W (Victoria ) _ 0 .8 W ( OHP ) 9 9·7A/mm 3·4A/mm -

+

4

The comparison between Lick equivalent widths of 68 Tauri taken from Conti et al. (I965) and OHP ones gives ( OHP ) Lick ) W ( IO·sAfmm = I"JI W 9"7A/mm - 45 I

) Victoria ( W 7• 5 A/mm at Hy (

5 Vulpeculae M L =

( OHP ) 0"89 W 9·7 A/mm

+9 (

Palomar)

Victoria

OHP )

W 2·8 and 3·4A/mm' 4·sA/mm = o· 9o W 9·7A/mm W(

+2

( OHP ) Mt Wilson ) 2·8 and 4·sA/mm = I·o4 W 9·7A/mm - 18

In the two first relations, the equivalent widths of Victoria and Palomar have been taken from K. 0. Wright et al. (1964) the last one from G. R. Miczaika et al. (I956). ex Canis Minoris

Fs IV

For ex Canis Minoris, C. Moreau compared equivalent widths obtained from 3·2A/mm OHP spectra with those obtained from 9·7 A/mm OHP spectra. She obtained:

W ( OHP )

( OHP ) J·zAfmm = 0"95 W 9"7 Afmm

+5

Then she compared the following sets of equivalent widths ) Victoria ( W 7·sA/mm at Hy

W

=

( OHP ) 1. 17 W 9·7 A/mm

+6

( OHP ) ( from Hiltner and Williams Atlas) = I·o4 W 9·7A/mm 2·8Afmm at Hy

W(

McDonald ) 2·8Afmm at Hy

= ~" 18 W

(

OHP ) 9·7A/mm

+

I7

+ 46

641

SPECTRES STELLAIRES W ( OHP ) ( Bergedorf ) 9·7 Afmm W 8Afmm at Hy = o· 9o

w( 12A/mm Asiago at

Hy

) = I·28

+4

6

w(9·7A/mm OHP ) + 22

The equivalent widths from Hiltner and Williams, McDonald, Bergedorf and Asiago have been taken from Hiltner and Williams (I946 Photometric Atlas of Stellar Spectra), Greenstein (I948), Wellman (I955) and Taffara (I953)· The spectrophotometric calibration has been checked by C. Moreau with the help of Kienle's step-filter. No significant difference was found with the current calibration obtained at the OHP. In the case of oc Canis Minoris it is likely that the differences found in equivalent width measurements do not come from photographic effects (Edmonds, I965; Moreau, I966) but from the rather subjective way in which the continuum is located and the wings of the lines are drawn. In this connection the following remark can be made: C. Moreau measured a certain number of lines of oc Canis Minoris on the Hiltner and Williams atlas. Greenstein independently did the same. The two sets of measurements compared with the OHP measurements are quite different. This result does not involve different instruments but only different personal judgements. By the way, Greenstein and Hiltner (I949) found that the equivalent widths obtained from the Hiltner and Williams atlas should be reduced by about 8%. G. Cayrel de Strobel has compared equivalent widths from nine spectra of ~: Virginis taken at Mt Wilson Observatory (Cayrel, G., Cayrel, R., I963) with those from I I spectra taken at the Observatory of Haute-Provence (Cayrel de Strobel, I966). She found: ~:

Virginis G9 III

Mt Wilson ) ( OHP ) ( W I·o and 2·8A/mm = o· 9o W 9·7 and I2·4A/mm

+8

C. and A. Cowley (McDonald Observatory) have agreed to observe some standard stars with the McDonald 82-inch coude spectrograph. In the meantime, equivalent widths of oc Canis Minoris measured chiefly on 4·8 Afmm McDonald coude spectra have been published by F. N. Edmonds (I965). The comparison between McDonald equivalent widths of oc Canis Minoris spectra, and the means of equivalent widths found by K. 0. Wright for oc Canis Minoris from Victoria and Mt Wilson spectra, gives: W

( McDonald) 4·8A/mm

=

Mt Wilson) ( Victoria o· 97 W 4·6 and 2·2A/mm' 2·9Ajmm

+5

and the comparison between McDonald and OHP gives

W (McDonald) _ I·o 6 W ( OHP ) 4·8Ajmm 9·7 and I2·4Ajmm

+ II

This last result relies unfortunately on a very scarce number of lines (seven lines). V. Fujita (Tokyo Observatory) wants to collaborate and is eager to receive the step filter to check Tokyo's calibration system. L. Gratton (Laboratorio de Astrofisica di Frascati-Roma) has not yet any high dispersion equipment at his disposal, but he comments on some of his previous works (Gratton I953)· The equivalent widths of the K2 III p Star oc Bootis obtained from McDonald spectra do agree with those of Victoria, but do not agree with those obtained from the Hiltner and Williams atlas. Gratton does not believe in continuous calibration systems but prefers step filter. For high dispersion analysis on G and K stars, he does not trust dispersion less than 10Ajmm.

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COMMISSION 29

J. L. Greenstein (Mt Palomar and Mt Wilson Observatories) transmitted the circular toP. S. Conti, who sent to G. Cayrel de Strobel a few interesting comments but did not say anything about a collaboration on this programme. Conti (1965) found that the equivalent widths of 45 Tauri dF4 from IoAjmm Mt Wilson spectra were systematically stronger by 15% than those from 10Ajmm Lick spectra. Wallerstein and Conti (1964) found also that the equivalent widths of the Ko III giant y Tauri from 15AJmm Mt Wilson spectra were 5% stronger than the Mt Palomar ones (dispersion 13·sA/mm) and 25% stronger than the Lick ones (dispersion 16Ajmm). Helfer and Wallerstein (1964) have compared equivalent widths from 6·o and 6·7 Ajmm spectra of E Virginis with those obtained by the Cayrels (1963) on z·8Ajmm spectra, and they did not find any significant differences. G. Herbig (Lick Observatory) agreed to collaborate, but on a less heavy programme. He would like to observe one or two stars out of five and to measure a few lines out of the proposed one. Until now only 68 Tauri among the five standard stars has been observed (Conti et al., 1965), and some of its equivalent widths have been measured on Lick Io·sAJmm spectra. The comparison between these equivalent widths and those of the Observatory of Haute-Provence has already been quoted. J. Houtgast (Utrecht Observatory) is always interested in the problem of line intensity standards, but thinks that at Utrecht, he cannot help with it at the present. B. E. J. Pagel (Herstmonceux Observatory) will collaborate on this programme, but only with blue plates, and will take IoAjmm spectra of the standard stars. The dispersion in the red and yellow region is below the requested limit. In his letter Pagel also suggests that spectra be taken of integrated sunlight from sky, Moon or minor planets with the equipment of each of the collaborating observatories. The different set of equivalent widths should then be compared with the excellent photoelectric measurements of MacMath (see for example Muller and Mutschlecner, 1964) which can be converted into values for integrated sunlight by a very simple numerical quadrature. This procedure will tell what is really wrong with everybody's equivalent widths, rather than merely how much they disagree with each other.

J. Sahade (La Plata Observatory) has not yet any high dispersion equipment at his disposal in Argentina but is willing to collaborate securing programme stars spectra whenever he would have observing runs at Mt Wilson. This would be indeed very welcome. A. D. Thackeray (Radcliffe Observatory) will try to collaborate and take some 6·8Ajmm spectra in the blue region of a few programme stars, but he does not have facilities for measuring the lines equivalent widths from the plates. G. Cayrel will try to find a student to do this work in Paris. S. Taffara (Asiago Observatory) found a young astronomer, P. L. Bernacca, who is willing to observe the programme stars and measure the equivalent widths of the requested lines. The calibration system of Asiago has already been checked with Kienle's step filter a few years ago. K. 0. Wright (Victoria Observatory) has done the most accurate and extended work on line intensity standards which has ever been done (Wright et al., 1964). Equivalent widths measured on Victoria, Mt Wilson and Mt Palomar spectra, of twelve main sequence stars Bo to G5 have been compared. The spectral range has been 3900 to 45ooA, and the number of lines measured passed soo in the F type stars. The results are already contained in Wright et al. (1964) and in the Transactions of the 12th IAU General Assembly. In spite of his already impressive contribution, Wright will collaborate on this programme and get some spectra of the requested stars with a better resolution than the resolution of the spectra he used in his former study. Wright found also that the combination of a II-aD plate from 48oo to 6zooA with a II-aE plate from 6zoo to 66ooA gives approximately the right density all along the plates whereas the II-aF is a little too weak.

SPECTRES STELLAIRES

643

Regarding Pagel's suggestion of using the solar spectrum as a standard, Wright suggests the use of planetary or asteroid spectra. He fears that the spectrum of the daytime sky light may be affected by scattered light. Some Conclusions on Line Intensity Standards

There is a statement one can make: until now we have not been able to give any easy correlations between the values of equivalent widths obtained with one instrument and the values obtained with another. K. 0. Wright gave us (Taffara, 1962) the correlations between Victoria, Mt Wilson and Mt Palomar, but every time we reduce new material we have to check: (1) if, between the equivalent widths coming from different spectra taken at the same instrument, there are not big systematic differences; (2) if the mean of equivalent widths of the new material has the same value as the mean formerly found for this instrument. From the paper by Wright et al. (1964) we see that the equivalent widths obtained from photoelectric scans are in good agreement with those obtained by photographic means. They tend to be slightly larger than those obtained by Wright and Greenstein at Mt Wilson, but almost coincide with the photographic means of equivalent widths measured on high dispersion spectra. In the near future it will be necessary to pass slowly to the technique of observing one or two standard stars and of comparing the equivalent widths obtained by photographic means with those obtained from spectrophotoelectric scans. Therefore we suggest that we ask the observatories which already have spectrophotoelectric equipment to scan the standard stars we shall propose. Once we obtain equivalent widths from photoelectric scans of different instruments, we have to see if they agree with each other. This set of equivalent widths will then be compared with the photographic measurements of equivalent widths obtained from high dispersion spectra with different instruments. The programme has been regarded as too heavy by almost every co-worker. Therefore, it would be perhaps more practical to reduce the programme to one star and the solar spectrum for which excellent photoelectric measurements do already exist. BIBLIOGRAPHY

Cayrel de Strobel, G. 1966, Ann. Astrophys., 29, 413. Cayrel, G., Cayrel, R. 1963, Astrophys. J., 137, 431. Conti, P. S. 1965, Astrophys. J. Suppl., II, 47· Conti, P. S., Wallerstein, G., Wing, R. F. 1965, Astrophys. J., 142, 999· Edmonds, F. N. 1965, Astrophys. J., 142, 278. Gratton, L. 1953, Me'm. Soc. R. Liege, 14, 419. Greenstein, J. L. 1948, Astrophys. J., 107, 151. Greenstein, J. L., Hiltner, W. A. 1949, Astrophys. J., 109, 265. Helfer, H. L., Wallerstein, G. 1964, Astrophys. J. Suppl., 9, 8z. Miczaika, G. R., Franklin, F. A., Deutsch, A. J., Greenstein, J. L. 1956, Astrophys. J., 124, 134·

Moreau, C. 1966, Diplome d'Etudes Superieures. Muller, E. A., Mutschlecner, J.P. 1964, Astrophys. J. Suppl., 9, I. Taffara, S. 1953, Contr. Oss. astrofis. Univ. Padova, no. 32. Taffara, S. 1962, Contr. Oss. astrofis. Univ. Padova, no. 126. Wallerstein, G., Conti, P. 1964, Astrophys. J., 140, 858. Wellman, P. 1955, Z. Astrophys., 36, 194. Wright, K. 0., Lee, E. K., Jacobson, I. V., Greenstein, J. L. 1964, Publ. Dom. Astrophys. Obs., Victoria, 12, 173.

30. COMMISSION DES VITESSES RADIALES PRESIDENT: Dr R. M. Petrie t, Dominion Astrophysicist, Dominion Astrophysical Observatory, Victoria, B.C., Canada. VICE-PRESIDENT, PRESIDENT PAR INTERIM: Dr D. S. Evans, Royal Observatory, Observatory, Cape Province, South Mrica. SECRETAIRE: Dr W. Buscombe, Mount Stromlo Observatory, Canberra, A.C.T., Australia. CoMITE n'ORGANISATION: F. K. Edmondson, Ch. Fehrenbach, J. F. Heard, A. D. Thackeray. MEMBRES: Abt, Batten, Bouigue, Boulon, Duflot, Gollnow, Gratton, Kraft, Northcott, Pagel, Preston, Sahade, Underhill, Wayman. The Commission suffered a severe loss by the death on 8 April, 1966 of its President, Robert Methvcn Petrie, a few weeks before his 6oth birthday. Well known to astronomers throughout the world, Petrie was, at the time of his death, Dominion Astronomer of Canada and Director of the Dominion Astrophysical Observatory at Victoria, British Columbia. He was a Vice-President of the IAU from 1958 until 1964. He served as a member of Commission 30 from 1950 onwards, being its Vice-President from 1961 to 1964, when he became President. From 1950 to 1955 he was President of the Sub-Commission on Standard Wavelengths. His astrophysical contributions were numerous and diverse. Within the field of our Commission his influence was of capital importance. His work on standard wavelengths and on methods of measurement of spectra has been of fundamental importance to our knowledge of the velocities of early-type stars. His analyses of the motions of B-stars, and of the equivalent widths of the Balmer lines in their spectra have been corner stones in the edifice of modern ideas concerning galactic structure. IAU SYMPOSIUM NO. 30 At the time of his death, Petrie was engaged in planning IAU Symposium No. 30, to be held in Toronto from 20 June to 24 June 1966, on the topic, 'Determination of Radial Velocities and their Applications'. His sudden death brought home to the surviving members of the organizing committee, the full realization of their dependence on him. Even so, the ground work which he had laid had been carried out with such foresight and care, that the Symposium took place successfully, very much as he had planned it. The meeting, which was thus transformed into a kind of memorial to our late President, could not have taken place but for the devoted efforts of the organizing committee, especially the Canadian members, and, more particularly, Professors Heard and MacRae of Toronto. The Symposium took place on the Campus of the University of Toronto, by courtesy of the University authorities, under the presidency of the acting President of the Commission. About 6o astronomers attended. Since the printed report (1), dedicated to R. M. Petrie, is likely to be published before the Prague General Assembly, no detailed account is needed here. However, because certain contributions were of outstanding interest, while others are not mentioned elsewhere in this report, a partial list of topics discussed is included. Among new techniques presented, especially notable was the photo-electric method of Griffin. Mrs Rubin and her co-authors represented the growing body of observers using image tubes, particularly for very faint objects. De Vaucouleurs demonstrated velocity measures of galaxies by a scanning technique and by a photoelectric method. Oscilloscope plate-measuring device were described by Gollnow and by Andrews and their inherent errors discussed by Scarfe. 645

646

COMMISSION 30

A paper by the late R. M. Petrie and J. M. Fletcher demonstrated techniques for attaining extremely high accuracy with a coude spectrograph. Weaver described his definitive reduction of Trumpler's velocities of stars in clusters. This is likely to become a standard reference for classical photographic methods of radial velocity measurement. Abt reported the near completion of a catalogue project including a plate-by-plate measurement catalogue of the Mount Wilson material. The Marseilles-Haute-Provence group, led by Fehrenbach, gave a general conspectus of their objective prism work. Bertiau described a very comprehensive Fortran programme for the determination of elements of spectroscopic binary orbits. Dommanget reported the appearance of his catalogue of visual binaries worthy of spectroscopic observation. There was a considerable interest in the evolutionary significance of the properties of binary stars and several speakers discussed their statistics (e.g. Batten, Blaauw, Bouigue). In a subsequent brief report to the Executive Committee regret was expressed that there had been no opportunity to welcome to the Symposium colleagues from the countries of eastern Europe and Asia, and it was hoped that in future astronomers from these areas would join in the activities of our Commission. It is therefore very gratifying to receive a report from the U.S.S.R. which is included below. REPORTS FROM OBSERVATORIES

The next part of the report summarizes, as has become customary, the written reports received from various observatories.

Allegheny Observatory Beardsley reports: The radial velocity programme continues essentially without change since being reinstituted in 1958. It consists of all stars listed as SB, without orbit in the Wilson Radial Velocity Catalogue, brighter than magnitude 7·0, earlier than Go, and north of -20° declination. A few additional stars fainter than 7·0 or later than Go have been placed on the programme from time to time. The programme is supplemented by those stars north of -20° listed in the new Bright Star Catalogue as having no radial velocity. A number of Be stars and a group of stars designated as 'Astrometric-Spectroscopic Binaries' are being observed as well. Instrumentation consists of the Keeler 31-inch (79 em) reflector and Mellon one-prism spectrograph giving a dispersion of 4oAjmm at Hy. Standard velocity stars are observed at every session in an effort to tie the programme directly to the standard velocity system. Measures are made on a null-projection machine similar to that used at Victoria. A Grant machine will be installed in 1966. With National Science Foundation support the output of radial velocities from Allegheny should be much increased in 1967. To date over 28oo plates have been taken. In the next few years an extensive analysis of the quality of these radial velocities will be undertaken. It is expected that nearly 3000 radial velocities from the period 1905-17 will be published in 1967.

Cambridge Observatories Griffin reports that he has developed the Cambridge technique of narrow-band stellar photometry with a slit spectrometer to measure radial velocities photoelectrically (2). A diaphragm containing 234 apertures whose positions correspond to those of strong lines in the

647

VITESSES RADIALES

blue region (.\.\4370-483oA) in the spectrum of Arcturus, is matched against the spectra of other late type stars and its position then determines the relative Doppler shift. Using the Cambridge 92 em-reflector, stars of mv = 9 are measured to about 2 km s-1 standard error at the rate of 6 to 8 stars per hour. All stars later than about can be measured using the same diaphragm. Observations of fifth magnitude stars of which the velocities have been determined photographically confirm the freedom of the method from detectable systematic errors, and show a standard deviation of I km s-1 per observation at this magnitude. Some hundreds of velocities, mainly in the + IS 0 selected areas, have been measured with the new equipment. A series of observations of the spectroscopic binary, 73 Leo, has also been made (3).

Gs

Mount Strom/a Observatory, Canberra Observations of B-stars in four selected fields along the Southern Milky Way (at longitudes I7°, 24S 0 , 3I2° and 328°) which had been started by B. J. Bok, Gollnow and Mowat, are now almost completed. These were made with the grating spectrograph at the Newtonian focus of the 74-inch (188 em) reflector. Preliminary results for the stars at 24S 0 and 328° (Puppis and Norma) have been given by Mowat at the Mount Stromlo Symposium (4) and at IAU Symposium No. 30 (1). In both cases the distances derived for these groups of stars from their radial velocities are in very good agreement with those derived from H~ photometry. The group in Norma appears to belong to the nearer Sagittarius arm rather than to the more distant NormaScutum arm. The observations of selected nebulosities and stars in the Large and Small Magellanic Clouds made with the same instrument (Bok, Gollnow and Mowat) are also practically completed, and some of the results for the Small Cloud have been published in cooperation with Hindman of the Radiophysics Laboratory, Sydney, who made radio measurements in H I (5). The same equipment has been used by Westerlund, Stokes and Lewis to investigate radial velocities of southern galaxies, and of some supernova remnants seen as emission nebulae in the Milky Way and Magellanic Clouds. The 32-inch (81 em) camera of the Mount Stromlo coude spectrograph has been used by Dunham and by Buscombe for studies of velocities of interstellar clouds from measures of the Ca II and Na I absorption lines. Bessell has studied the velocity variations of several dwarf cepheids, mainly with the 10-inch (2S em) R.E.O.S.C., camera. The 2-prism Zeiss spectrograph, transferred to the Cassegrain focus of the so-inch (I27 em) reflector, has been used by Buscombe to complete a study of the cluster, Messier 7, and to obtain velocity measures of B8 stars (in cooperation with Heard) and supergiants (many of which had been recognized photometrically by Walraven). Webster has completed a study of planetary nebulae in the Galaxy and Magellanic Clouds, and Roslund has made observations of B stars in the III Sgr association. A new grating spectrograph, designed by Meinel, has been brought into use on the 40-inch (102 em) reflector at Siding Spring for studies of long-period variables by Buscombe, and of galactic B-stars by Lynga, and of members of the III Pup association by Westerlund. A more elaborate model of the impersonal setting device with greatly improved electronics has been put into use (Gollnow, Rudge and Thomas, (x)). References (6) to (x6) cover recent publications embodying radial velocity measures which have not previously been noted in these reports. They include velocities for about field stars.

sso

Royal Observatory, Cape of Good Hope Two more papers in the series of Fundamental Data for Southern Stars, (Nos. s and 6) (17), (18), have been published. Material for a further list is available on file. A considerable K2

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number of new sub-dwarfs is included in these lists. Attention has been paid to the rapid handling of data for spectroscopic binaries. Orbital elements for nine stars of which HD 2070, 15064,123 515,155099,159656, I83007, 194I84,2oo334are single-lined and HD 188164 doublelined, are in press (I9). During his visit to the University of Texas, Evans collaborated with Andrew T. Young in devising an analogue method for rapid determination of the periods of recurrent phenomena such as velocity variation in spectroscopic binaries (20). In addition, computer programmes were written by E. Barker and D. Wells, on the one hand for the iterative determination of orbital elements, on the other, as a development of Lafler and Kinman's method, (2I) for the determination of periodic times. The Cape-Radcliffe programmes have been occupied recently to a large extent by further work on a selected list of RR Lyrae stars, for which both photometric and spectroscopic observations are planned. For the list of about 6o stars some 260 spectra have so far been obtained. In recent months D. H. P. Jones, Clube and Menzies have been concerned in this work. A short list of extragalactic velocities based on spectra obtained with the new Newtonian spectrograph at the Radcliffe Observatory was published by Evans and Malin (22). Some further spectra have recently been obtained by D. H. P. Jones. A note on the cepheid HR 5527 (misprinted as 5227), previously thought to be a double star, HD I3070I/2, has been published by Evans (23). Owing to the interruption consequent on his visit to the U.S.A., Evans has not yet completed his new analysis of p Velorum but this should be finished shortly (I). For the same reason the revision of the Mount Wilson Radial Velocity Catalogue has lagged, though Miss Y. Z. R. Thomas has continued work on this. The card catalogue contains some 9500 cards, each referring to a star, about equally divided between stars which have been previously observed, and new stars. It is hoped to report definitive progress on this project at the Prague General Assembly (I). D. H. P. Jones (24) has extended the error investigation of Wayman (25) to the two Herstmonceux spectrographs and finds that the additional error element to be applied in passing from formal probable error to real standard error has the same value as for the Pretoria cameras. Expressed in terms of microns on the plate it has the same value for all the cameras of all three spectrographs. D. H. P. Jones and H. C. Lagerweij (26) have made a spectroscopic and photometric study of the S Scuti variable, I Monocerotis (HD40535). David Dunlap Observatory, Toronto Since 1964 the Hilger Prism spectrograph at the Cassegrain focus of the 74-inch (188 em) telescope has been replaced by an all-reflection grating spectrograph which has dispersions of 10Ajmm and 4oAjmm. Crampton and others (I) have found that the 4oAjmm grating system is faster than the 66Afmm prism system and comparable in accuracy for the determination of radial velocities with the 33 Ajmm prism system. A Grant oscilloscopic comparator is now in use for measuring spectrograms, and programmes have been devised for the reduction of measurements by electronic computer. Heard (27) has published the radial velocities of 55 Kapteyn Area fundamental stars in high galactic latitude. Heard and Petrie (I) have investigated the radial velocities and other criteria of cluster membership for 77 stars in the field of the a Persei cluster. Spectroscopic binaries were found to be rare in this cluster.

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Crampton has completed the observations for a programme of radial velocities of 6o Be stars, the purpose of the investigation being a kinematic study with the help of distances derived from Schmidt-Kaler's absolute magnitude calibration. Hube has nearly completed a radial velocity programme of 250 B8-Bg stars of the Bright Star Catalogue north of declination -26° and as yet unobserved for radial velocity, and he proposes to extend this study to more southerly B8-Bg stars at the Radcliffe Observatory. He will attempt to correlate his velocity data with distances, age grouping, and rotational velocities.

Dunsink Observatory Radial velocities of 3 r 5 southern stars south of declination - 20° of photographic magnitude about 8·5, evenly distributed over the sky, with spectral types in the Henry Draper Catalogue from F5 to Mb have been determined on the system of the General Catalogue of Radial Velocities. The spectra were obtained in 1958-6o at the Radcliffe Observatory, Pretoria as a programme undertaken on behalf of the Royal Greenwich Observatory. Photoelectric measures of Uc, B and V for these stars have been made at the Royal Cape Observatory. A list of the data, including MK spectral types derived visually has been communicated to Evans for inclusion in the revision of the General Radial Velocity Catalogue (28). Densitometer tracings of the spectra are now being made at Dunsink for spectral classification purposes.

Royal Greenwich Observatory, Herstmonceux Woolley and Harding (29) have published radial velocities of g6 stars derived from 241 spectra obtained with the coude spectrographs at Mount Wilson and Palomar, and Radcliffe Observatories. Twelve double stars and nine stars in the Hyades are included. The possibility of a systematic difference between the measured velocities of giants and dwarfs in the same cluster is considered. Harding has published radial velocities of bright members of the globular cluster w Centauri (30). Woolley and Aly (31) have published radial velocities of r8 RR Lyrae stars, for which, in most cases, the velocity curves are obtained. At Herstmonceux the grating spectrograph with dispersions of 40 and 8oAjmm at the Cassegrain focus of the Yapp 36-inch reflector is being used for the determination of radial velocities of a list of spectroscopic binaries brighter than 7"5 mpg• for which no orbital elements have previously been determined. Radial velocities of 633 stars of HD spectral types Bg-A5, brighter than mv = 6·3 and north of the equator, have been determined, using the 1 prism spectrograph. Estimates of spectral type and of I v sin i I have also been made, and the results are in press (D. H. P. Jones, Palmer, Walker and Wallis (32)). A coude spectrograph with a dispersion of roAjmm in the second order in the blue, attached to the 30-inch (76 em) reflector, has been brought into use. A programme of measurements of radial velocities of IAU standard stars has been undertaken to test the stability of the instrument, and the results, accompanied by a description of the instrument, are in press (Harding, Palmer and Pope (33)). In 1965, D. H. P. Jones observed five stars intensively at 8oAjmm with the Yapp reflector, in a search for short-period velocity variation. Only one star, HD 107904, was found certainly to show variations. It has since been confirmed as a a Scuti variable by Wachmann (34). By kind permission of the Egyptian Ministry of Scientific Researches, a number of radial velocity programmes is being carried out with the 74-inch (r88 em) reflector at Kottamia, U.A.R., in collaboration with the staff at that Observatory. These include the report on RR Lyrae stars (Woolley and Aly) mentioned above. In addition the following programmes continue:

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·s

(a) Observations of semi-regular variables brighter than 11 1'flpg not listed in Wilson's Catalogue. (b) Spectroscopic binaries with unknown orbital elements between 7·5 and u·s 1'flpg· (c) Ao stars in the north galactic cap ( oc = uh oom to 14h 30m, 8 = + I0° to + 50°, 19oo·o), which are in the HD but not in Wilson's Catalogue. Preliminary results from this programme were presented at IAU Symposium No. 30 at Toronto (Woolley, Aly and Asaad {I)). (d) Ko stars taken from the HD catalogue which have no known radial velocity, in the areas QC = 3h zorn tO 5h zorn 0 = + 10° tO +Z0° (1900•0) 6h oom to 8h oom +33° to +43° 18h 10m to zoh 1om + 55° to +65° z1h 15m to ooh 15m +Z9° to +39° (e) Members of Gliese's catalogue of stars within zo parsecs, brighter than u·s mpg and north of -30°, with no known radial velocity. In August-September 1966, Woolley and Palmer undertook a programme of observations of W Virginis variables, using the 100-inch (z54 em) Newtonian spectrograph at the Mount Wilson and Palomar Observatories. A line-scanning measuring machine developed in the Observatory workshops has been brought into use.

Marseilles and Haute-Provence Observatories The delegation attending the Toronto Symposium, headed by Fehrenbach gave a general summary of the work undertaken with the various objective prism telescopes since its inception {I). The publication of some of the work has had to wait for the establishment of satisfactory reference star velocities in the areas. Among galactic fields studied, those numbered 5- I 5 and I-M, together with the special fields designated 8 Tau, P Cygni, hand x Persei, and Praesepe have been published. All these, with the exception of the last named, have been observed with the small objective prism (PPO) at Haute-Provence. Results for twenty Selected Areas, observed with the small objective prism, and, in three cases, reobserved with the large objective prism, have been published. These results are included in the Draft Report of Commission 33 (Committee on Selected Areas), where the reference numbers of Selected Areas under study are given. Here also are listed the names of the Parenago areas now being studied with the large objective prism (GPO 3), and that one, (5h 561!1o, +z7o 34'), already published, for which the plates were taken with the small objective prism. References additional to those previously published are Rebeirot (35), Fehrenbach et al. (36). Mme Rebeirot and Imbert have published a trial list of velocities (33 stars and two standards) obtained with the short focus (F/I ·1) camera of the Haute-Provence coude spectrograph (37).

La Plata Observatory Radial velocities have been determined for the following stars: HD698 (Spectroscopic binary: Sahade (38)); V 453 Scorpii (eclipsing variable: Sahade and Frieboes-Conde (39)); 17 Leporis (peculiar star, spectroscopic binary, late-type component: Ringuelet-Kaswalder, Sahade and Wallerstein (4o)). Stars in course of measurement are the following: 8 Librae: All the material from Allegheny, Michigan and Mount Wilson is being remeasured by Sahade, Hernandez, Fay and Cohen. WY Velorum, symbiotic star, is being studied by Sahade and Hernandez, who are also studying the red region of f3 Lyrae.

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The eclipsing variable E Coronae Austrinae is being studied by Sahade, Hernandez, Sister6 and Ringuelet-Kaswalder. PGC 4444 ( =HD 159 176), a sixth magnitude spectroscopic binary Oe 5 star, for which an orbit was given by Trumpler, is being reinvestigated by Hernandez. Sahade presented a paper to the Toronto Symposium under the title 'A systematic effect in the radial velocities determined with an oscilloscope-type comparator' (x). Radcliffe Observatory, Pretoria

(1) B Stars: A fourth list of radial velocities of southern B stars has been published (41). This comprises 73 stars, (including 19 faint companions of visual binaries) selected as members of the Scorpio-Centaurus association. As reported to IAU Symposium No. 30 by Thackeray (x), these velocities strongly confirm the concept of group motion, but the radial velocities alone do not determine a convergent with sufficient precision to derive a K-term. The existence or otherwise of a K-term must be decided by determining a convergent from more accurate proper motions. Feast and Shuttleworth have published extensive analyses of radial velocities of OB stars, Cepheids and clusters (42, 43). Velocity dispersions of the various objects, including interstellar gas are compared. A statistical correction for distances of B stars, (which becomes serious beyond 3 kpc), is determined. Thew (R) curve agrees well with the 21 em curve after this correction is applied. A value of A = 14·3 ± o·8 km s-1 kpc-1 is derived, and R0 = 9"5 ± 1·o kpc. Feast and Thackeray (44), point out that the w (R) curve derived by Miinch and Miinch can be seriously affected by such statistical corrections to the distances of the stars used. Thackeray (45, 46) has observed radial velocities of eight 9th-magnitude stars for comparison with objective prism velocities by the Fehrenbach group. A programme is being initiated to observe radial velocities of the remaining 150 early-type southern stars brighter than 7"5 m with unknown radial velocities. Graham, now at Kitt Peak National Observatory, has discussed nine distant B-type stars in Ara for which radial velocity material was obtained at Pretoria and concludes that the ratio of total to selective absorption is smaller than previously believed (47). (2) Me variables: Feast (48) has completed an important programme on 51 Me and 2 Se variables towards the galactic centre. The large velocity dispersion and steep velocity gradient with longitude across the galactic centre is closely similar to that exhibited by the planetary nebulae. The velocity dispersion is related to period in the same way as for Me variables in the solar neighbourhood. Feast (49, so), has disproved the suspected presence of any Me variable in a globular cluster with period appreciably greater than 200 days. This strengthens the belief that there is no essential difference between the Me variables in globular clusters and in the general field. CH Set (period: 190·6 days), has been shown to belong to the globular cluster NGC6712 despite some opinions to the contrary (51). Feast is currently observing velocities of semi-regular and S-type variables. (3) Cepheids: Feast (52) has completed observations of distant (2·5 to 4"5 kpc) cepheids = 290°. Velocity curves are derived for 10 cepheids, while observations near maximum near light have also been secured for 11 other faint cepheids. The results, compared with velocities of OB stars and H 1 gas in the same region, confirm the concept of large-scale regional motions which produce humps in the w(R) curve. A value of R0 = 9·8 ± 1·4 kpc is derived. T. Lloyd Evans is reobserving some southern cepheids for radial velocity, especially V 636 Sco, whose y-velocity seems to have changed.

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M. Breger has observed the cepheids U Sgr and S Nor at 29Ajmm throughout their cycles. He also observed the f3C Ma variable, rx Lup, as well as the variable velocity star, f3 Cen, which is also suspected to be of this or a closely related class (53). (4) Clusters: Thackeray and Wesselink (54) have published radial velocities of stars in the so-called cluster IC2944. No clear-cut variation of velocity with magnitude is found. The uncorrected velocity dispersion in this young cluster is 6·4 krn s-1 • Evidence of expanding gas around the cluster is found. T. Lloyd Evans is observing radial velocities in NGC 6383 and IC 2581. (5) Binaries: Orbits of six double-lined spectroscopic binaries of early type have been published: HD14ooo8, 178322 (55); o Pic (56); HD147971, 75759 (57); HD175544 (58). Two of these were Radcliffe discoveries, and two more recent discoveries (HDro4631, 161 756), are being investigated. Other binaries under investigation include HD101 131, 101205, (in IC2944), 93403, 136504, 142096, 155775, and HDr61783 (59, 6o). Sher observed a number of suspected binaries of relatively small amplitude belonging to the Sco-Cen association. Feast has studied the remarkable supergiant eclipsing system BL Tel (61), a high-velocity star out of the galactic plane. Thackeray (62) observed S Equ during eclipse and found satellite lines during partial phases. Spectroscopic observations of this star have been continued for Dr M. Plavec. (6) Miscellaneous: Thackeray (63) has shown that the [Fe II] lines observed during a remarkably deep minimum of S Dor fix the zero-point for radial velocity in the P Cyg contours shown by permitted lines. This radial velocity agrees closely with the mean velocity for the relevant part of the LMC. Feast has obtained spectra of 10 planetary nebulae in the Large Cloud and obtained evidence of rotation and an indication of velocity dispersion from them (64). Friedjung (65) has measured widths of emission lines in RR Tel and interpreted them in terms of his model for continuous ejection of gas from novae. Slit spectra of stars discovered by the Fehrenbach group as having large radial velocity in the neighbourhood of the Large Magellanic Cloud have proved some of these stars to belong to the galactic foreground, e.g. two sub-dwarfs (66). Daylight spectra of Cornet Ikeya-Seki near perihelion showed large velocity shifts, corresponding to the motion towards the Sun for reflection from the nucleus, and to the motion of the cornet relative to the Earth for cometary emission of Fe I, Ca II etc. (67). In a recent note Thackeray reports a radial velocity for Proxima Centauri based on emission line measures. The mean value - 15 ·7 ± 3 ·3 krn s-1, is 7 krn s-1 different from that of rx Cen but this is not necessarily significant (68). Thackeray has rerneasured some B-type spectra with oscilloscope projection machines and finds that, at least for his measures of diffuse lines, two-way measures are essential to avoid systematic errors. This bears out the experience of Abt (69). Observatoire de Toulouse

La recherche d'etalons pour Ia rnesure des vitesses radiales des etoiles 0, B, A signalee dans le precedent rapport a ete poursuivie avec le spectrographe a fente, C, de l'Observatoire de Haute-Provence. Le nornbre considerable de spectres a rnesurer n'a pas encore perrnis, cornrne nous 1' esperions, de publier des resultats. La methode consiste en effet a comparer 2 a 2 les 14 spectres pris en quelques minutes sur une etoile brillante de type 0, B, ou A. Dans le cas ou la vitesse radiale relative est nulle, la mesure absolue de cette vitesse est alors faite sur les 14 spectres.

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Des variations inopinees de vitesse radiale ayant ete mises en evidence sur plusieurs etoiles, il convient de controler ces variations a partir de nouveaux spectres. Ce n'est que lorsque ce travail d'ensemble sera termine que nous pourrons en faire connaitre les conclusions. En ce qui concerne les binaires spectroscopiques la mise ajour du catalogue complementaire a ete continuee. Comme les references correspondantes n'ont jamais ete publiees dans les 'Draft Reports', une liste complete des contributions de Bouigue, Bouigue et Chapuis, et Pedoussaut (I952-64), est donnee, qui pourra rendre service aux utilisateurs (76-77).

U.S.S.R. observatories Professor E. K. Kharadze reports as follows: R. Kh. Salman-Zade of the astronomical observatory of Leningrad State University has proposed an improved sheme, suitable for large batches of material, for the calculation of corrections for the diurnal and orbital motions of the observer in the reduction of radial velocities to the Sun (78). R. E. Gershberg and P. V. Shcheglov of the Crimean Astrophysical Observatory, developing a method used by Courtes, have used a Fabry-Perot etalon, combined with an interference filter centred at Hoc, and a contact image tube. They have determined radial velocities and internal motions in six gaseous objects, NGCI976, 6523, 66I8, 7000, 7822 and ICI3I8a. The plates were standardized by means of images from a hydrogen discharge tube (79). L. V. Mirzoyan and E. S. Kazarian have analysed radial velocity data for the 0-B stars, long period cepheids and interstellar gas, and have found a negative K-term attributed to non-stationary motions in the Galaxy (So).

Sonnenborgh Observatory, Utrecht Professor Anne B. Underhill reports a study of the 09 V star, Io Lacertae, using a series of 3oAjmm spectrograms taken in rapid succession. An abstract by Underhill and van Heiden has been published (81) and a more extended account will appear later (82). The spectra, taken at Victoria in November and December I964 seem to show a rapid and erratic variation of velocity over a range of IO km s-1 although the individual probable error of a single spectrogram is only 2 km s-1 • This is accompanied by rapid changes in the strength and shape of weak lines such as those of 0 II and Fe III. The radial velocities are dependent on measures of the strong lines, chiefly those of H and He I, and changes in them are not so easily observed because of saturation. From the astrophysical standpoint it seems important to repeat these observations with more powerful spectrographic equipment in order to discover what variations of velocity do occur within intervals of less than IO minutes in the atmosphere of this standard, rather sharp-lined 09 V star. De Groot, van Heiden and Underhill hope to pursue further the radial velocity observation of stars in the direction of IC8o5 reported in preliminary form at Toronto (1).

Dominion Astrophysical Observatory, Victoria B.C. General: Radial-velocity observations have continued of clusters, spectroscopic binaries and visual binaries. Results on clusters are being reported to Commission 37. Orbital elements have been determined for t 1 Ursae Majoris, v Ophiuchi (83, 84); 47 Andromeda (85), and HDI7 5544 (58). Radial velocities of visual binaries have not yet been published. At the suggestion of Dr Thackeray, a co-operative Victoria-Pretoria programme has been undertaken by Batten and Thackeray to determine radial velocities of I I bright B8-B9 stars. The aim is to test the apparent correlation between K-term and quality of velocity-determination discussed

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by Boulon at the Hamburg General Assembly. Observations are complete, hut measures have not yet been made. Derivation of galactic-rotation constants from the results of the B star radial-velocity programme was completed by R. M. Petrie before his death, and will be published. Wavelengths: Selection of wavelengths suitable for velocity measures of G and K spectra was completed by R. M. Petrie shortly before his death, for the highest dispersion (2·xAjmm), available at the coude focus of the 48-inch ( 122 em) telescope. It is planned to extend this work to earlier spectral types as soon as possible. J. M. Fletcher is studying the selection of wavelengths, suitable for all spectral types, at the dispersion of 5 and xoAfmm, also available at the coude focus. A. H. Batten has been studying the problem of wavelengths in 0-type spectra, mainly with reference to the Victoria IM dispersion (3oAjmm at Hy). A preliminary report has been published (86) and the work is continuing. Accuracy of coude-spectrographs: Study of the problems reported by Dr Petrie at Hamburg was continued by him until his death, and since then, by Fletcher. Fletcher reported on his progress at the Toronto Symposium {I). It appears that the relatively large external errors encountered in coude spectrographs are due, at least partly, to non-uniform illumination of the collimator arising from failure to achieve exact focus of the stellar image on the slit, or possible from imperfections in the primary mirror of the telescope. It is also important to maintain long-term stability of all parts of the spectrograph. Investigation is continuing to try to estimate the relative importance of these two effects and to ensure that the maximum accuracy of which the spectrograph appears to be capable (m.e. of single plate ,....., ± o·o7 km s-1 for solar-type spectra) is available at all times. Systematic Errors in Measurement of Double-Line Spectroscopic Binaries: Reports on this work have been presented by Petrie and Andrews (87) and by Petrie, Andrews, and Scarfe {I). It appears that systematic errors may be made in the measurement of double-line binaries, especially when oscilloscope devices are used to measure the plates. In extreme cases, errors of up to so% may occur in the determination of the total mass of a binary system. CONCLUSION

To all appearances the work covered by the field of the Commission is in a healthy state, but in spite of this there is some cause for concern. The determination of radial velocities yields fundamental astronomical data, without which our theoretical understanding of stellar motions and galactic structure would be paralysed. It is essential that this work be continued, and the discussions at Toronto, and the content of the foregoing report, make it clear that those active in the field are well aware of what needs to be done for objects ranging from the brightest stars to the faintest quasars, and of all population and morphological classifications. Much of the work is still undertaken by classical methods, using photographic plates and slit spectrographs. It is clear that this style of work will remain indispensable for a long time to come. It is a source of great satisfaction to see new methods introduced, such as the photoelectric method of Griffin, the application of image tubes by Lynds, Mrs Rubin and others, and the scanning technique of de Vaucouleurs. The invention of new methods is, however, of little significance unless they are applied on a considerable scale. The example of the work of Fehrenbach's school shows how much meticulous effort needs to be expended on the development of a new technique before it becomes fully productive. The attendance roll at the Toronto Symposium demonstrated that radial velocity work is being supported by a rather small number of observatories in rather few countries. The analysis presented by Weaver shows, that, certainly when classical methods are employed, it is an essential condition for the production of accurate results that the work be planned on a large scale, and be long continued. Only when a number of observers cooperate, in a long programme, using a spectrograph of which the essential adjustments are left undisturbed, is it

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usually possible to evaluate with certainty the various systematic and accidental errors for which corrections must be applied. If the equipment is especially designed so as to permit changes from one dispersion to another without modification of the basic adjustments, as is the case for example with the Haute-Provence coude spectrograph, versatility of equipment can be reconciled with this basic requirement. If the design necessitates an actual removal and remounting of the dispersing elements each time a new dispersion is required, then there can be erratic changes of zero-point in the velocity system between one observing run and another, a matter stressed by Edmondson in his contribution to the Toronto Symposium. These requirements of stability and continuity have meant that successful radial velocity work has usually been confined to those observatories, among which government observatories are the prime example, where long-term routine work can be undertaken. University observatories, catering for the needs of doctoral candidates, have often been less successful in this field. They are more often concerned with versatility in their equipment, and the provision of opportunities for the demonstration of originality on the part of their students within the time-limits for the production of their theses. The production of a considerable number of new and accurate radial velocities is an undoubted contribution to astronomy, but it may not be regarded as a sufficiently original contribution to an academic thesis. Among astronomers influential in the formulation of astronomical policy there is sometimes a feeling that the two types of requirement are in conflict. It should be no harder to reconcile them in radial velocity work than it is in any other field of astronomy, or indeed, in any other field of science where a number of workers have to share large and expensive equipment. It is, however, highly desirable that some kind of solution be found within the field of work of Commission 30. Unless this is done, the number of observatories participating effectively in radial velocity work is unlikely to increase, and the recruitment of younger astronomers to an interest in the field is likely to suffer. A possible solution in the case of university departments would be for graduate students to pool their requirements in a common programme. They would also pool their observing resources, so that each observer contributed to the programme as a whole, and not merely to that section of it in which he was personally interested. When the individuals came to draw from the pool of results those pertaining to their own programmes, they would obtain measures made under the most favourable conditions all around the sky, and subject to the running statistical control on errors derived from a study of the entire pool. Commission 30 shares with a number of others the characteristic that it is built round a single basic astronomical operation, of which the fundamental principles have been established for a very long time. The data produced are essential, and there is no question that the basic operations need to be continued for the forseeable future. There is a need to maintain them in institutions which are already active and to introduce them on the necessary scale into others. DAVID S. EVANS

Acting President of the Commission REFERENCES I.

2.

3· 4· 5· 6.

Report of !AU Symposium No. 30, edited by J. F. Heard and A. H. Batten. Academic Press, London, 1967. Griffin, R. F. A photoelectric radial-velocity spectrometer, Astrophys. J. (in press). Griffin, R. F. 1966, The spectroscopic binary 73 Leonis, Observatory, 86, 145. Mowat, M. Optical Determination of Distant Objects, Symposium on Radio and Optical Studies of the Galaxy, p. 100, Mount Stromlo Observatory, May 1966. Bok, B. J., Gollnow, H., Hindman, J, V., Mowat, M. 1964, Radial Velocities associated with Selected Emission Nebulae in the S.M. C., Austr. J. Phys., 17, 404. Buscombe, W., Kennedy P. M. 1962, Two B-Type Spectroscopic Binaries, Publ. astr. Soc. Pacij., 74, 323.

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7· Westerlund, B. E., Danziger, I. J., Graham, J. I963, Supergiant Stars in the Wing of the Small Magellanic Cloud, Observatory, 83, 74· I963, Radial velocities of Bright Southern Stars, III, Mon. Not. R. astr. 8. Buscombe, W. Soc., 126, 29. 9· Kennedy, P. M., Przybylski, A. I963, Radial velocities of so high velocity stars, Mon. Not. R. astr. Soc., I26, 381. IO. Buscombe, W. I965, Stellar Spectra in Galactic Cluster IC239I, Mon. Not. R. astr. Soc., I29, 4I I. II, Buscombe, W. I965, The Scorpio-Centaurus Association (Paper V), Irish astr. J., 7, 63. I2. Buscombe, W., Kennedy, P. M. I965, Radial Velocities of zoo Southern B Stars, Mon. Not. R. astr. Soc., I30, 281. I3· Przybylski, A., Kennedy, P. M. I965, Radial Velocities and three-colour Photometry of I66 Southern Stars, Mon. Not. R. astr. Soc., I3I, 95· I4. Przybylski, A., Kennedy, P. M. I965, Radial Velocities and three-colour Photometry of 52 Stars with large Proper Motions, Mon. Not. R. astr. Soc., I29, 63. Radial Velocities in the Magellanic Clouds, Symposium on the Magellanic IS. Gollnow, H. Clouds, p. I2, Mount Stromlo Observatory, May I965. I6, Buscombe, W., Kennedy, P. M. Optical Insterstellar Lines in the Southern Milky Way. Symposium on Radio and Optical Studies of the Galaxy, p. 82, Mount Stromlo Observatory, May I966. I7. Evans, D. S., Laing, J. D., Menzies, A., Stoy, R. H. I964, Fundamental Data for Southern Stars (Fifth List). R. Obs. Bull. no. 85. IS. Evans, D. S. I966, Fundamental Data for Southern Stars (Sixth List). R. Obs. Bull. no. IIO. I9. Evans, D. S. et al. R. Obs. Bull. (in press). 20. Evans, D. S., Young, A. T. I966, A Technique for Period Finding. Observatory, 86, zoo. 2I. Lafler, J., Kinman, T. D. I965, Astrophys. J., Suppl., II, I99· 22. Evans, D. S., Malin, S. R. I965, Radial Velocities of Southern Galaxies. II. Mon. Notes astr. Soc. Sth. Afr., 24, 32. 23. Evans, D. S. I965, A Note on HR5527 = HD13070I/2: Mon. Notes astr. Soc. Sth. Afr., 24, I 1. 24. Jones, D. H. P. Personal communication. 25. Wayman, P. A. I96I, Appendix to Fundamental Data for Southern Stars. IV. R. Obs. Bull. no. 48. 26. Jones, D. H. P., Lagerweij, H. C. The 13 Scuti variable I Monocerotis. Mon. Notes astr. Soc. Sth. Afr., (in press). 27. Heard, J. F. I965, Pub!. Dom. astrophys. Obs., 2, 443· 28. Wayman, P. A. Personal communication. I965, Radial Velocities of 96 stars derived from 29. Woolley, R. v. d. R., Harding, G. A. 241 spectra obtained with the coude spectrographs at Mount Wilson and Palomar and Radcliffe Observatories. R. Obs. Bull. no. 93· 30. Harding, G. A. I965, Radial Velocities of bright members of the globular cluster w Centauri. R. Obs. Bull. no. 99· 3I, Woolley, R. v. d. R., Aly, K. I966, Radial Velocity observations of RR Lyrae variables. R. Obs. Bull. no. I I4. The Radial Velocities, 32. Jones, D. H. P., Palmer, D. R., Walker, E. N., Wallis, R. E. Spectral Types and Projected Rotational Velocities of Six Hundred Bright Northern A Stars. R. Obs. Bull. (in press). 33· Harding, G. A., Palmer, D. R., Pope, J. D. R. Obs. Bull. (in press). 34· Wachmann, A. A. I966, IAU lnf. Bull. Var. Stars, no. IJ8. 35· Rebeirot, E. La mesure des vitesses radiales au prisme objectif, XVIII. Classifications spectrales et mesures de vitesses radiales de 112 etoiles situees dans Praesepe. Pub!. Obs. Hte-Provence, 8, no. 24, I966; J. Observateurs, 49, no. 4-5. 36, Fehrenbach, Ch., et al. La mesure des vitesses radiales au prisme objectif, XIX. Liste de 893 vitesses radiales determinees au prisme objectif a vision directe. Pub!. Obs. HteProvence, 8, no. 25, I966; J. Observateurs, 49, no. 4-5.

VITESSES RADIALES

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1965, Vitesses radiales obtenues avec Ia chambre I du spectro37· Rebeirot, E., lmbert, M. graphe coude de l'Observatoire de Haute-Provence. Publ. Obs. Hte-Provence, 8, no. 6; J. Observateurs, 48, 153. 38. Sahade, J. 1966, Modern Astrophysics, M. Hack, ed. (Paris: Gauthier-Villars), p. 219. 39· Sahade, J., Frieboes-Conde, H. 1965, Astrophys. J., 141, 652. 40. Ringuelet-Kaswalder, A., Sahade, J., Wallerstein, G. 1965, Assoc. argent. Astr. Bol., no. 8-9-10, 32. 41. Thackeray, A. D. 1966, Radial Velocities of Southern B Stars, IV. The Sco-Cen Association. Mem. R. astr. Soc., 70, 73· 1965, Kinematics of B stars, Cepheids, Galactic 42. Feast, M. W., Shuttleworth, M. Clusters and Interstellar Gas in the Galaxy. Mon. Not. R. astr. Soc., 130, 245. 43· Feast, M. W., Shuttleworth, M. 1966, Mon. Not. R. astr. Soc., 134, 107. 1965, Rotation of Inner Parts of the Galactic System 44· Feast, M. W., Thackeray, A. D. as determined from OB Stars. Astrophys. J., 142, 1645. 45· Thackeray, A. D. 1964, Radial Velocities of 5 Stars. Mon. Notes astr. Soc. Sth. Ajr., 23, 8I. 46. Thackeray, A. D. 1966, Radial Velocities of 3 Stars. Mon. Notes astr. Soc. Sth. Ajr., 25, 35· 47• Graham, J. A. Observations of some distant B-type stars in Ara. Bull. astr. Inst. Nether/. (in press). 48. Feast, M. W. 1966, Kinematics of Me Variables towards the Galactic Centre and a Comparison with the Planetary Nebulae. Mon. Not. R. astr. Soc., 132, 495· 49· Feast, M. W. 1965, Long Period Variables in Globular Clusters and in the General Field. Observatory, 85, 16. so. Feast, M. W. 1966, Long Period Variables in the Field of Globular Clusters. Observatory, 86, 120. 51. Feast, M. W. CH Set as a Member of NGC6712 and the absolute magnitude of the Mira variables. Observatory (in press). The Radial Velocities of distant Cepheids and the distance to the Galactic 52. Feast, M. W. Centre. Mon. Not. R. astr. Soc. (in press). 53· Breger, M. A Spectroscopic Study of two Southern B-Type Variables. Mon. Not. R. astr. Soc. (in press). 54· Thackeray, A. D., Wesselink, A. J. 1965, A Photometric and Spectroscopic Study of Cluster IC2944. Mon. Not. R. astr. Soc., 131, 121. 55· Thackeray, A. D., Hutchings, J. 1965, Orbits of Two Double-lined Binaries, HD 140008 and 178322. Mon. Not. R. astr. Soc., 129, 191. 1966, The Spectroscopic Binary, 8 Pic. Mon. Not. R. astr. Soc., 131, 435· 56. Thackeray, A. D. 57· Thackeray, A. D. 1966, Orbits of Two-Double-Lined Spectroscopic Binaries. HD 147971 and 75759· Mon. Not. R. astr. Soc., 134, 97· The B-type Spectroscopic Binary HD175544. Pub/. 58. Thackeray, A. D., Tatum, J. B. Dom. astrophys. Obs. (in press). 1965, The Eclipsing Variable HD 161783 (BV 59· Thackeray, A. D., Knipe, G. F. G. 420). Mon. Notes astr. Soc. Sth. Afr., 24, 109. 6o. 1966, Ibid., Mon. Notes astr. Soc. Sth. Ajr., 25, 30. The Supergiant Eclipsing System BL Telescopii. Mon. Not. R. astr. Soc. 61. Feast, M. W. (in press). 1965, Spectra of S Equ during Eclipse. Observatory, 85, 206. 62. Thackeray, A. D. 63. Thackeray, A. D. 1965, Spectral Variations of S Dor. Mon. Not. R. astr. Soc., 129, 169. 1964, Planetary Nebulae in the Large Magellanic Cloud. Observatory, 84,266. 64. Feast, M. W. The Physical Conditions and Velocity Distribution in the Envelope of 65. Friedjung, M. RR Telescopii. Mon. Not. R. astr. Soc. (in press). 1966, Two New High Velocity Sub-dwarfs. Observatory, 86, 6o. 66. Thackeray, A. D. 67. Thackeray, A. D., Feast, M. W., Warner, B. 1966, Daytime Spectra of Comet Ikeya-Seki near Perihelion. Astrophys. J., 143, 276. Measured Radial Velocities of Proxima Centauri. Observatory, (in 68. Thackeray, A. D. press).

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69. 70. 71. 72. 73· 74 75· 76. 77· 7S. 79· So. SI. S2. S3. S4. Ss. S6. S7.

COMMISSION 30 Personal communication. Abt, H. 1952, Ann. Obs. Toulouse, :n, 31. Bouigue, R. 1954, Ibid., 22, 49· Bouigue, R. 1955, Ibid., 23, 45· Bouigue, R. 1956, Ibid., 24, 69. Bouigue, R. 1957, Ibid., 25, 69. Bouigue, R. 1959, Ann. Obs. Toulouse, 27, 87. Bouigue, R., Chapuis, J. L. 1963, Ann. Obs. Toulouse, 29, 31. Pedoussaut, A. 1964, Ibid., 30, so. Pedoussaut, A. 1966, Vestn. Leningrad. gos. Univ., p. 66. Salman-Zade, R. Kh. 1964, Astr. Zu., 41, 425. Gershberg, R. E., Shcheglov, P. V. 1965, Trans. Astrophys. Inst. Kazak Acad. Sci., s, 224Mirzoyan, L. V., Kazarian, E. S. 1966, Astr. J., 71, 183. Underhill, A. B., van Heiden, R. C. P. Bull. astr. Inst. Nether!., IS (in press). Underhill, A. B., van Heiden, R. C. P. 1965, Publ. Dom. astrophys. Obs., 12, 361. Gutman, F. 1966, Ibid., 12, 391. Gutman, F. 1964, M.Sc. thesis, Toronto, (unpublished). Fletcher, }. M. 1965, Publ. astr. Soc. Pacif., 77, 210. Batten, A. H. 1966, Astr. J., 71, 175. Petrie, R. M., Andrews, D. H.

31. COMMISSION DE L'HEURE PRESIDENT: Mr H. M. Smith, Royal Greenwich Observatory, Herstmonceux Castle, Hailsham, Sussex, England. VICE-PRESIDENT: Professor Dr N. N. Pavlov, Pulkovo Observatory, Leningrad, U.S.S.R. COMITE D'ORGANISATION: L. Essen, W. Markowitz, N. Stoyko, M. Torao, F. Zagar. MEMBRES: Abraham, Arbey, Bakulin, Belotserkovski, Billaud, Blaser, Bonanomi, Brkie, Danjon t, Decaux, Delhaye, Demetrescu, Dingle, Drambii, Dubois-Chevallier, Enslin, Fernandez de la Puentet, Fuchs, Gama, Gokmen, Gougenheim, Guinot, Hall (R. G.), Hers, Iijima, Koebcke, Lacombe, Lederle, Loron, Madwar, Melchior, Mikhailov, Miyadi, Opalski, Orte Lledo, Postoiev, Randic, Sandig, Shcheglov, Shirjaev, Sternberk, Stoyko (A.), Tagaki, Tardi, Thomson (M. M.), Tsao, Verbaandert, von der Heide. CO-ORDINATED TIME SIGNALS The recommendations of the Xth Plenary Assembly of the International Radio Consultative Committee, Geneva 1963 (Rec. 374) were further modified at the Study Group VII Interim meeting (Monte Carlo 1965) and the Xlth Plenary Assembly (Oslo 1966). The effect of the modifications has been to clarify the recommended system u.T.C. (annual offset, plus time adjustments when necessary) and to place responsibility for co-ordination on the Bureau International de l'Heure. In addition, the Oslo recommendation (Doc. VII/1012) makes formal provision for emissions with zero carrier offset but with the rate of the time signals offset, and co-ordinated with those mentioned above; also for experimental emissions in which both th~ carrier and the rate of the time signals is not offset. In the latter case time adjustments should also be co-ordinated by the BIH. At the XVth General Assembly of the International Scientific Radio Union (Munich 1966) Commission 1 expressed the opinion that all the methods of operating Standard Frequency services which have been proposed contain defects which will cause increasing difficulties as the use of the services extends; and that these services must inevitably develop towards a system of uniform atomic time and constant frequency. On the other hand, astronomers concerned with the needs of navigation consider it essential that: (a) the navigational ephemerides continue to use GMT (u.T.) as the time argument. (b) time signals, deviating by not more than 0~1 from U.T.2 continue to be available to navigators, preferably in the present form of U.T.C. If radio time signals gave only A.T., it would be necessary to communicate, at least every two months, predicted values of U.T. - A.T. by radio broadcast to navigators. This procedure is far less convenient and dependable than the communication of corrections to laboratoryborne physicists. Separate emissions of u.T. and A.T. would provide a possible solution, but might prove impracticable for economic reasons. Some dozen countries now conform to the U.T.c. co-ordination scheme, and this has led to a drastic reduction in the number of individual corrections to radio time signals published each month by the Bureau International de l'Heure. Moreover it has proved possible to reduce significantly the delay in publishing definitive corrections. A report prepared by Professor Belotserkovsky (see page 67o) describes a parallel scheme, operating in the U.S.S.R., adjacent countries and China, and co-ordinated by the Institut des Mesures Physicotechniques et Radiotechniques (IMPR). It is hoped that the two coordinating authorities, BIH and IMPR, may be able to come to some mutual understanding leading to the adoption of a single system in all radio time signal emissions. 659

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The CCIR meetings at Oslo, 1966 were attended by H. M. Smith (representing the IAU) and B. Guinot (representing the BIH). In addition to the resolutions on the U.T.c. system of time signal emissions, co-operation between CCIR, URSI, IUGG and IUPAP was proposed in pursuing studies and experiments relative to the following problems: (i) how to provide both the epoch of u.T. and the international unit of time interval in the same emission; (ii) how the various essential requirements could be met by the emission of a single uniform time scale. Reference was also made to the continuing problem of interference, both mutual and from other emissions, experienced on standard frequency and time signal services, particularly in the European area. This matter also received attention at the URSI meetings at Munich, 1966 and it is hoped that the various authorities concerned will be able to come to a satisfactory solution. The CCIR recommended that emitted frequencies should now be maintained constant to ± 1 x xo-1 0, which corresponds to a uniformity in the rate of the time signals of about xo microseconds per day. The tabulated data on standard frequency and time signal emissions was brought up-to-date and the assistance of all authorities responsible is requested in ensuring that all changes in emission schedules are notified. DEFINITION OF THE SECOND

A further step was taken by the Twelfth General Conference of Weights and Measures (October 1964) towards the definition of the second in terms of an atomic resonance. In recent years, it has been increasingly realized that the second of u. T .2 is unsuitable, owing to its inherent variability, as the basic unit of time interval. The second of E. T ., though by definition invariable, is not readily accessible, and is therefore equally unacceptable. Progress in the development of atomic standards of frequency has demonstrated that these may now be used to make available an accurate and convenient unit of time interval. Continuously running atomic standards of frequency may also be used for the establishment of a uniform time scale. The Twelfth General Conference of Weights and Measures considering the urgency of arriving at an atomic or molecular standard of time interval for the needs of precise metrology and that, in spite of the results obtained in the use of caesium as an atomic frequency standard, the moment has not yet come for the General Conference to adopt a new definition of the second because of new and important progress which may arise from current researches, authorised the International Committee of Weights and Measures to designate atomic or molecular standards of frequency to be employed temporarily. The committee declared that the standard to be so employed is the transition between the hyperfine levels F = 4, MF = o and F = 3, MF = o of the fundamental state 2S! of the atom of caesium 133, not perturbed by external fields, and that the value of 9 192 631 770 hertz is assigned to the frequency of this transition. It will be noted that the caesium frequency adopted is that determined in 1958, (Markowitz, Hall, Essen and Parry. Phys. Rev. Lett., I, 105, 1958), and now in general use. Recent redeterminations which take account of the effects of the adoption of the revised system of astronomical constants have shown that there is no practical need to revise this value (e.g. Nicholson and Sadler, Nature, 210, 187, 1966). At this stage the choice of caesium as an interim standard is favoured on practical grounds: there are many caesium standards in use in many different countries; comparisons between caesium standards of slightly different construction exhibit no significant frequency deviations.

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It is not certain that caesium may be the best final choice, as the stabilities now believed to be obtainable under laboratory conditions (month long samples) are quoted by R. F. C. Vessot (Varian Associates) as Rubidium gas cell 5 X I0-11 3 X 10-12 Caesium beam 3 X 10-!4 Hydrogen maser On the astronomical side it is anticipated that a more accurate relationship between atomic frequencies and the second of E.T. may be possible within the next few years. There are various complications: it has been suggested that relativistic gravitational effects on quantum transitions may produce a periodic term between A.T. and E.T. with an amplitude of 3 x 10-10 and a period of one year, (S. Aoki, Astr. J., 69, 221, 1964): there are reasons to suppose that there may be an acceleration between A.T. and E.T. On the other hand, the linking of A.T. and E.T., both in the unit of time interval and in epoch, might be a useful simplification and, as the astronomer only requires E.T. to an accuracy of about o·1 seconds, tolerable mutual departures should be achieved without further adjustment for many decades. THE EPOCH OF EPHEMERIS TIME

The formal definition of the epoch of Ephemeris Time, as adopted by the General Assembly in 1958 (Trans. !AU, xo, 72, 1960, Resolution No. 2) on the recommendation of Commissions 4 and 31, specifies the measure of E.T. at the instant at which the geometric mean longitude of the Sun was 279° 41' 48'fo4. However, as subsequently pointed out by Professor Danjon and incorporated in the report of the meetings of Commission 4 (Zoe. cit. p. 97), this definition depends on the adopted value of the constant of aberration. The IAU system of Astronomical Constants (Trans. !AU, 12, 593, 1966), which was adopted by the Twelfth General Assembly in Hamburg (Zoe. cit., p. 95, Resolution No.4), introduces a change in the adopted value of the constant of aberration from 20'!47 to 2o'f496. It would appear that, to accord strictly with the formal definition, it is necessary to increase the measure of E.T. at any instant by + o~63, to apply a correction of - o'f346 to the mean longitude of the Moon, and to apply smaller (but more complicated) corrections to the ephemerides of the planets. Pending consideration of the possibility of revising the definition these corrections have not been incorporated into the national and international ephemerides for I968. There are several alternative possibilities, one of which is, of course, to adhere strictly to the present definition; these possibilities are being examined by Commission 4 and its considered recommendation will certainly be the subject of discussion with Commission 3 I in Prague. If a revised form of definition is recommended, it may be possible and desirable to specify the numerical constants in the definitions of the epochs of both Ephemeris Time and Atomic Time in such a way that the two scales can be linked as precisely as their characteristics allow. TRAVELLING CLOCK EXPERIMENTS

The feasibility of transporting clocks by air in order to make microsecond comparisons between standard clocks in widely separated locations was first demonstrated by Reder and Winkler in I959· Since then, a number of quartz and caesium clocks have been used to make precise comparisons between selected pairs of establishments. In addition, the Hewlett Packard Co. have made tours which have included a number of establishments in the U.S.A. and in Europe. In I964 comparisons were made between U.S.A. and Switzerland. In February-March I965, a similar experiment included comparisons at 2I establishments in I I different countries.

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The synchronization between California and Japan was also verified by a U.S. Navy experiment employing artificial satellite Relay II. In May-June I966 a further tour by Hewlett Packard caesium standards embraced 25 establishments in I2 different countries. Comparisons with local standards were made to accuracies of the order of o·I microseconds, and the closing error, after one month, was less than one microsecond. TRAVEL TIME OF RADIO TIME SIGNALS

Direct comparisons between clocks at distant stations, established to microsecond accuracy by means of flying clocks, permit the measurement of travel times of radio time signals and hence the determination of the effective speed of propagation, assuming a great-circle route. In this way trans-Atlantic speeds have been determined at I5 MHz (using WWV) and for VLF radio time signals. Great care must be taken to measure all lags associated with reception and measurement. In general the results for HF emissions (Band 7) confirm the extensive series of tests carried out by the Tokyo Astronomical Observatory. An attempt to measure LF travel times between European stations which had been linked by the I966 Hewlett Packard flying clock programme proved disappointing, owing to the errors of reception and measurement which are of overriding importance in view of the short radio paths involved. For VLF signals useful supplementary information has been obtained from an extensive study undertaken by the Royal Aircraft Establishment, Farnborough, England, in connection with VLF aircraft navigational aids. For this purpose, phase velocity is of interest, whereas for time service applications it is the group velocity which is important. Results in the IO-I4 kHz band are scheduled for publication by Burgess and Rawles in Radio Science. From results so far available, it appears that for a path over the sea, the effective propagation speed at I6 kHz is 298 kmfms. REPORTS OF OBSERVATORIES AND LABORATORIES

Australia. Canberra

The Mt Stromlo Observatory clock equipment has been rebuilt so that linear phase comparators continuously record the minor differences between co-ordinated systems. New crystals, VLF tracking receivers, steerable antenna and emergency power plant have been installed. A caesium beam frequency standard is on order. Continuous comparisions by landline are made with a rubidium frequency standard at the tracking station D.S.I.F. 42. Mention should be made of recent progress by independent collaborating organizations. This was discussed at a Symposium on Time and Frequency that was held at the Observatory on 7 and 8 October I965. The Postmaster-General's Department now maintains continuous time signal transmissions from VNG, Lyndhurst, Victoria. The Weapons Research Establishment, Salisbury, South Australia makes comparisons of VNG, VHP and WWVH, which are sent to the BIH. The National Standards Laboratory, Sydney, is building two hydrogen masers.

(I) Instruments:

Belgium. Uccle

Les observations a !'astrolabe Danjon, en service depuis juillet I962, sont intensifiees depuis janvier I965. Les enregistrements des observations astronomiques se font sur des chronographes electroniques perforateurs ATEA (de construction beige) qui assurent le millieme de seconde. Nous disposons depuis I960 de 2 oscillateurs a quartz, I MHz, Rohde et Schwarz. Les receptions horaires se font sur oscilloscope au o~oooi depuis le I5 fevrier I965. Un recepteur 'Racal' de Io kHz a 30 MHz est en service depuis I965.

(2) Publications: (i) L'installation de I' astrolabe Danjon toire Royal de Belgique, no. 230, I964.

a Uccle, par P. Sanders, Communication de l'Observa-

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(ii) Deduction du phenomene de precession-nutation a partir de la maree terrestre, par P. Melchior, Academie Royale de Belgique, Bulletin de la Classe des Sciences, 5eme Serie, 51, no. I, 24, 1965. Brazil. Sao Paulo Observations are made with a Danjon astrolabe (OPL 33). The equipment in use includes two Sulzer-Hewlett-Packard quartz clocks, printing chronograph Belin, radio-receiver Collins, integrating chronograph by Ebauches, a Rubidium Frequency Standard (General Technology) and a Dymec VLF receiver. The last three instruments are not yet in regular use. The reductions are performed on an IBM I62o computer owned by the S.P. University. Observational programme contains I I groups with 26-28 passages each. The list of stars contains 279 FK4 and 13 FK{ Sup. stars. Regular reporting to the BIH is delayed by acute shortage of observing and auxiliary personnel.

Canada. Ottawa The former transit and meridian circle rooms have been combined into a thermally controlled time laboratory. A commercially built caesium clock provides a frequency reference to a part in 1011• Its performance is compared daily with the long beam at the National Research Council. Time signal emissions CHU have remained unchanged except for a rubidium vapour atomic standard for direct control of frequency. Voice announcement of time each minute is made in both French and English. Time and Latitude bulletins are published quarterly.

Czechoslovakia. Prague A new method for the microsecond clock comparison was developed by the Institute of the Radioelectronics and the Astronomical Institute (both of the Czechoslovak Academy of Sciences) and verified in November, I965 between Prague and Potsdam. Being fully compatible with the ordinary TV transmission the method is based on the use of TV frame-synchronizing pulses. The regular comparisons of the main clocks in Prague and Potsdam are made weekly since January 1966.

France. Besanfon jlfodification dans l' equipement du service: On a installe deux nouveaux etalons de 'frequence; une horloge Sulzer (2, 5 MHz); un garde-temps Hewlett Packard (5 MHz); un. chronographe totalisateur Ebauches; utilisation d'un oscilloscope bi-courbe permettant la mesure des signaux horaires a l'aide d'un signal de reference.

Recherches et experiences: Mesure des temperatures a la surface du prisme de !'astrolabe a l'aide de thermistances; etude speciale du signal HBG emis par l'Observatoire de Neuchatel; etude de !'evolution du T.U.2 mesure a Besan 0° and of outward motions for l < 0°. The velocity ellipsoid of Me variables was also studied. Schlesinger (42) found that the velocity dispersion of metallic-line A-stars is similar to that of the normal A-stars. The velocity ellipsoid of subdwarfs was investigated by Takayanagi (43). Pavlovskaya (44) determined the velocity ellipsoids of stars of various spectral and luminosity classes. Dahn (45) studied the velocity ellipsoid of carbon stars. Rudnicki (46) found that carbon stars far from the galactic plane have larger velocity dispersion.

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An increase of the velocity dispersion of main sequence stars with height above the galactic plane was found by Murray (47) from a study of proper motions of field stars near M 67. He suggested that most bright red stars and many stars of intermediate colors are distant halo stars. Similar results were found by Cannon for field stars near NGC 752. The kinematics of Mira variables was studied by Smak and Preston (48). They derived values of A ranging from 15 to 25. Work on proper motions and radial velocities of RR Lyrae variables has been done by Woolley, Harding, Cassells, Saunders, Aly and Clube (49, so, 51). This work continues with the aim of finding the orbital elements as functions of the metal abundances, period of the variables, etc. Further work is being done on semi-regular variables. Van Herk (52) also made an extensive study of the motions of RR Lyrae variables. A study of the motions of bright A and gK stars near the galactic equator has been made by Eelsalu and Joeveer (53); in particular they determined the dispersion of velocities in the z-direction. Shatsova (54) proposed a Planck law to describe the distribution of stellar velocities. A truncated Schwarzschild distribution of velocities was used by King (55), Bouvier (56) and others. Dzigvashvili (57) determined the parameters of the velocity ellipsoid and the rotation velocity according to Chandrasekhar's theory. Motions of high velocity stars have been determined by Kennedy and Przybylski (58). Vitrichenko, Gershberg and Metik (59) have studied the motions of 120 high-velocity OB stars; they found that probably all of them originated in groups of hot stars. Blaauw is investigating the distribution and kinematics of intermediate age G and K giants in collaboration with the Leander McCormick Observatory. The kinematics of the Gould belt has been studied by Bonneau (30) and by Blaauw (6o). Blaauw found from a study of the velocity gradients of the stars in different directions that, about 40 million years ago, the prestellar gas probably occupied a small volume. This work continues, together with Lesh. Clube (61) found that streaming motions associated with the Gould belt may change appreciably the kinematics of nearby low velocity stars. Mouchet (62) and Martinet (63) have found, from kinematic properties of peculiar A stars, indications that these stars are connected with the Gould Belt. A few theoretical papers by Nahon (64) and Massonie (65, 66) deal with an application of the least squares method to the analysis of the radial velocities, the distribution of errors and the influence of selection on the determination of mean velocities. Kinematics, Age and Chemical Composition General articles on the connection between the kinematic properties of stars, age, and chemical composition were given by Delhaye (1), Cayrel and Kovalevsky (67) and Cayrel (68). Eggen (69, 70) studied the colors, luminosities and motions of more than 1000 nearby A and G stars; many of these stars belong to moving groups. He found that for stars of the same age the chemical composition may vary, but there is a rough correlation of age with metal abundance and with the space motions. The chemical composition and kinematics of disk high-velocity stars of the main sequence were considered by Stromgren (71). A strong correlation between ultraviolet excess and space motion of high-'velocity stars was found by Oosterhoff and Ponsen (72). Similar results were found by Kreiken and Yilmaz (73). A study of the kinematics of planetary nebulae, carbon stars and RV Tauri stars in connection with population type was carried out by lwanowska, Kanthak and Boenigk (74, 75, 76). A correlation between age and velocity dispersion perpendiculary to the galactic plane was found by Dennis (73a).

STRUCTURE DU SYSTEME GALACTIQUE

705

Kinematic ages of stars were found by Schmidt-Kaler (77, 78) from the distribution of different groups in the spiral arms. Connections between the orbital characteristics of the nearby stars and their ages were found by Shimizu and Takahashi (79). An explanation of the age effect was based primarily on the variation of the force field.

B. Gas Galactic Rotation- Non Circular Motions A detailed discussion of the galactic rotation curve, based on radio observations, has been given by W. W. Shane and Bieger-Smith (So). If we assume the irregularities in the rotation curve to be due to lack of hydrogen then an improbable density contrast arises. A more plausible explanation is that there are irregularities in the large-scale motions associated with the spiral structure. Stream motions in the outer edges of the arms were suggested. Such motions were found by Burton (81) in the Sagittarius arm. The discrepancy between the northern and southern velocity curves, as given by Kerr (82), was verified. Braes (83) tried to find the expansion motion suggested by Kerr, but reached a negative conclusion. The same conclusion was drawn by W. W. Shane (84). On the other hand, Locke, Galt and Costain (85) found evidence in favor of Kerr's hypothesis, from their study of the distribution of neutral hydrogen in the anticenter direction. Pismis (86) suggested that the minima in the rotation curve are due to the existence of clouds with large radial and z-motions. Dixon (87) found indications that the interstellar medium lags behind the gravitational circular velocity by 14 km s-I, because of non-gravitational forces. Agekyan, Petrovskaya and Fesenko (88) found a similar lag of 32 km s-1• They derived a galactic rotation curve below the Dutch one. Non-circular motions in the outer spiral arms were considered by Pronik (89). Detailed observations of the hydrogen velocity distribution at the anticenter have been done by Lindblad (90). Non-circular motions are apparent there. The problem of the rotation curve has been discussed, along with other problems, by Kerr (91). The smoothing of the 21-cm profiles has been discussed by Wilhelmsson and Winnberg (92). Central Region The kinematics of the gas near the center of the Galaxy was described by Rougoor (93) and by Oort (94). There is a 'nuclear disk', inside 8oo pc, rotating at about 200 km s-1 and there is no evidence that it is expanding. The velocity decreases abruptly within 100 pc from the nucleus. Most of the gas in the nuclear region is expanding with high velocities. The properties of the gas near the center of the Galaxy were considered by Lequeux (95) and Kerr (96). Expansion motions have been also found by observations of the OH radiation by Robinson et al. (97), Goldstein et al. (98) and Bolton et al. (99). High- Velocity Clouds The evidence for the existence of many high velocity clouds approaching the galactic plane from both hemispheres has been increasing in recent years. Such evidence has been collected by Oort (100, 101, 102, 103) and other astronomers in the Netherlands, such as Blaauw, Tolbert, Muller, Raimond, Schwarz, Hulsbosch and W. W. Shane (104, 105, 106, 107, 1o8). Most of these clouds, with velocities above 100 km s-1 , come from longitudes between 6o 0 and 200° (i.e. mostly between the direction of the anticenter and the direction of galactic

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rotation), and latitudes between + I0° and + 8o0 • The most probable explanation is that they are intergalactic in origin. Other possible explanations, e.g. that they are supernova shells, or remnants of a superexplosion, do not seem very probable. The flux of the incoming high-velocity hydrogen is of the order of 1019 atoms cm- 2 per million years; this corresponds to an increase of the mass of the disk by I o5 M® per million years. Perhaps the high velocity clouds could replenish the hydrogen of the nuclear part of our Galaxy. A different explanation for the high velocity clouds at latitudes below 25° was proposed by Habing (Io9), who considers them as belonging to an envelope of the Outer Arm. Shklovski (no), based on a suggestion by Varshalovitch, advanced the hypothesis that these clouds radiate only when they approach the galactic plane, because of a maser effect due to the excitation by Lyman-alpha radiation of hot stars. Dieter (In, 112) found many clouds with negative velocities of a few tens of km s-1 near the galactic poles. Smith (113) and Prata (I14) found clouds with positive radial velocities of the order of 100 km s-1, associated probably with the galactic structure. A search for OB stars near one of the high-velocity clouds is being made by Svolopoulos. BIBLIOGRAPHY

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Delhaye, J. 1965, Stars and Stellar Systems, 5, 61. Woolley, R. v. d. R. 1965, Stars and Stellar Systems, 5, 85. 1965, Stars and Stellar Systems, 5, III. Eggen, 0. J. Blanco, V. M. 1965, Stars and Stellar Systems, 5, 241. Plaut, L. 1965, Stars and Stellar Systems, 5, 267. Minkowski, R. 1965, Stars and Stellar Systems, 5, 321. Roman, N. G. 1965, Stars and Stellar Systems, 5, 345· Greenstein, J. L. 1965, Stars and Stellar Systems, 5, 361. 1965, Stars and Stellar Systems, 5, 393· Luyten, W. J. Arp, H. C. 1965, Stars and Stellar Systems, 5, 401. Munch, G. 1965, Stars and Stellar Systems, s, 203. Kerr, F.]., Westerhout, G. 1965, Stars and Stellar Systems, 5, 167. Blaauw, A. 1965, Stars and Stellar Systems, 5, 435· Bok, B.]. 1965, NATO Summer Course, 'Observational Aspects of Galactic Structure', Part 29, Athens. Perek, L. 1964, Pub!. astr. lnst. Czech. Ac. Sci., no. 48, Praha. Byrnes, D. V. 1966, Pub[. astr. Soc. Pacif., 78, 46. Boulon, J. 1963, c. r. Acad. Sci., Paris, 256, 5280. Boulon, J. 1963, J. Observateurs, 46, 225. Petrie, R. M. 1964, Mon. Not. R. astr. Soc., 128, 245· Howard, W. E. III, Kirk, J. G. Astr. J., 69, 544, 1964; 70,434, 1965. Fricke, W. 1966, Besans;on Colloquium, 'Nouvelles Methodes de Ia Dynamique Stellaire'. Wayman, P. A. 1966, Quart. J. R. astr. Soc., 7, 138; Observatory, 86, 185, 1966. Petrie, R. M. 1964, J. R. astr. Soc. Can., 58, 34· 1963, Mon. Not. R. astr. Soc., 125, 367. Feast, M. W. Feast, M. W., Shuttleworth, M. 1965, Mon. Not. R. astr. Soc., 130, 243. 1964, Astr. J., 69, 8o. Rubin, V. C., Burley, J. Barbier, M. 1966, J. Observateurs, 49, 269. 1963, Astrophys. J., 138, 1002. Abt, H. A., Bautz, L. P. Rubin, V. C. 1965, Astrophys. J., 142, 934· Bonneau, M. 1964, J. Observateurs, 47, 251. Munch, G., Miinch, L. 1964, Astrophys. J., I40, 162.

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I96S, Astrophys. J., 142, I64S· Feast, M. W., Thackeray, A. D. I966, Mem. R. astr. Soc., 70, 33· Thackeray, A. D. I96s, Trudy astrofiz. lnst. Alma-Ata, 5, 224. Mirzoyan, L. V., Kazarian, E. S. I964, Publ. R. Obs. Edinburgh, 4, 87. Stibbs, D. W. N. J. Observateurs, 48. II9, I96s; Thesis, Bull. Inst. Statist. Univ. Paris, Massonie, J.P. l.f0 I, I 9 6s. I96S, NATO Summer Course 'Kinematic and Chemical History of the 37· Eggen, 0. J. Galaxy', Herstmonceux. I966, Astr. J., 71, 40I. 38. van Wijk, V., Smith, B. F., Daniels, W. E. I963, Bull. astr. Inst. Csl., 14, 2I8. 39· Perek, L. I964, Publ. astr. Soc. Pacij., 76, I97· 40. Minkowski, R. I966, Mon. Not. R. astr. Soc., 132, 49S· 41. Feast, M. W. I966, Publ. astr. Soc. Pacij., 78, 39· 42• Schlesinger, B. M. I96S, Publ. astr. Soc. Japan, 17, 7I. 43· Takayanagi, K. I96S, Trudy astrofiz. Inst. Alma-Ata, 5, 69. 44· Pavlovskaya, E. D. I964, Publ. astr. Soc. Pacif., 76, 403. 45· Dahn, C. C. I966, Acta Astr. 16, 33S· 46. Rudnicki, K. I967, R. Obs. Bull. (in press) . 47· Murray, C. A. I96S, Astrophys. J., 142, 943· .fS. Smak, J. 1., Preston, G. W. I96S, R. Obs. Bull., 49· Woolley, R. v. d. R., Harding, G. A., Cassells, A. 1., Saunders, J. no. 97· I966, R. Obs. Bull., no. II4. 50. Woolley, R. v. d. R., Aly, K. I967, R. Obs. Bull. (in press). 51. Clube, S. V. M. sa. van Herk, G. I96s, Bull. astr. Inst. Netherlds, 18, 7I. Tartu Astr. Obs. Publ., 34, 47, I964; 34, I2I, I964; 35, 49, 53· Eelsalu, H., Joeveer, M. I966. Astr. Zu., ;p, I6o, S8I, I96S = Sov. Astr., 91 124, 46I, I966. 54· Shatsova, R. B. I966, Astr. J., 71, 64. 55· King, I. I966, Besan~on Colloquium, 'Nouvelles Methodes de la Dynamique 56. Bouvier, P. Stellaire'. I96s, Trudy astrofiz. Inst. Alma-Ata, 5, 233· 57· Dzigvashvili, R. M. I963, Mon. Not. R. astr. Soc., u6, 38I. 58. Kennedy, P. M., Przybylski, A. I96S, Izv. Krym. astrofiz. Obs., 59· Vitrichenko, E. A., Gershberg, R. E., Metik, L. P. 34. I93· I96S, Konikl. Nederl. Akad. Wetenschappen, Verslagen Afd. Natuurkunde, 6o. Blaauw, A. 74, no. 4· I967, R. Obs. Bull. (in press). 61. Clube, S. V. M. 1966, Bull. astr., 3e Ser., x, 87. 6z. Mouchet, M. T. I966, Bull. astr., 3e Ser., x, 95· 63. Martinet, L. I963, C. R. Acad. Sci., Paris, :1157, 2965, 33os. 64. Nahon, F. I96S, Ann. Sci. Univ. Besanfon, 3e Ser., Fasc. 4· 65. Massonie, J.P. I966, C. R. Acad. Sci., Paris, z62, 59I, 673. 66. Massonie, J.P. I964, Astronomie, 78, 437· 67. Cayrel, R., Kovalevsky, J. I96S, NATO Summer Course 'Observational Aspects of Galactic Structure', 68. Cayrel, R. Parts 2S, 26, Athens. I963, Astr. J., 68, 697. 69. Eggen, 0. J. I964, Astr. J., 69, s7o. 70. Eggen, 0. J. I964, Astrophys. Norv., 9, 333· 71. Stromgren, B. I966, Bull. astr. lnst. Netherlds, 18, ISO. 72. Oosterhoff, P. T., Ponsen, I. I964, Ann. Astrophys., 27, 672. 73· Kreiken, E. A., Yilmaz, N. I966, Astrophys. J., 146, s8I. 73a. Dennis, T. R. I96S, Bull. Acad. Pol. Sci., Ser. Sc. Math. Astr. Phys., 74· lwanowska, W., Kanthak, J. 13, ISS· Bull. Acad. Pol. Sci., Ser. Sc. Math. Astr. Phys., 13, 75· lwanowska, W., Boenigk, T. 163, I96S; IJ, I69, I96S. 196s, Bull. Acad. Pol. Sci., Ser. Sc. Math. Astr. Phys., 13, I7S· 76. Boenigk, T.

32. 33· 34· 35· a6.

708 77· 78. 79· So. SI. 82. SJ. S4. S5.

86. S7.

SS. S9. 90. 9I. 92. 93· 94· 95·

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97· 9S. 99· Ioo. IOI. I02. IOJ. I04. I05. I06. I07. Io8. I09. no. III. II2. IIJ. II4·

COMMISSION 33 1964, Z. Astrophys., 5S, 217. Schmidt-Kaler, T. 1965, Astr. J., 70, 147. Schmidt-Kaler, T. 1964, Mem. Coll. Sci., Univ. Kyoto, A 30, no. 3, 333· Shimizu, T., Takahashi, K. 1966, Bull. astr. lnst. Netherlds, IS, 263. Shane, W. W., Bieger-Smith, G. P. 1966, Bull. astr. lnst. Netherlds, IS, 247. Burton, W. B. 1964, IAU-URSI Symposium no. 20, Canberra. Kerr, F.]. 1963, Bull. astr. lnst. Netherlds, I7, 132. Braes, L. L. E. 1965, NATO Summer Course 'Kinematic and Chemical History of Shane, W. W. the Galaxy', Herstmonceux. 1966, Astrophys. J., IJ9, 1066. Locke, J. L., Galt, J. A., Costain, C. H. 1965, Bull. Obs. Tonantzintla y Tacubaya, 4, 8. Pismis, P. 1966, Besan~on Colloquium, 'Nouvelles Methodes de la Dynamique Dixon, E. Stellaire'. Astr. Zu., 4I, 1027, 1964 = Sov. Agekyan, T. A., Petrovskaya, I. V., Fesenko, B. I. Astr., S, 823, 1965; Astrophysika, I, 373, 1965. Astr. Zu., 42, 923, 1965 = Sov. Astr., 9 1 709, 1966. Pronik, I. I. 1966, Bull. astr. lnst. Netherlds, Suppl., I, 77, 177. Lindblad, P. 0. 1965, NATO Summer Course 'Observational Aspects of Galactic Structure', Kerr, F.]. Parts 25, 26, Athens. 1963, Astr. Notes, Univ. Gothenburg, no. 8, 20. Wilhelmsson, H., Winnberg, A. 1964, Bull. astr. lnst. Netherlds, I71 381. Rougoor, G. W. 1966, IAU-URSI Symposium No. 31, Noordwijk. Oort, J. H. 1966, IAU-URSI Symposium No. 31, Noordwijk. Lequeux, J. 1965, NATO Summer Course 'Kinematic and Chemical History of the Kerr, F. J. Galaxy', Herstmonceux. 1964, Nature, Robinson, B. J., Gardner, F. F., van Damme, K. ]., Bolton, ]. G. 202, 989. 1964, Nature, Goldstein, S. ]., Jr., Gundermann, E. ]., Penzias, A. A., Lilley, A. E. 203, 65. 1964, Nature, 204, 30. Bolton, J. G., Gardner, F. F., McGee, P. X., Robinson, B. ]. 1966, Trans. IAU, I2 B, 395, 789. Oort, J. H. 1966, Bull. astr. lnst. Netherlds, IS, 421. Oort, J. H. 1966, IAU-URSI Symposium No. 31, Noordwijk. Oort, J. H. 1966, Ventlesen Award Lecture, Columbia University. Oort, J. H. 1966, IAU-URSI Symposium No. 31, Noordwijk. Blaauw, A. 1966, Bull. astr. lnst. Netherlds, IS, 405. Blaauw, A., Tolbert, C. R. 1966, Bull. astr. Inst. Muller, C. A., Raimond, E., Schwarz, U. 1., Tolbert, C. R. Netherlds, Suppl. I, 215. 1966, Bull. astr. lnst. Netherlds, IS, 413. Hulsbosch, A. N. M., Raimond, E. 1966, IAU-URSI Symposium no. 31, Noordwijk. Shane, W. W. 1966, Bull. astr. lnst. Netherlds, IS, 323. Habing, H.]. 1966, IAU-URSI Symposium no. 31, Noordwijk. Shklovski, I. S. 1964, Astr. J., 69, 288. Dieter, N. H. 1965, Astr. J., 70, 552. Dieter, N. H. 1963, Bull. astr. lnst. Netherlds, I7, 203. Smith, G. P. 1964, Bull. astr. lnst. Netherlds, I7, 511. Prata, S. W. X. DYNAMICS

(prepared by G. Contopoulos) Oort's (I) chapter on Stellar Dynamics in Stars and Stellar Systems, Vol. 5, gives an account of the progress made in many traditional problems of Stellar Dynamics, emphasizing their relations to observation. At the same time, a number of new developments in Stellar Dynamics should be noted.

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(a) An approach between Stellar Dynamics and Celestial Mechanics, as indicated by the IAU Symposium no. 25 in Thessaloniki (the Proceedings have been edited by Contopoulos (z) ). The same trend was evident at the Besan~on Colloquium in I966 (Bull. astr., Paris, 3eme serie, Z, fasc. I, I967). (b) The use of experimental methods in Stellar Dynamics, with the help of fast electronic computers; (c) The development of new statistical methods; in particular the use of methods developed in plasma physics; (d) The development of new gravitational theories concerning the formation of galactic structure. The Gas Dynamical Problems and the Magnetic Fields of our Galaxy have been discussed by Woltjer (3). Three earlier review articles connected with Galactic Dynamics should be mentioned: the first, by King (4), refers to the Dynamics of Galaxies in general; the second, by Wentzel (5), refers to the Magnetic Fields and Spiral Structure; and the third article, by Contopoulos (6), deals with problems of Stellar Dynamics in general. Other discussions of problems of Stellar Dynamics, and Galactic Dynamics in particular, were given by Oort (7), Prendergast (8) and Kuzmin (9). The connection between Stellar Dynamics and Celestial Mechanics was discussed by Kovalevsky (10). A book on Stellar Dynamics by Ogorodnikov (11) appeared in English translation. Stellar Orbits- Third Integral Two review articles on the theory of orbits in the Galaxy have been written by Ollongren (12, 13)· Contopoulos and Stromgren (14) have calculated numerically tables of plane galactic orbits, with the aim of finding the places of formation of stars with ages of a few times Io8 years. Recent application to a sample of stars indicates that the stars of this age range originated either in the Orion or in the Perseus arm; one can even find the general areas where star formation has been most active. The perturbations of the orbits, due to the spiral arms, have been considered by Barbanis and by Lin, and they were found to be small in general. An epicyclic theory for orbits in a spiral field has been developed by Woltjer and Barbanis. Plane orbits in particular models of the Galaxy were studied by Woolley (15), Perek (16) and Genkin (17). Takayanagi (18) calculated plane orbits of subdwarfs. He found a concentration of perigalactic distances between I •5-3•0 kpc; this indicates that the subdwarfs originated in the central bulge. Orbits in special fields have been considered by Nahon (19) and Losco (zo). Three-dimensional orbits in particular galactic models were studied theoretically by Perek (z1) and numerically, with limited accuracy, by Innanen (z:z). Woolley (23, 24) continued his work on the galactic orbits of nearby stars and globular clusters. The statistics and dynamics of the orbits of globular clusters in the Galaxy have been studied by Henry-Hillaire, and by Ogorodnikov (25). Matsunami (z6) found correlations between various characteristics of the orbits of globular clusters and their physical properties. Orbits of n gravitating bodies have been calculated numerically by a number of authors such as Sherman and Kinman (27), Aarseth (28), Wielen (29) and Standish and Szebehely, in order to study the evolution of n-body systems.

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The problem of the accuracy of the n-body problem calculations and the related problem of the reversibility in stellar dynamical systems was considered by Miller (30). Hayli (31) began n-body problem calculations taking into account also the external galactic field. Lindblad (32) continued his work on the evolution of a system of massive bodies (cloud complexes) in the galactic field. Van Albada (33, 34) and Worall (35) studied the evolution of many small stellar systems; they found that in most cases their final state is only a double star. Collisionless orbit calculations were made by Aarseth (36) for n = 1000. Some insight into the n-body problem can be achieved by one-dimensional calculations, as done by Lecar (37) and by Hohl and Feix (38). One can investigate in this way whether or not there is a tendency to an equilibrium and the nature of this equilibrium, also the breaking up of the system into subsystems, etc. Of interest are some calculations of the evolution of collapsing collisionless systems by Henon (39, 40) and Campbell (41), by means of orbit calculations, as well as a few calculations of the acceleration of the rate of collisions at the center of very dense systems by Ulam and Walden (42). A short discussion of then-body problem from the numerical point of view has been given by Aarseth and Hoyle (43). An IAU Colloquium on the gravitational n-body problem is scheduled for the summer of 1967 in Paris. Orbit calculations in connection with the existence of a 'third' integral of motion were made by many authors. Henon and Heiles (44) have studied the intersections of many orbits by a surface of section in a simple dynamical problem of two degrees of freedom. They found indications for the existence of an isolating or very nearly isolating 'third' integral of motion for small energies, while for large energies the 'third' integral tends to become ergodic. Similar results were reported by Perek and Peterson and by Ollongren at the Thessaloniki 1964 Symposium. Hayli (45) and Aarseth (46) found similar results for high velocity orbits of our Galaxy, e.g. orbits of globular clusters, especially if these orbits pass through the central region of the Galaxy. It seems, however, that a third integral is nearly isolating when the velocities on a meridian plane do not exceed a few hundred km s-1• Barbanis (47) found empirically a third integral, which persists even when the energy exceeds the energy of escape, and which keeps some stars from escaping to infinity. A classification of the integrals of motion into isolating, quasi-isolating and ergodic has been given by Contopoulos (48). The third integral in a non-smooth potential has been studied by Contopoulos and Woltjer (49). Other special cases of the third integral have been studied by Andrle (so). Tables of the coefficients of the third integral in a special case have been prepared by Contopoulos (51). Contopoulos and Moutsoulas (52, 53) have studied the resonance cases and the effects of the small divisors in the third integral. The resonance effects were used by Contopoulos (54) to explain the tube orbits (i.e. elongated orbits near periodic orbits), that were found by Ollongren (12, 13) and others in our Galaxy. Further work on the integrals of stellar motion has been done by Barbanis (55), Schmeidler (56), Kuzmin (57), Idlis (58), Ogorodnikov (59), Message (6o), and Nahon (61). Gustavson (62) found a good agreement between a theoretical form of the third integral and the numerical results of Henon and Heiles. A comparison of theoretical and experimental results was made also by Roels (63). Hori and Liu (64) used a third integral in the theory of the velocity ellipsoid. Recent developments in the theory of the third integral include numerical and theoretical results on the restricted three-body problem by Deprit, Henon, Bozis and Contopoulos; the theories of satellite orbits around an oblate planet by Vinti, Conley, Kyner, etc., and many papers on non-linear mechanics with applications to various problems of mathematics,

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physics, chemistry, engineering and astronomy. In particular, the study of adiabatic invariants and experimental results in plasma physics and geophysics, as in the case of mirror machines and the van Allen belts, have much similarity with the astronomical problems mentioned above. No detailed reference will be made to these papers, however. The theoretical problem of the existence of integral surfaces in non-integrable systems of two degrees of freedom has been solved by Arnol'd and by Moser. Arnol'd (65) has written a number of papers on this problem and related problems in recent years. Moser has proved recently that the motions near a periodic orbit or an equilibrium point are quasi-periodic for a set of initial conditions of positive measure. The corresponding expansions of the form of the third integral or the von Zeipel method are convergent. These theorems have been applied to various problems by Moser and Jefferys (66, &]). A similar theorem has been proved in a special case by Barrar (68). These theorems, however, are proved only for a very small neighborhood of the periodic orbit or the equilibrium point. In order to study how far the third integral is applicable, numerical methods are necessary. Contopoulos (69) found that the breakdown of the third integral for large perturbations is due to a concentration of resonance regions; thus a numerical estimate of the breakdown perturbation can be found. Models of the Galaxy

A number of mass-models of the Galaxy have been proposed recently. A simple formula for the force and potential on the plane of symmetry of the Galaxy has been used by Contopoulos and Stromgren (14). Besides the well known new Schmidt (7o) model, Innanen (71) constructed a number of galactic models, consisting of concentric spheroids, and studied their properties. Kuzmin and Kutuzov (72, 73) have also considered various models of the Galaxy. Genkin (74, 75) has studied models admitting an exact third entegral of motion. Further models have been constructed by Einasto and Kutuzov. Self-gravitating models of galaxies, satisfying Liouville's and Poisson's equations have been given by Prendergast, Vandervoort (76), Aoki (77) and Perek (78). A self-gravitating model for a flat galaxy with a truncated Schwarzschild distribution of velocities has been given by Ng. Toomre (xo6), Hunter (xo8), and Barbanis and Prendergast have developed methods of finding the potential corresponding to a given density of a flat disk and vice-versa. Wallace and Copeland (79) have studied the velocity field in a particular model of a spiral galaxy. The flux of the angular momentum in a spiral galaxy was considered by Starr and Newell (So). The distribution of mass and angular momentum in our Galaxy has been studied by Takase (81). Hodge (82) found limits of the mass of our Galaxy between 1·5 x 1o11M® and 6 x 1o11M®. Data about the galactic field have been derived by King from a study of the boundaries of globular clusters. Kreiken (83) proposed a set of galactic constants R 0, 8 0 , A and B, derived from his polytropic galactic model. The force perpendicular to the galactic plane has been studied by Stothers and Tech (84) through the kinematics of OB stars. Dorchner, Gurtler and Schmidt (85) derived, from the magnitude of this force, the density of molecular hydrogen near the Sun; they found that 8o% of the hydrogen is in molecular form. Belton and Brandt (86) succeeded in reproducing the rotation curve of our Galaxy by assuming that it consists of a set of spheroidal homoeoids; they concluded that the distribution of the 'missing matter' is like halo population II objects. Various assumptions about the distribution of the 'missing matter' were discussed by Oort (1, 7). o2

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Woolley found, through a study of the z-velocities of faint Ao stars, that the total density in the solar neighborhood is smaller than the accepted value; thus the amount of 'missing matter' is less than previously assumed. Similar results were found by Einasto (87). The mass of the galactic nucleus was estimated recently by Lequeux (88) to be of the order of 1o8M®. Rougoor (89) estimated the mass of the neutral atomic hydrogen in the central disk to be 3 x 1o6M®. Statistical Methods- Stability Problems

Lynden-Bell (90, 91) has developed a new statistics, similar to the Fermi-Dirac statistics, to describe the properties of a collapsing galaxy. A numerical example presented by Henon at the Besans;on Colloquium shows partial agreement with this theory. A statistical theory of the gravitational forces in a stellar field has been given by Camm (92). A Monte-Carlo method to deal with encounters in the n-body problem, was developed by Henon (93, 94). This method appears very promising for obtaining quickly results on the evolution of stellar systems. Massonie (95) began the study of a markovian process that changes progressively the velocity distribution in a stellar system. Plasma dynamics has initiated the development of new methods in stellar dynamics in recent years. Prigogine and Seveme (C)6, 97) have developed statistical mechanical methods to deal with the gravitational n-body problem. They introduced non-markovian equations to take account of the 'memory' of previous conditions. The n-body system does not tend to an equilibrium state, but its final evolution depends on the initial conditions. Application of the methods of plasma physics to stellar systems has been made by Lebedev, Maksumov and Marochnik (98, 99, 100). In particular they considered the growth of instabilities on a time scale of a few times 108 years. On the other hand Antonov has shown that a one-dimensional stellar system is stable. A general discussion of cooperative phenomena in stellar dynamics has been made by Lynden-Bell (101). He discussed, among other subjects, a necessary and sufficient condition, due originally to Antonov (102), for the stability of a stellar gas. Further Lynden-Bell continued Antonov's discussion of the entropy in stellar systems. Gravitational instability plays a role in the formation of galaxies, of large scale structures of galaxies, and of stars. Only work connected with the second problem will be mentioned here. The influence of rotation on the gravitational instability of a cloud has been considered by Amy (103) and by Simon (104). A number of authors have discussed the stability of a disk of stars or gas against axisymmetric perturbations. Toomre (105) found that a velocity dispersion is needed to stabilize the galactic disk. The minimum velocity dispersion required for stability near the Sun is between 20 and 35 km s-1 • Non linear effects and other generalizations were given by Graham (107). Hunter (1o8) has studied free modes of oscillation in the plane of infinitesimally thin disks with no velocity dispersion. The effect of the z-dimension on the stability of a disk of finite thickness was studied by Sweet and McGregor (109, no). The stability of a rotating disk of gas has been considered by Goldreich and Lynden-Bell (111). Lynden-Bell (112) has studied the large-scale instabilities of Maclaurin spheroids during collapse.

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Owaki (113) has studied the stability of an incompressible galactic nucleus under the influence of the galactic disk. Ostriker (114) has studied the stability of self-gravitating rings and cylinders. Non-axi-symmetric instabilities of a generally spiral form are mentioned below. There is a series of papers in the Astrophysical Journal on rotating gaseous masses by Chandrasekhar, Lebovitz, Roberts, Hurley and Limber. These papers, however, are rather loosely connected with our problems. Dynamics of Spiral Structure

Lin (115, 116) has emphasized the fact that the magnetic field of the Galaxy is quite insufficient to explain the main spiral effects of our Galaxy. On the other hand the winding difficulty of differentially rotating spiral arms is well known. Thus Lin developed a spiral pattern theory, of the type proposed originally by B. Lindblad, assuming that the stars move freely through the spiral pattern, which is a density wave rotating like a rigid body. Lin and Shu (115, u6, 117, n8) have found the response of gas and stars to an imposed rotating spiral field. A possible spiral solution is found when the induced field is equal to the imposed one. This method gives preference to trailing arms. The effect of a finite thickness of the Galaxy has been considered by Shu. A similar theory, which includes also non-linear effects and boundary conditions, was developed by Kalnajs (119). A paper by the late B. Lindblad (uo) describes his own views on the circulation of matter in a spiral galaxy. The angular velocity of the spiral pattern was determined to be about 20 km s-1 kpc-1 by Stromgren, who compared the present position of the Perseus arm with its position when stars with ages of a few times 108 years were formed. Julian and Toomre (121) have developed a local theory for the formation of trailing spiral structures in differentially rotating stellar disks due to concentrated perturbations. If the perturbation is permanent, e.g. a point mass, the mass of the resulting trailing arms can be larger, by an order of magnitude, than the perturbing mass. If, however, the forcing is temporary, then the resulting spiral response is also temporary. Rehm (122) found, under various conditions, both trailing and leading spiral patterns. The problem of a gaseous disk was considered in detail by Goldreich and Lynden-Bell (uJ, 124) who found trailing (sheared) instabilities. These instabilities are transient, but they are regenerated continuously. Similar views were developed by Toomre. Reviews of spiral structure theories were given by Lynden-Bell (us) and Prendergast (u6). Spiral instabilities in special cases were considered by Buggish and Kahn (127) and by Helfer (uS). Contopoulos (129) found a new integral of motion in a disk spiral galaxy. Barbanis found numerical evidence from orbit calculations for the existence of such an integral in most cases of actual interest. Such an integral may be useful for the construction of spiral models of the Galaxy. Some n-body problem calculations are connected with the formation or evolution of spiral structures. Such work has been done by Lindblad (32). Prendergast, as well as Contopoulos and Barbanis, are studying the evolution of a plane galaxy by calculating a very large number of orbits. A theory of galactic structure based on the accretion of interstellar matter has been developed by Lyttleton and Bondi (130).

714

COMMISSION 33 Magnetic Fields- Dynamics of Central Region

Lynden-Bell (131, 132) has found that a magnetic field can initiate spiral instabilities in a galaxy. Freeman and Mestel (133) indicated the difficulties of constructing a model, in which magnetic forces maintain a differentially rotating spiral pattern. Pacholczyk (134) and Stodolkiewicz (135) have studied the stability of the whole Galaxy and, in particular, spiral arms, taking into account both magnetic and gravitational effects. Similar work for the spiral arms was done by R. Graham (136). A theory of the formation of galactic spiral structure through the contraction of metagalactic gas possessing a magnetic field has been developed by Pikel'ner (137). Fujimoto (138) proposed a mechanism to explain the expansion of the 3 kpc arm. He assumed that circular orbits are unstable in this region and an inflow of gas from the halo takes place there. The expansion is produced by a coupling of differential rotation and the magnetic field. Oki, Fujimoto and Hitotuyanagi (139) have developed a theory combining gravitational and magnetic effects in the formation of spiral arms. In addition, Fujimoto (140) has considered the formation of dark lanes in a galaxy by non-circular motions of gas. Setti (141) found indications that the gravitational field of a spiral arm stabilizes it when the magnetic field is helical. Arguments for the existence of a helical field were given by Hornby (142). A model of a helical field with inclined windings has been considered by Stepien (143). Greyber (144) supported the view that the magnetic field above the galactic plane is opposite in direction to that below. An attempt to consider the dynamics of a galactic plasma by using an ellipsoidal distribution law of velocities was made by Pratap (145). Sakakibara (146) has studied the diffusion of the cosmic rays due to the magnetic field of the Orion arm, which results in an anisotropy of the cosmic ray flux. Various determinations of the magnetic field in our Galaxy have been reviewed critically by Woltjer (3, 147). The arguments for a strong field in the spiral arms, of the order of 3 x 10-5 gauss, arise from observations of synchrotron radiation, and considerations about the Faraday rotation, the alignment of dust grains and the solar wind. Arguments for a weak field of a few times 10-6 gauss, are based on the absence of a measurable Zeeman effect and considerations about star formation. The field in the halo seems to be of the order of a few times 10-6 gauss. A recent review of the situation was given by van de Hulst (148). Mathewson and Milne have found a spiral pattern by radio studies of the Faraday rotation. Brouw has determined the magnetic field in the galactic spurs. The magnetic field in filamentary structures was studied by Pronik, who confirmed previous conclusions by Shajn. A number of papers on the magnetic fields of our Galaxy by Jacklyn, Gardner, Whiteoak, Piddington, and Visvanathan were presented at the Mount-Stromlo 'Pre-Symposium' on 'Radio and Optical Studies of the Galaxy', in May 1966. In some cases the field may be very strong, of the order of Io- 3 gauss; such indications were found by Davies, de Jager and Verschuur (149) by studying the polarization of OH sources. The magnetic field near the center of the Galaxy was estimated by Downes and Maxwell (150) to be between 5 x Io-5 and 5 x 10-4 gauss. It is not clear how magnetic effects could explain the expansion motions near the center of the Galaxy.

STRUCTURE DU SYSTEME GALACTIQUE

715

An explanation based on an explosion of the galactic nucleus was proposed by G. Burbidge and Hoyle (ISI), Lequeux (I52), and Ishida (ISJ). Further support of this view was provided at the IAU Symposium no. 31, in Noordwijk. Pikel'ner (I54) suggested that the energy needed for the activity of the central region comes from the gravitational contraction of gas clouds. The phenomena occurring during stellar collisions at the center of the Galaxy have been considered by Spitzer and Saslaw (ISS)· Lequeux (I52) and Ginzburg and Syrovatskii {IS6) suggested that most of the cosmic rays come from the explosion of the galactic nucleus. This subject has also been studied by Rosen {I57)· Miscellaneous Problems

Mestel {ISS) has studied the evolution of a rotating spherical cloud into a thin disk. Depending upon the initial density distribution the final result is a spiral or a barred spiral. Lin, Mestel and Shu {IS9) have studied the collapse of a uniform spheroid. Crzedrielski (I6o) has considered the fragmentation of a galaxy during collapse. Milder (I6I) has considered the flattening of a rotating isothermal model. A virial theorem for a continuous distribution of mass has been given by Camm (I62). King ( I63) has given a relation between velocity distributions and spatial gradients in a stellar system. He found the ratio of the axes of the velocity ellipsoid from moment equations. The problem of the deviation of the vertex has been considered by Genkin (I64). Kuzmin (I6S) has considered the conditions for the existence of a plane of symmetry in stellar systems. Kitamura (I66) has studied the effect of the encounters on a stellar velocity spheroid; in a time of the order of the time of relaxation, the velocity dispersions become appreciably smaller and approach each other. Lynden-Bell (I67) has considered the problem of the bending of the galactic plane. He attributed it to a r o deviation between the galactic axis of symmetry and its angular momentum. The same effect was attributed to the action of the Magellanic Clouds by Avner {I68). Toomre and Hunter have studied this problem from the point of view of the stability of a disk towards bending. Some bending modes are excited by the Magellanic Clouds. BIBLIOGRAPHY I. 2.

3· 4·

S· 6. 7· 8. 9· IO. II.

I2. I3.

Oort, ]. H. 1965, in Stars and Stellar Systems, 5, 455· Contopoulos, G. (ed.) 1966, The Theory of Orbits in the Solar System and in Stellar Systems, IAU Symposium No. 25, Academic Press. Woltjer, L. 1965, in Stars and Stellar Systems, 5, 531. King, I. 1963, A. Rev. Astr. Astrophys., I, 179. Wentzel, D. G. 1963, A. Rev. Astr. Astrophys., I, 195. Contopoulos, G. 1966, Problems of Stellar Dynamics, Proc. Space Math. Seminar, I, 169, American Mathematical Society. Oort, J, 1965, NATO Summer Course 'Observational Aspects of Galactic Structure', Part 23, Athens. 1966, IAU-URSI Symposium no. 31, Noordwijk. Prendergast, K. 1965, Trudy astrofiz. lnst. Alma-Ata, 5, II, 70. Kuzmin, G. G. 1966, Besan~on Colloquium 'Nouvelles Methodes de la Dynamique Kovalevsky, J. Stellaire'. Ogorodnikov, K. F. 1965, Dynamics of Stellar Systems, Pergamon Press. Ollongren, A. 1965, A. Rev. Astr. Astrophys., 3, II3. Ollongren, A. 1965, in Stars and Stellar Systems, 5, 501.

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14. Contopoulos, G., Stromgren, B. I965, Tables of Plane Galactic Orbits, Inst. Space Studies, New York. 15. Woolley, R. v. d. R. I964, Astrophys. Norv., 9, 26I. 16. Perek, L. I964, Vistas in Astronomy, 5, 28. 17. Genkin, I. L. I966, Trudy astrofiz. Inst. Alma-Ata, 7, I6. 18. Takayanagi, K. I965, Publ. astr. Soc. Japan, 17, 7I. 19. Nahon, F. I966, Besan~on Colloquium 'Nouvelles Methodes de Ia Dynamique Stellaire'. :zo. Losco, L. I966, Besan~on Colloquium 'Nouvelles Methodes de la Dynamique Stellaire'. :n. Perek, L. I966, Bull. astr. Inst. Csl., 17, III. 22. Innanen, K. A. 1966, Z. Astrophys., 64, 445, 457· 23. Woolley, R. v. d. R. I965, NATO, Summer Course 'Kinematical and Chemical History of the Galaxy', Herstmonceux. 24. Woolley, R. v. d. R. I967, R. Obs. Bull. (in press). 25. Ogorodnikov, K. F. 1965, Trudy astrofiz. Inst. Alma-Ata, 5, 2I9. 26. Matsunami, N. 1964, Publ. astr. Soc. Japan, 16, I41. 27. Sherman, N. W., Kinman, D. 1964, Astr. J., 69, 149· :z8. Aarseth, S. J. Mon. Not. R. astr. Soc., 126, 223, 1963; 132, 35, 1966. 29. Wielen, R. 1966, Besan~on Colloquium 'Nouvelles Methodes de Ia Dynamique Stellaire'. JO. Miller, R. H. 1964, Astrophys. J., 140, 250. JI. Hayli, A. 1966, Besan~on Colloquium 'Nouvelles Methodes de Ia Dynamique Stellaire'. 32. Lindblad, P. 0. I966, Besan~on Colloquium 'Nouvelles Methodes de Ia Dynamique Stellaire'. 33· van Albada, T. S. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. 34· van Albada, T. S. 1966, Besan~on Colloquium 'Nouvelles Methodes de Ia Dynamique Stellaire'. 35· Worall, G. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. 36. Aarseth, S. ]. 1966, Besan~on Colloquium 'Nouvelles Methodes de Ia Dynamique Stellaire'. 37· Lecar, M. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. 38. Hohl, F., Feix, M. R. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. 39· Henon, M. 1964, Ann. Astrophys., 27, 83. 40. Henon, M. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. 41. Campbell, P.M. I966, Proc. nat. Acad. Sci., 55, I. 42· Ulam, S. M., Walden, W. E. 1964, Nature, 201, I202. 43· Aarseth, S. J., Hoyle, F. 1964, Astrophys. Norv., 9, 3I3. 44· Henon, M., Heiles, C. I964, Astr. J., 6g, 73· 45· Hayli, A. 1965, Ann. Astrophys., 28, 49· 46. Aarseth, S. J. 1966, Nature, 212, 57· 47· Barbanis, B. I966, Astr. J., 71, 4I5. 48. Contopoulos, G. 1963, Astrophys. J., 138, 1297· 49· Contopoulos, G., Woltjer, L. I964, Astrophys. J., 140, no6. so. Andrle, P. 1966, Bull. astr. Inst. Csl., 17, 166, 169. 51. Contopoulos, G. 1966, Astrophys. J, Suppl., IJ, 503. 52. Contopoulos, G. 1963, Astr. J., 68, 763. 53· Contopoulos, G., Moutsoulas, M. Astr. J., 70, 817, I966; 71, 687, 1966. 54· Contopoulos, G. 1965, Astr. J., 70, 526. 55· Barbanis, B. 1965, Astr. J., 70, 285.

STRUCTURE DU SYSTEME GALACTIQUE s6. 57· 58. 59· 6o. 61. 62. 63. 64. 65. 66.

67.

68. 69. 70. 71. 72. 73· 14· 75· 76. 77· 78. 79· So. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93· 94· 95· g6.

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Schmeidler, F. 1963, Astr. Nachr., 287, I. Kuzmin, G. G. 1964, Tartu astr. Obs. Publ., 34, 457· 1965, Trudy astrofiz. Inst. Alma-Ata, 5, IO!). Idlis, G. M. Ogorodnikov, K. F. 1965, Trudy astr. Obs. Leningrad. Univ., 22, 132. 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Message, J. P. Stellaire'. Nahon, F. 1966, C. R. Acad. Sci., Paris, 262, 669. 1966, Astr. J., 71. Gustavson, F. G. Roels, J, 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Stellaire'. Hori, G., Liu, T. 1963, Publ. astr. Soc. Japan, 15, roo. Arnol'd V. I. Uspekhi Mat. Nauk, 18, no. 5 (II3), 13, 1963; 18, no. 6 (II4), 91, 1963; Sov. Math. Dokl., 161, 331, 1965. Jefferys, W. H. 1966, Astr. J., 71, 306. Moser, J ., Jefferys, W. H. 1966, Astr. J., 71, 568. Barrar, R. 1966, Amer. J. Math., 88, 206. 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Contopoulos, G. Stellaire'. 1965, in Stars and Stellar Systems, 5, 513. Schmidt, M. Innanen, K. A. Astrophys. J., 143. ISO, I 53. 1966; z. Astrophys., 64, I 58, 1966. Kuzmin, G. G. 1966, Tartu astr. Obs. Publ., 35, 285. Kuzmin, G. G., Kutuzov, S. A. 1966, Tartu astr. Obs. Publ., 35, 316. Genkin, I. L. 1963, SoobSc. gos astr. Inst. Sternberg, no. 129. Genkin, I. L. 1966, Trudy astrofiz. Inst. Alma-Ata, 7, r6. 1966, 14th Liege Symposium, Gravitational Instability and the Vandervoort, P. 0. Formation of Stars and Galactic Structures. Aoki, S. 1965, Publ. astr. Soc. Japan, 17, 273. Perek, C. 1966, Bull. astr. Inst. Csl., 17, 333· Wallace, J. M., Copeland, J. A. 1964, Publ. astr. Soc. Pacij., 76, 315. Starr, V. P., Newell, R. E. 1963, Publ. astr. Soc. Pacif., 75, 239. Takase, B. 1966, Publ. astr. Soc. Japan (in press). 1966, Proc. astr. Soc. Pacif., 78, 72. Hodge, P. W. Kreiken, E. A. 1964, Observatory, 84, II5. Stothers, R., Tech, J. L. 1964, Mon. Not. R. astr. Soc., 127, 287. 1964, Astr. Nachr., 288, 149· Dorschner, J., Gurtler, J., Schmidt, K. H. 1963, Ann. Astrophys., 26, 229. Belton, M. J. S., Brandt, J. C. Einasto, J. 1964, Comm. Tartu astr. Obs., no. II, 1. Lequeux, J. 1966, IAU-URSI Symposium no. 31, Noordwijk. 1966, IAU-URSI Symposium no. 31, Noordwijk. Rougoor, G. W. 1966, 14th Liege Symposium, Gravitational Instability and the Lynden-Bell, D. Formation of Stars and Galactic Structures. Lynden-Bell, D. 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Stellaire'. 1963, Mon. Not. R. astr. Soc., 126, 283. Camm, G. L. 1966, C. R. Acad. Sci., Paris, 262, 666. Henon, M. 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Henon, M. Stellaire'. 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Massonie, J. P. Stellaire'. Prigogine, I., Severne, G. 1966, Physica (in press). 1966, Besanr;on Colloquium 'Nouvelles Methodes de la Dynamique Severne, G. Stellaire'. Marochnik, L. S. Astr. Zu., 41, 264, 1964 = Sov. Astr., 8, 202, 1964; Astr. Zu., 43, 560, 919, 1966. Lebedev, V. I., Maksumov, M. N., Marochnik, L. S. Astr. Zu., 42, 709, 1965 = Sov. Astr., 9, 549, 1966.

718

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Astr. Zu., ..p, 1261, 1965 = Sov. Astr., 9, 100. Maskumov, M. N., Marochnik, L. S. 98o, 1966. Dokl. Akad. Nauk SSSR, 164, 1019, 1965. 1965, Amer. Math. Soc., Summer Seminar on Relativity Theory and 101. Lynden-Bell, D. Astrophysics. 1962, Vestnik Leningrad. gos. Univ., no. 19, 96. 102. Antonov, V. A. 1966, 14th Liege Symposium, Gravitational Instability and the Formation 103. Arny, T. T. of Stars and Galactic Structures. 1966, 14th Liege Symposium, Gravitational Instability and the Formation 104. Simon, R. of Stars and Galactic Structures. 1964, Astrophys. J., 139, 1217. 105. Toomre, A. 1963, Astrophys. J., 138, 385. 106. Toomre, A. 1966, 14th Liege Symposium, Gravitational Instability and the Formation 107. Graham, R. of Stars and Galactic Structures. 1963, Mon. Not. R. astr. Soc., 126, 299; 129, 321, 1965. 108. Hunter, C. 1964, Mon. Not. R. astr. Soc., 128, 195. 109. Sweet, P. A., McGregor, D. D. 1964, Observatory, 84, 42. uo. Sweet, P. A., McGregor, D. D. 1965, Mon. Not. R. astr. Soc., IJO, 97· III. Goldreich, P., Lynden-Bell, D. 1964, Astrophys. J., 139, I 195. 112. Lynden-Bell, D. 1966, Publ. astr. Soc. Japan (in press). IIJ. Owaki, N. 1964, Astrophys. J., I40, xos6, I067, 1529. II4. Ostriker, J, 1966, J. SIAM Appl. Math., 14, 876. us. Lin, C. C. 1965, Amer. Math. Soc. Seminar on Relativity and Astrophysics, Cornell u6. Lin, C. C. University. 1964, Astrophys. J., 140, 646. II7. Lin, C. C., Shu, F. H. 1966, Proc. nat. Acad. Sci., 55, 229. uS. Lin, C. C., Shu, F. H. 1965, Thesis, Harvard University. II9. Kalnajs, A. J. 1964, Astrophys. Norv., 9, 103. 120. Lindblad, B. 1966, Astrophys. J., 146, 8xo. 121. Julian, W. H., Toomre, A. 1965, Thesis, MIT. 122. Rehm, R. G. 1964, Observatory, 84, 171. 123. Goldreich, P., Lynden-Bell, D. 1965, Mon. Not. R. astr. Soc., IJO, 125. 124. Goldreich, P., Lynden-Bell, D. 1965, NATO Summer Course 'Kinematical and Chemical History 125. Lynden-Bell, D. of the Galaxy', Herstmonceux. 1966, IAU-URSI Symposium no. 31, Noordwijk. 126. Prendergast, K. 1966, 14th Liege Symposium, Gravitational Instability and 127. Buggish, H., Kahn, F. D. the Formation of Stars and Galactic Structures. 1966, 14th Liege Symposium, Gravitational Instability and the Formation 128. Helfer, H. L. of Stars and Galactic Structures. 1966, 14th Liege Symposium, Gravitational Instability and the 129. Contopoulos, G. Formation of Stars and Galactic Structures. 1963, Mon. Not. R. astr. Soc., 128, 207. 130. Lyttleton, R. A., Bondi, H. 1966, Observatory, 86, 57· IJI. Lynden-Bell, D. 1966, 14th Liege Symposium, Gravitational Instability and the 132. Lynden-Bell, D. Formation of Stars and Galactic Structures. 1966, Mon. Not. R. astr. Soc., 134, 37· IJJ. Freeman, K. C., Mestel, L. 1963, Acta Astr., IJ, I. 134· Pacholczyk, A. G. 1963, Acta Astr., IJ, 30. 135· Stodolkiewicz, J. S. 1966, 14th Liege Symposium, Gravitational Instability and the Formation 136. Graham, R. of Stars and Galactic Structures. 1965, Astr. Zu., ..p, 515 = Sov. Astr., 9, 408, 1965. IJ7· Pikel'ner, S. B. 1963, Sci. Rep. Tohoku Univ. (Sendai), Ser. 1, 47, 165. 138. Fujimoto, M. 1965, Suppl. Progr. Theor. Physics, no. 31, 77· 139· Oki, T., Fujimoto, M., Hitotuyanagi, Z. 1965, Publ. astr. Soc. Japan, 17, 231. 140. Fujimoto, M. 1966, Bull. astr. Inst. Netherlds, 18, 51. 141. Setti, G. 1966, Mon. Not. R. astr. Soc., IJJ, 213. 142. Hornby, J, M. 1964, Acta Astr., 14, 81. I4J· Stepien, K.

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I44. Greyber, H. D. 1966, 14th Liege Symposium, Gravitational Instabihty and the Formation of Stars and Galactic Structures. I45· Pratap, R. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. I46. Sakakibara, S. 1965, J. Geomagn. Geoelectricity, I7, 99· 1964, 13th Solvay Conference, Brussels. I47· Woltjer, L. I48. van de Hulst, H. C. 1966, IAU-URSI Symposium no. 31, Noordwijk. I49· Davies, R. D., de Jager, G., Verschuur, G. L. 1966, Nature, 209, 974· ISO. Downes, D., Maxwell, A. 1966, IAU-URSI Symposium no. 31, Noordwijk. ISI. Burbidge, G. R., Hoyle, F. 1963, Astrophys. J., 138, 57. I 52. Lequeux, J. 1963, Ann. Astrophys., 26, 429. IS3· Ishida, K. 1964, Suppl. Progr. Theor. Physics, no. 31, II6. IS4· Pikel'ner, S. B. 1966, IAU-URSI Symposium no. 31, Noordwijk. 1966, Astrophys. J., 143, 400. ISS· Spitzer, L., Saslaw, W. C. 1964, The Origin of Cosmic Rays, Pergamon Press. IS6. Ginzburg, V. L., Syrovatskii, S. I. IS7· Rosen, S. 1966, 14th Liege Symposium, Gravitational Instability and the Formation of Stars and Galactic Structures. rs8. Mestel, L. 1963, Mon. Not. R. astr. Soc., 126, 553· 1965, Astrophys. J., 142, 1431. IS9· Lin, C. C., Mestel, L., Shu, F. H. 1966, Mon. Not. R. astr. Soc., 134, 109. 160. Grzedzielski, S. I6I. Milder M. 1966, Astrophys. J., 145, 109. 162. Carom, G. L. 1966, Besanyon Colloquium 'Nouvelles Methodes de la Dynamique Stellaire'. 163. King, I. 1965, Astr. J., 70, 296. 164. Genkin, I. L. 1965, Trudy astrofiz. Inst. Alma-Ata, s, 23. 165. Kuzmin, G. G. 1964, Tartu astr. Obs. Publ., 34, 9· 166. Kitamura, S. 1966, J. astr. Soc. Japan, 18, 317. 1965, Mon. Not. R. astr. Soc., 129, 299· 167. Lynden-Bell, D. 168. Avner, E. S. 1965, Dissert. Abstr., :z6, 27. B.

J.

BOK

President of the Commission

APPENDIX. REPORT OF THE COMMITTEE OF 'SELECTED AREAS' CHAIRMAN: Dr T. Elvius, Astronomiska Observatoriet, Uppsala, Sweden. MEMBERS: Kharadze, McCuskey, Plaut. Introductory notes This committee serves in continuation of the previous Commission 32 and Sub-commission 33c (Trans. IAU, nB, 333, 1962). For a list of reports prior to those in Trans. IAU, nA, 389, 1962, and uA, 548, 1965, see Trans. IAU, nA, 397, 1962. In the fifth volume of the series 'Stars and Stellar Systems' is an appendix by A. Blaauw and T. Elvius (I) giving a brief summary of Kapteyn's Plan of Selected Areas with a table of the centres of the areas of hi: Systematic Plan. In the following these areas are referred to as SA. At the Hamburg meeting of IAU it was decided that this committee should deal also with plans for co-operative galactic research supplementing the Kapteyn Plan (Trans. IAU, uB, 317, 1966). In order to avoid waste of space, most reports on such work, e.g. on the results of work in the Parenago Plan (52) or on the Cleveland fields, cf. (53) are included only in the main report of Commission 33·

720

COMMISSION 33 Progress of research

1. Durchmusterung and maps H. Vehrenberg has edited an Atlas (2), covering the Harvard-Groningen fields of SA 1-2o6, with pg-magnitudes of star sequences indicated.

2. Photometry Abastumani (Mt Kanobili). E. K. Kharadze reports on catalogues which have been published for regions in Parenago's Plan (52). E. K. Kharadze, S. P. Apriamashvili and T. A. Kotchlashvili (3) give pv-magnitudes for about xooo stars in Parenago field III (in Cygnus), identical with SA 40. S. P. Apriamashvili (4) publishes pg-magnitudes and CI for nearly 1900 stars in Parenago field I (in Aquila and Scutum) which includes SA 110. N. P. Kalandadze's catalogue (5) for Parenago field IV (in Taurus), which includes SA 49 and touches SA so, contains photographic UBV data for about 36oo stars. Another group of papers has just been printed: S. P. Apriamashvili and V. I. Kutznetsov give pg- and pv-magnitudes for a region within Parenago field I (in Aquila) at SA 87 (6). A catalogue of magnitudes and colours in the UBV system for stars in Parenago field III (Taurus) is published in two parts by N. B. Kalandadze (7); two selected areas are in this region. A paper by A. D. Chuadze (8) gives pg-magnitudes for stars in one of the Parenago fields. Several of the Abastumani papers include spectral data, cf. Section 6.

Basel. Work on three-colour photometry in the RGU-system and partly also in the UBV-system has continued in SA 51, 54, 57, 71, 82, 94, 107, 133, 141, and 158. It is aimed at a limiting magnitude of 19, but for some fields photoelectric standards are available only to 16 or 17. For SA 51 and 57 the results are ready, cf. (48). Berkeley. King is determining B, V, and R magnitudes in SA 51, 57, and 68, down to the limit of the 120-inch Lick reflector. The faint photometry is based on unpublished P and V photoelectric scales by Baum. Cape. Among the sooo stars included in the catalogue of photoelectric magnitudes and colours of southern stars by A. W. J. Cousins and R. H. Stoy (9), there is a considerable number of stars in Kapteyn's SA. Cracow and Crimea. E. Rybka (Cracow) reports that the catalogue of photoelectric magnitudes and colours for photometric standard stars in Selected Areas 1-139 has now been published (10). It is the result of cooperative efforts between S. V. Nekrasova and V. B. Nikonov of the Crimean Astrophysical Observatory and himself. The observations and methods have been previously described (54). The catalogue contains magnitudes and colours, both in the natural ubv and in the UBV systems, for two 6 magnitudes stars in each area, of A and K spectral type respectively. In cooperation with Abastumani Observatory it is planned to extend the scheme to include three A and K type pairs of V = 7"5, 9·o and xo·s in each of SA I-43· Rybka mentions the desirability of extending his plan also to the remaining southern Selected Areas. Engelhardt (Kazan). L. Urasin reports on the programme mentioned in the previous report. For SA 24-27 the photographic material has been obtained; its relation to the UBV system is described in (n). For SA 25 a catalogue of magnitudes and colours of 4700 stars has been published (12). Haute-Provence (Saint Michel) and Lyon. J. H. Bigay reports on the previously announced investigation of 0, B, and Ao stars in galactic areas, where photoelectric UBV measurements are made. Results have been published for SA 8 (13, 14) and previously for SA 9, 19, and 24 (55). For SA 40, 49, 64, and I 10 the observations are finished and ready for publication. For preliminary reports on SA 40 and 64, cf. (15, 16). Observations are going on in SA 74

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and 98. For SA 55-58, close to the north galactic pole, a similar programme for about 2oo A stars is nearly ready. These investigations are performed in collaboration with Mme M. Lunel. A programme for narrow-band photometry in nine regions from A. 36oo-5oooA for determination of Stromgren parameters and hydrogen line intensities has been initiated. Photoelectric measurements have been finished for SA 40, 64, 87, and 110, are on way for SA 9, 19, 24, and 49, and are planned for SA 8, 74, and 98. A. Terzan has published a photometric study of the central condensation of the Galaxy, for which SA 57 was used as standard field (17). From plates taken at the Haute-Provence Observatory magnitudes in blue, red, and infrared have been derived for about 300 stars in SA 57, down to the limit 19'3 (pg). Terzan has published a catalogue (18) giving blue, red and infrared magnitudes for 26oo stars in the above-mentioned region including SA 157. Kiev. V. I. Voroshilov reports from the Golossejev Central Astronomical Observatory of the Ukrainian Academy of Sciences on continued investigations into the Parenago fields. Voroshilov has published a catalogue (19) of pv-magnitudes for an area centered at oc = 19h, S = + 11° within the Parenago field I, previously treated (56). G. L. Fedorchenko has published pg- and pv-magnitudes (2o) for stars in the region of SA 87 also within Parenago's field I, cf. (57). Three-colour photometry will be undertaken for eight regions from Aquila to Cygnus and at the anticentre (including SA 19, 64, and 87) for an investigation in cooperation with Abastumani Observatory, which takes care of the spectral determinations. Lund. C. Roslund reports on a photometric investigation in cooperation with K. Sarg of a part of SA 195, based on plates taken with the Uppsala Schmidt telescope on Mt Stromlo in ultraviolet, blue and yellow light (limiting magnitude 15·2 in V). They take advantage of G. Lynga's photoelectric sequence Sq III in SA 195 (21) derived from Mt Stromlo and Bingar observations. Mt Palomar (Pasadena). H. M. Johnson has taken multicolour plates of SA 132 in connection with a search for the optical identification of the brightest X-ray source in Scorpius. Mt Stromlo (Canbe"a). B. J. Bok has, in collaboration with Mrs J. Basinsky, completed the photometric work in SA 141, situated at the south galactic pole (22). Photographic V and B- V are given for over 1400 stars, and photoelectric V and B- V for 26 standard stars. Observations have been made for SA 161, 169, and 205. B. Westerlund has published an infrared survey of the region of SA 193 (23) giving !-magnitudes and R-1 colours for about 300 stars. Radcliffe (Pretoria). A. D. Thackeray reports that photoelectric UBV photometry is being carried out in SA 162 by P. J. Andrews to V = 16. Stockholm (Saltsjobaden). K. Loden reports on the programme based on material from the Boyden Observatory (Trans. !AU, uA, 392, 1962) that for SA 193 photographically determined B and V magnitudes are ready for publication (limiting magnitude: B = 13·o; number of stars 447; size of area 1·0 sq. deg.). Photoelectric UBV measures for 21 stars serve as standards. For SA 192 the photometric results are nearly completed. Sternberg (Moskva). For a 45 square degrees field centered on oc = oh 30m, and S = + 62°, which includes SA 8, E. S. Brodskaya and N. B. Grigorieva (22a) have published a catalogue, with maps, giving, for nearly 2700 stars brighter than magnitude 12, photographically determined V and B - V, together with spectral types. Tartu. In connection with an investigation of eclipsing variables H. Albo has derived a photometric sequence in SA 18 (24). Toulouse. R. :Bouigue reports on a spectral and photometric investigation for determination of accurate stellar distances in selected regions. Observations have been performed in 5° x 5° fields at the north galactic pole (with SA 57) and the galactic anticentre direction (including

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SA 49). For UBV and narrow-band photometry(>. 3525, 3864, 4250, and 4990; band-width 7o-goA) the same equipment with a Lallemand photomultiplier was used at the Toulouse, Haute-Provence, and Pic du Midi observatories (25). The programme is enlarged to include the direction and antidirection of galactic rotation (close to SA 40 and I72 respectively). Tubingen. U. Haug reports on the photoelectric UBV measurements made in South Africa for SA g6, Ioo, 108, and I I2. Results have been published (26) for 20I stars in these fields together with I20 stars of the southern UBV-system, including the Harvard E-regions; for E I, 6 and 7 the catalogue gives data for several stars. Some of these stars have also been measured from the northern hemisphere: in SA Ioo by Haug at Kitt Peak, Arizona, and in SA I I2 by K. Walter at Serra La Nave, Sicily. Uppsala. For SA 8-Ig, T. Elvius and L. Haggkvist have published photoelectric measurements of 73 relatively bright stars (27). For supplementing previous research (58) T. Elvius has derived photographic U-magnitudes for the region of SA I9 from plates taken with the Kvistaberg Schmidt telescope. Y. Ekedahl has concentrated his photometric work on SA 4· It should also be mentioned that SA 8 and I9 are covered by the Uppsala Milky Way Survey, Part III, by T. Oja (28), who also gives a useful survey of photoelectric data for the investigated galactic strip. T. Elvius and G. Lynga have published UBV photometry for 43 stars in SA 68, 92, I38, I64, I65, I88, zoo, 20I, 204, 205, and zo6, measured at the Bingar Station of the Mt Stromlo Observatory (29). This programme has been continued by Lynga and C. Roslund at the Siding Spring Observatory. They have also carried on observations with the Uppsala Schmidt on Mt Stromlo for areas at southern latitudes. From plates taken with the same telescope P. I. Eriksson has practically completed photographic determination of blue and yellow magnitudes for nearly IO ooo stars in a 30 sq. deg. field at the south galactic pole, which includes SA 141. Vatican (Castel Gandolfo). M. F. McCarthy and P. J. Treanor have in collaboration with A. R. Upgren (now at van Vleck Observatory) begun a programme for studying stellar densities at intermediate latitudes by spectral and photometric observations within SA 28, 54, 106, and IOJ, cf. Section 6. Photometric plates have been taken with the 40 em refractor. Cf. (59). Warner and Swasey (Cleveland). S. W. McCuskey has published an investigation of a 25 sq. deg. area centered on SA I58 (30). For nearly IJOO stars pg-magnitudes are given and for 275 of them also colours, approximately in the B- V system. The plates were taken at the Bosscha Observatory, Lembang. The investigation published by D. Philip of a region (HLFz) in Pegasus includes the field of SA go (31). The catalogue gives photographically determined blue magnitudes; for standardization a special UBV sequence was observed at the Kitt Peak and McDonald observatories. For further information on the Cleveland fields in low, intermediate and high latitudes reference is made to the main report of Commission 33· Washington. From the Naval Observatory has been published a catalogue by D. L. Harris III and A. R. Upgren (32) which gives photoelectric magnitudes and colours in the UBV system for z8o BD-stars in a region at the north galactic pole which is identical with SA 57· The observations were made at the McDonald Observatory. V. M. Blanco reports that J. Priser has at the Flagstaff Station completed a photoelectric survey of I I I stars in even numbered SA of the 0° + 30° and + 6o 0 declination zones (33). Miss N. Roman, now with NASA, reports on her photoelectric work in a number of SA. The UBV observations are now reduced for nearly 8oo stars in 40 areas. Generally, all proper-motion reference stars are included in the areas where observations ~ave been made.

3. Variable stars Hamburg-Bergedorf. The series of catalogues of variables in the southern part of the Cygnus

STRUCTURE DU SYSTEME GALACTIQUE

723

cloud by A. A. Wachmann (34) include several stars in SA 64. Wachmann has also published catalogues of variables in the region of SA 98 in Monoceros (35). Harvard (Cambridge, Mass.). Miss M. Olmsted reports that she has obtained photographic and photored light curves for nine cepheids in SA 193 (35a). She is engaged in a search for more faint cepheids in the same area, using plates taken with the Baker-Schmidt telescope of the Boyden Observatory. Haute-Provence (Saint Michel) and Lyon. Terzan has published identification charts for new variable stars at the central condensation of the galaxy (36, 37); the field includes SA 157, cf. (18). Lick (Mt Hamilton). T. D. Kinman, C. A. Wirtanen and K. A. Janes have in the course of the RR Lyrae star survey with the 20-inch (51 em) astrograph published results for three fields near the north galactic pole (38); field RR 4 coincides with SA 57 whereas fields RR 2 and 3 are between this and SA 56. For SA 57 a couple of faint stars have been added to the photoelectric sequence by J. Stebbins, A. E. Whitford and H. L. Johnson (6o). Kinman reports that the extended RR Lyrae programme will include SA 61; a survey of variables of longer period will include SA 27 and 28. 4· Proper motions and positions Bonn. H. van Schewick reports the intention to measure relative proper motions for the northern SA which remain after the publication of data for 18 galactic fields, cf. Trans. !AU, 12A, 550, 1965. SA 72, 95, and II5 have already been measured and relative proper motions have been derived. For SA 40 two more pairs of plates were measured in connection with an investigation of the galactic cluster An. Barkh. I (39). Similarly the proper motions of SA 98 have been used for a study of NGC 2301 (40). The results of the determination of the solar apex from high-velocity stars, mentioned in the last report, will soon be published. van Schewick has prepared a list of proper motions for variable stars, including several SA objects. Greenwich (Herstmonceux). The possibility of improving the proper motions in SA is considered by C. A. Murray. The old Radcliffe Catalogue (61) should be used as 'first epoch' and be combined with plates taken with the 26-inch (66 em) Greenwich refractor in addition to those obtained with the Radcliffe telescope at London Observatory, cf. Trans. !AU, 12A, 551, 1965. The first area to be investigated is SA 57 at the north galactic pole. 5· Radial velocities David Dunlap (Richmond Hill). J. F. Heard has published radial velocities and spectral classes of 55 fundamental stars in the high-latitude areas SA 13-15, 29-35, and 53-60 (41). Haute-Provence (Saint-Michel) and Marseille. The following information has been obtained from Ch. Fehrenbach, in addition to the report in Trans. !AU, 12A, 551, 1965. Concerning work with the smaller objective prism (PPO): (a) Results have been published for SA 9, 21, 29, 30, 46, 67, 69, 75, 90, 91, 94, and II3 by Ch. Fehrenbach, M. Duflot, J. Boulon, E. Rebeirot, and C. Lanoe (42). (b) Results are close to publication for SA 41 and 43· (c) Measurements are going on for SA 3, 4, 13, 22, 23, 35, 37, 39, 61, 62, 66, 68, 81, 85-88, 98, and n4. Concerning work with the larger prism (GPO): (d) Results are ready for publication for SA 15 and SA 19, northern part. (e) Measurements are on way for SA 9, II, 13, 36, 40, 41, 53> 58, 59, 6I, 64 centre, 64 north, 81, and no.

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Measurements have been published during the years for altogether 1432 stars, of which 736 belong to types 0, B, and A, and 696 to types F, G, K, and M. Observations have also been made of a certain number of regions within the Parenago fields; results have been published for an area in field IV (42 p. 185). Radcliffe (Pretoria). A. D. Thackeray reports that slit spectroscopy will be undertaken by T. Lloyd Evans for stars down to V about 12 in SA 141 at the south galactic pole. 6. Spectral and luminosity classification; absolute magnitudes Abastumani (Mt Kanobili). Spectral types and luminosity classes are given in the catalogues mentioned above in Section 2, for stars in Parenago fields, including some SA (3-8). Investigations are going on for a number of regions in Taurus and Aquila. Two-dimensional spectral classification is planned for a series of areas uniformly distributed in the equatorial plane from Aquila to Cygnus and at the anticentre for which the photometric work will be undertaken by the Golossejevo Observatory at Kiev, cf. Section 2. David Dunlap (Richmond Hill). Spectral classification in the MK system is included in the paper (41), cf. Section 5· Engelhardt (Kazan). The previously reported spectrophotometric investigation of SA in the + 45° declination zone is continued, cf. Section 2. Haute-Provence (Saint-Michel) and Marseille. In continuation of (62) Mme M. Barbier has published two lists of M, S, and C stars in several fields, among them Kapteyn areas in the declination zones + 75°, + 45°, + 30°, + I5° and 0° (43). She has also determined absolute magnitudes for 200 0, B, and A stars in SA 8 by spectrophotometric measurements of objective prism plates (44). The catalogues referred to above in Section 5 as (42) include spectral and luminosity classification for a considerable number of SA stars. Here should also be mentioned the paper by Mme N. Martin (45) on the determination of absolute magnitudes by 'bhman's method' (63, 64). Her catalogue for the Carina field includes stars in SA 193, whereas SA 18 is just outside the Cepheus field. Kiev. Spectral classes have now been published by Voroshilov (46) for 3500 stars in two of the sub-regions in Aquila within Parenago field I, for which photometry has been reported (19 and 56). Cf. also I. I. Pronik's catalogues from the Crimean Astrophysical Observatory (65). Spectral classes are also included in Fedorchenko's catalogue for stars in the same Parenago field (zo), mentioned in Section 2. Radcliffe (Pretoria). MK classification will be included in the programme for SA 141 reported in Section 5· There are also plans for spectroscopy of stars within other southern SA in the R.A. range from zoh to zh. Sternberg (Moskva). Spectral types have been published for a field including SA 8; cf. Section 2. Stockholm (Saltsjobaden). Spectrophotometrically derived spectral types and luminosity classes are included in the investigation of SA 193 just terminated by K. Loden, mentioned in Section 2. Toulouse. Spectrophotometric measurements from objective-prism plates are planned for the fields mentioned in Section 2 for determination of absolute magnitudes from equivalent widths of hydrogen lines. Uppsala. For the Stockholm and Uppsala SA programmes reported in Trans. !AU, nA, 394 and 395, 1962, additional plates have been taken with the Uppsala Schmidt telescope on Mt Strornlo by Roslund and Lynga. Eriksson's spectral measurements for the region of SA 141 are now ready. Oja's catalogue (28) mentioned in Section 2 includes data for stars in SA 8 and 19.

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Van Vleck (Middletown, Conn.) and Vatican. A. R. U pgren has in collaboration with McCarthy and Treanor of the Vatican Observatory, cf. Section 2, outlined an observational programme to determine the inclination of plane-parallel layers of stellar density to the galactic plane. The regions chosen are SA 28, 54, 106, and 107. Spectral plates have been taken with the 24-inch (61 em) Baker-Schmidt telescope of the Dyer Observatory, Nashville, and also, for smaller dispersion, with the Schmidt telescope of the Vatican Observatory. Warner and Swasey (Cleveland). Spectral types and luminosity classes have been published for SA 158 stars by McCuskey (3o), and for stars in SA go by Philip (31).

7· Polarization Gottingen. Stars in SA 40 and 97 are included in a polarimetric, photometric and spectroscopic investigation of stars in Cygnus and Orion by I. Appenzeller (47).

8. Investigations based on the material of Selected Areas Several of the papers referred to above in the SA report and in the main report of Commission 33 contain investigations of galactic structure based on SA material. Of special interest for the future is an investigation by W. Becker aiming at derivation of star densities in the galactic halo by means of three-colour photometry. The SA included in the observational programme were mentioned in Trans. !AU, 12A, 548, 1965. A first paper treating SA 51 has been published (48), cf. also (66). In (44) Mme Barbier investigates the absorption, the stellar distribution and the galactic rotation in the Cassiopeia field SA 8. Here should also be mentioned the extensive study of stellar distribution near the south galactic pole (22) by B. J. Bok and J. Basinski. It is based on photometric measurements in SA 141. The density decrease with z is derived for A and F type stars, thereby supplementing the discussion by T. Elvius (49) in his summarizing paper on the distribution of common stars in intermediate and high galactic latitudes, for which data from Selected Areas are fundamental. In this paper Elvius presents some not previously published results derived from the third Stockholm SA catalogue (67). Studies of the distribution of stars and interstellar matter, based on data from the Kapteyn and Parenago fields, have been published by L. N. Kolesnik (so) for the Cygnus field SA 40 = Parenago region II), and by Fedorchenko for the Parenago region I in Aquila (20, 51). Desiderata for future work

Several members of the Commission 33 have expressed their view that the Selected Area Committee should once more emphasize the need for more observational data in the SA and similar fields in accordance with the Desiderata of the previous report, Trans. IA U, 12A, 553> 1965. Especially has been stressed the importance of having, for kinematical studies, more and better proper motions and radial velocities of faint SA stars. The value of such work would be increased if photoelectric data could be obtained for as many as possible of these stars. It is obviously difficult in many cases to get a satisfactory survey of the existing data. The desire has therefore been expressed that for each individual area summaries should be prepared, facilitating the exploitation of existing material and also the planning for supplementary data. T. ELVIUS

Chairman of the Committee

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a. New Selected Area data and investigations I965, Stars and Stellar Systems, Gen. eds. G. Kuiper and B. 1. Blaauw, A., Elvius, T. Middlehurst, Vol. 5, Galactic Structure. Eds. A. Blaauw and M. Schmidt, 589, University of Chicago Press, Chicago. I965, Atlas of Harvard-Groningen Selected Areas, Treugesell2. Brun, A., Vehrenberg, H. V erlag, DUsseldorf. I964, Abastumani astrophys. 3· Kharadze, E. K., Apriamashvili, S. P., Kotchlasvili, T. A. Obs. Bull., 31, 3· I964, ibid, 31, 27. 4· Apriamashvili, S.P. I964, ibid., 31, 66. 5· Kalandadze, N. B. I966, ibid., 35· 6. Apriamashvili, S. P., Kuznetsov, V. I. I966, ibid., 35, and 7· Kalandadze, N. B. I966, ibid., 35· 8. Chuadze, A. D. I963, R. Obs. Bull., no. 64. 9· Cousins, A. W. ]., Stoy, R. H. I965, lzv. Krym. astrofiz. Obs., 34, 69. 10. Nekrasova, S. V., Nikonov, V. B., Rybka, E. I96s, Bull. astr. Obs. Engelhardt (Kazan), as. 47· II. Urasin, L. I966, Izv. astr. Obs. Engelhardt (Kazan), no. 35· 12. Urasin, L. I965, C.R. Acad. Sci., Paris, 260, 3853. 13. Bigay, ]. H., Lunel, M. 1965, J. Observateurs, 48, I7I = Publ. Obs. Hte-Provence, 8, 14. Bigay, ]. H., Lunel, M. no. 7· 1966, C.R. Acad. Sci. Paris, 262 Ser. A-B, I570 = Publ. Hte-Provence, 8, 15. Bigay, J. H. no. 28. I966, ibid., 263 Ser. A-B, 214 = Publ. Hte-Provence, 8, no. 29. 16. Bigay, ]. H. 1965, Ann. Astrophys., 28, 935 = Publ. Obs. Hte-Provence, 8, no. I2. 17. Terzan, A. I966, J. Observateurs, 49, 225 = Publ. Obs. Hte-Provence, 8, no. I2 vis. 18. Terzan, A. 1966, Problems of astrophysics, 136. 'Naukova Dumka', Kiev. 19. Voroshilov, V. I. 1964, Investigations of the physics of stars and diffuse matter, 63. 20. Fedorchenko, G. L. 'Naukova Dumka', Kiev. I964, Acta Univers. Lund, Sect. II, no. I I = Medd. Lunds Obs., Ser. II, no. I39· 21. Lynga, G. I964, Mem. Mt Stromlo Obs., no. I6. 22. Bok, B.]., Basinsky, J. I964, Soob!c. gas. astr. lnst. Sternberga (Moskva), 2:za. Brodskaya, E. S., Grigorieva, N. B. no. 136. I965, Mon. Not. R. astr. Soc., 130, 45 = Mt Stromlo Obs. Repr., no. u6. 23. Westerlund, B. 1964, Tartu astr. Obs. Publ., 34. I69. 24· Albo, H. I965, J. Observateurs. 25. Azzopardi, , Bouigue, R. 1966, Z. Astrophys., 64, 116 =Mitt. astr. Inst. Tiibingen, 26. Pfleiderer,]., Dachs, J., Haug, U. no. 88. 1966, Ark. Astr., 4, no. 3 = Uppsala astr. Obs. Medd., no. 152. 27. Elvius, T., Hiiggkvist, L. 1966, Nova acta reg. soc. sci. Upsal., Ser. IV, 19, no. 3 = Uppsala astr. Obs. Ann., 28. Oja, T. 2, no. 4· 1965, Ark. Astr., 3, no. 32 = Uppsala astr. Obs. Medd., no. 149. 29. Elvius, T., Lynga, G. 1964, Astr. J., 69, I04 = Warner and Swasey Obs. Repr., no. 128. 30. McCuskey, S. W. I966, Astrophys. J. Suppl., 12, 39I = Warner and Swasey Obs. 31. Davis Philip, A. G. Repr., no. 142. I964, Astrophys.J., 140, ISI = U.S. nav. Obs. Washing32. Harris, D. L. III., Upgren, A. R. ton Repr., no. 52. I966, Publ. astr. Soc. Pacific, 78, 474, U.S. Naval Obs. Washington, Repr., 33· Priser, ]. B. no. 79· Astr. Abh. Hamburg. Sternw., 6, no. I, I96I; no. 2, 1963; no. 3, I964; 34· Wachmann, A. A. no. 4, I966. ibid., 7, no. 3 and 4, I964; no. 7, I966. 35· Wachmann, A. A. 1966, Astr. J., 71, 916. 35a. Olmsted, M. I96s, c. R. Acad. Sci. Paris, 261, 3974 = Publ. Obs. Hte-Provence, 8, no. I I. a6. Terzan, A. I966, J. Observateurs, 49, 258 = Publ. Obs. Hte-Provence, 8. 37· Terzan, A.

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1966, Astrophys.J. Suppl., IJ, 279 = Contr. 38. Kinman, T. D., Wirtanen, C. A., Janes, K. A. Lick Obs., no. 202. I966, Verii.ff. Univ. Sternw. Bonn, no. 74· 39· van Schewick, H. I966, ibid., no. 76. 40. van Schewick, H. I965, Publ. David Dunlap Obs. Univ. Toronto, 2, no. I6. 41. Heard,]. F. I966, J. Observateurs, 42- Fehrenbach, Ch., Duflot, M., Boulon, J., Rebeirot, E., Lanoe, C. 49. ISS. IS8, x6s, I76, I94. and 205 = Publ. Obs. Hte-Provence, 8, no. 25· I966, J. Observateurs, 48, I49, and 49, 290, = Publ. Obs. Hte-Provence, 8, 43· Barbier, M. no. 5 and no. 30, 23. I966, J. Observateurs, 49, 269 = Publ. Obs. Hte-Provence, 8, no. 30, I. 44· Barbier, M. I964, J. Observateurs, 47, 125 = Publ. Obs. Hte-Provence, 7, no. 33· 45· Martin, N. I966, Physics of stars and interstellar medium, 92. 'Naukova Dumka' Kiev. 46. Voroshilov, I. I. I966, Z. Astrophys., 64, I9 = Veroff. Univ. Sternw. Gottingen, no. 144. 47· Appenzeller, I. 1965, Z. Astrophys., 62, 54= Mitt. astr-meteor. Anst. Univ. Basel, no. 40. 48· Becker, W. 1965, Stars and Stellar Systems, 5, Galactic Structure. Eds. A. Blaauw and M. 49· Elvius, T. Schmidt, 4I, University of Chicago Press, Chicago. I964, Investigations of the physics of stars and diffuse matter, 52. 'Naukova 50. Kolesnik, L. N. Dumka', Kiev. 1966, Problems of astrophysics, 169. 'Naukova Dumka', Kiev. 51. Fedorchenko, G. L. b. Other references I956, Astr. Zu., JJ, 749· See also !AU Symp., no. 7, 6I, I959· 52· Parenago, P. P. I965, Stars and Stellar Systems, Gen. eds. G. Kuiper and B. Middle53· McCuskey, S. W. hurst, s: Galactic Structure, Eds. A. Blaauw and M. Schmidt, I, University of Chicago Press, Chicago. 54· Trans. !AU, 12A, 554, ref. 5, I965. 55· Trans. IAU, 12A, 554, ref. I I and I2, I965. s6. Trans. !AU, I2A, 554. ref. 9a, I96s. 57· Trans. !AU, 12A, 554, ref. 9c, I965. 58. Trans. !AU, 9, 472, ref. 62, I955· I965, Ann. rep. Vatican Obs., 59· O'Connell, D. J. K. 6o. Trans. !AU, 9, 470, ref. 16, I957· 61. Trans. !AU, 9, 47I, ref. 36, I957· 62. Trans. IAU, 12A, 554, ref. 29-3I, I965. I930, Medd. Astr. Obs. Uppsala, no. 48. 63. Ohman, Y. I958, Handbuch Physik, Ed. S. Fliigge, so, 25. Springer Verl., Berlin. 64. Fehrenbach, Ch. 65. Trans. !AU, 12A, 534, ref. Io, I965. I966, !AU Symp., no. 24, 358. 66. Becker, W. 67. Trans. IAU, nA, 397, ref. 8, 1962.

P2

34. COMMISSION DE LA MATIERE INTERSTELLAIRE ET DES NEBULEUSES PLANETAIRES PRESIDENT: Professor S. B. Pikelner, Sternberg Astronomical Institute, Moscow B-234, U.S.S.R. VICE-PRESIDENT: Professor D. E. Osterbrock, Washburn Observatory, University of Wisconsin, Madison 6, Wisconsin, U.S.A. MEMBRES: Aller (L. H.), Andrillat (H.), Andrillat (Y.), Behr, Bok (B. J.), Chvojkova, Courtes, Divan, Dunham, Elvius (A. M.), Gehrels, Goldsworthy, Greenberg, Gurzadian, Hall (J. S.), Haro, Henize, Hiltner, Herbig, Johnson (H. M.), Kahn, Kaplan (S. A.), Kerr, Kharadze, Khavtasi, Kipper, Kohoutek, Lambrecht, Liller, Loden (L.), McCrea, Martel-Chossat, Menon, Minin, Minkowski, Mi.inch (G.), Pottasch, Razmadze (N. A.), Rosina, Rozhkovski, Safronov, Savedoff, Schalen, Schatzman, Schmidt (K. H.), SchmidtKaler, Seaton, Serkowski, Sharpless, Shklovsky, Sobolev, Spitzer, Stromgren, Takakubo, Thackeray, Treanor, van de Hulst, van Woerden, Vanysek, von Hoerner, VorontsovVelyaminov, Walker (G. A. H.), Westerhout, Whitford, Zimmermann (H.), Zirin. INTRODUCTION New fields of astrophysics, which arised recently, resulted in the enlargement of topics included into the list of problems of Commission 34· As far as the problems connected with quasars, structure of galaxies and their nuclei are concerned the review deals with questions relating to the diffuse medium. The review is partly based on the reports of Commission members, especially on those of Professor Osterbrock and Dr Aller. I am greatly obliged to Professor Greenberg, who kindly wrote a separate review on interstellar grains. Since 1964 several new books and reviews have appeared: Structure and Evolution of Galaxies, 1964, Suppl. Prog. theor. Phys., Osaka, no. 31. Osterbrock, D. E., 1964, A. Rev. Astr. Astrophys., 2, 95· Pottasch, S. R., 1965, Vistas in Astronomy, 6, 149· Kahn, F. D., Dyson, J. E., 1965, A. Rev. Astr. Astrophys., 3, 47· Stars and Stellar Systems, V: 1965, Galactic Structure Ed. by A. Blaauw and M. Schmidt, Univ. of Chicago Press, Chicago. Schalen, C., 1965, Publ. astr. Soc. Pacif., 77, 409. Kaplan, S. A., Pikelner, S. B., 1965, Izv. Akad. Nauk SSSR, fiz. ser., 29, 1830. Stars and Stellar Systems, VII: 1966, Nebulae and Interstellar Matter, Univ. of Chicago Press, Chicago. Dieter, N. H., Goss, W. M., 1966, Rev. mod. Phys., 38, 256. Kaplan, S. A., Pikelner, S. B., Interstellar medium, Harvard, in press. Symposium on Radio and Optical Studies of the Galaxy, 1966, Mount Stromlo Observatory. IAU Symposium no. 31, 1966, Radio Astronomy and the Galactic System, Noordwijk, Sept. (in press). PLANETARY NEBULAE During these years spectrophotometric observations of planetary nebulae were continued: absolute intensities of spectral lines and of continuum, in particular in peculiar and stellar-like objects, infrared and radio-observations. The classical theory of nebulae emission was improved. Transition probabilities and collision cross-sections for a number of ions were calculated. Theoretical investigations of the recombination spectra of H, He and of other elements were 729

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performed, especially for different /-values and for higher levels, where some anomalies were revealed. The chemical composition, in particular for nebulae of different sub-systems was defined more precisely. However the main progress now takes place in the investigation of the dynamics and evolution of nebulae, of their stratification, expansion, with simultaneous evolution of their central stars. This problem is particularly important, because planetary nebulae are advanced stages of the evolution of some types of stars, and a comparison of the central stars of different-age nebulae allows to find an evolutionary modification in blue dwarfs. Eighty-six planetaries were identified on Palomar Sky Survey by Abell (z). A catalogue of 202 new planetaries on the South Sky was published (2), and two nebulae were found (3). Perek and Kohoutek have prepared for publication an extensive catalogue with charts, containing more than 1000 planetaries with positions 195o·o, galactic coordinates, sizes, surface brightness, magnitude, classification and information on the central star (4). Westerlund and Smith revealed 42 planetaries in LMC (5), measured their colours and magnitudes. Spectra of 20 planetaries in other galaxies are being investigated. The determination of absolute proper motions in the system of FK4 for 16 planetary nebulae, with a mean error of ± o~oo8fyear, is reported by Dr Chr. de Vegt. Phtoelectric and photographic spectrophotometry was carried out for a large number of planetaries by Aller, Bowen, Czyzak, Faulkner, Liller, Kaler, O'Dell, Walker, Kohoutek (7, 8, 9, zo, n, 1:2, 1:3, 1:3a). Application of the Lallemand image converter made it possible to study in detail a visual part of spectra (z4). Absolute intensities of main lines were measured by photographic method in 65 northern and 90 southern nebulae (in the direction of the Galactic centre) by Vorontsov-Velyaminov, Kostyakova, Dokuchaeva, Arkhipova (zs, z6). Infrared line 12·8 p. Ne II was observed in IC 418 by Low (z7). The flux is I0-16 w cm-2 in agreement with theoretical estimation o·6 x Io-16 w cm-2 (z8, 1:9). Radio observations of planetary nebulae were carried out by Golnev and Parijsky (20), Khromov and others (2z), Menon and Terzian (22). Models of nebulae based on these observations were constructed (23, 24), which are in agreement with optical data. Transition probabilities for a number of permitted optical and ultraviolet lines of astrophysical interest were calculated by Czyzak, Aller and their associates (25, 26). Collision cross-sections for a fine-structure N III, 0 IV, Ne II were calculated by Osterbrock (27), and in (:z8) a general formula for the calculation of critical electron concentration is given. Dalgarno estimated A 2, 18 for two-photon transition of He I and the distribution of the energy in two-photon emission (28a). Capriotti (29) confirmed the conclusion by Osterbrock that 2s state is more important for optical depths of Balmer lines than 2p state, but the majority of planetaries are optically thin. Pengelly showed that the recombination spectrum of H and He II is not in agreement with observations for upper levels (30). It was necessary to take into account collisions transitions n,l-+ n,l + 1. Such calculations (31) including the radiation gave smooth transitions from the lines to the continuum (32). Similarly Kaler (33, 34) showed that in many planetaries higher members of H, He I, He II series are relatively brighter than in recombination theory. Discrepancies are not connected with parameters of nebulae and their origin is not clear. Clarke made more extensive calculations of stationary populations of sublevels, taking into account all effects. He obtained better agreement with observations than for the pure radiative decrement (35). The temperature of nebulae calculated inclusive the fine structure of ion levels is in agreement with observations (27). From the uniform material (zs, z6), physical parameters of nebulae were calculated (36). The importance of interstellar absorption was evaluated in

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(37). The temperature and density of IC 4997 were calculated by Gurzadian (38). He also showed that the inner part of ring-shape planetary nebulae is relatively hotter due to high ionization (39). Chemical composition of a number of nebulae (40) and an average composition (41) was calculated by Aller. The nebula in globular cluster M 15 contains few heavy elements but a normal abundance of He. Apparently He was in primordial matter. It makes the age of globular clusters shorter (42). The transfer theory for nebulae is developed in (43). In (44) the probability of escape LIX quanta is calculated numerically with frequency re-distribution and geometry. Accumulation of LIX in many cases greatly exceeds the theoretical value apparently due to H 1 shell around the nebulae (45). It is supported by the presence of [0 1] line which is an indicator of the nebulae optically thick in Lc (46). Mass, T * and other parameters for such nebulae are calculated in (47, 48). Stratification of nebulae, ionization of He in different layers and for stars of different temperature were evaluated in (49). The space structure of a nebula can be determined from its picture and spectrum (50). Expansion of nebulae was investigated on radial velocities (51). In several cases it was determined directly from proper motions (52, 53). In many nebulae there is no expansion, apparently due to a dense surrounding medium. Expansion was discussed theoretically in (54). The model of an expanding nebula, i.e. the distribution of the density, temperature and velocity with radial distance and with time was calculated by Mathews (55). He took into account the heating and cooling of the expanding gas and obtained the variation of Hf3 profiles and emission measure with time. To receive an agreement with the observations an additional stream of the gas from the central star is needed. This confirms that its activity is continued. A central star of WN type was first revealed by Bertola (56). Spectrophotometry of nuclei is given in (57). Determination of nebulae distances as well as temperatures and luminosity of their nuclei allows to draw evolutionary tracks from the left end of the horizontal branch to the white dwarfs (58, 59). The evolution of central stars was discussed also in (6o). In (61) a convection in cold variable supergiants-embryons of planetaries and the transfer of angular momentum into outer zone were discussed. The importance of rotation for detachment of the envelopes was stressed in (6z). Temperatures of the central stars were determined in (63, 64), the theoretical model and the spectrum of the central stars were calculated in (65, 66). Calculations on the theory of transfer of radiation in resonance lines (67, 68, 69, 70, 71, 72) can be applied to planetary nebulae. DIFFUSE NEBULAE AND H II REGIONS

Investigations of diffuse nebulae and H II clouds developed mainly in traditional directions. More precise evaluations of the spectrophotometry in optical and infrared lines and in continuous spectrum were carried out, a thermal continuous radio-emission was determined. An investigation of emission radio-lines of highly excited hydrogen is a new step in this field. This allowed to identify distant heavily obscured H II regions and to determine their radial velocities. This also permitted the calculation of temperatures. Some contradictions with the theory stimulated the development of the latter. Questions were elaborated on: dynamics of the nebulae expansion, their interaction with the surrounding gas, the influence of the dust on the structure of ionization and shock fronts, formation of globulae and of elephant trunks, internal motions in nebulae. The structure and origin of cometary nebulae and the fine filamentary structure of reflecting nebulae are also connected with the dynamics of the gas and with magnetic fields. Searches and investigations of emission regions in Magellanic Clouds and in other galaxies were continued.

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A catalogue of bright nebulae that appear on the Palomar Sky Survey was prepared by Lynds (73). The careful spectrophotometry of Orion Nebula in spectral region 3I87-50I6A was made by Kaler, Aller and Bowen (74). Relative intensities and identifications of lines up to I"5 x Io-4 H f3 are given, O'Dell and Hubbard (75) made a photoelectric scanning of lines and continuum of the Orion Nebula. The continuum moving from the Trapezium becomes bluer and brighter relatively to H {3. This is due to the light scattered by dust. Reitmeyer (76) made the photometry of the Orion Nebula images taken in selected wavelengths. Electron temperature determined from the ratio H f3 to the Balmer continuum is changed inside the nebula, it is higher where abundance 0 III is less. Some other results of the paper are not reliable as the influence of interstellar absorption was not taken into account (76a). The influence of the density fluctuations on the mass evaluation was discussed by Peimbert (77). He obtained a uniform temperature from the comparison 0 II and 0 III lines if the abundance of oxygen is constant. Wurm and Perinotto compared the structure of the Orion Nebula in lines and in the continuum (78). Profiles of IO 83oA He I in Orion were obtained by Voughan (79). Infrared observations by Moroz showed that, in o,85-I ·7 f.L, the main emission of this nebula is produced primarily by the gas, not by the dust (So). The intensity of [0 II] and the electron concentration were determined in several bright nebulae (81) and the spectrophotometry of the nebulae around 7J Carinae and 30 Doradus was made (82). In the central part of the Lagoon Nebula T = 9000°, Ne = 250 cm-3, and in two bright condensations- IO ooo 0 and I ·6 x 104 cm-3 respectively. The mass of the condensations is about o·7 M"' (83). Khachikian (84) determined the strong polarization of the Omega Nebula (I8%) with a constant direction and came to the conclusion that the emission of the Nebula is not connected with the reflection. But the photoelectrical measurements do not give values exceeding 4% (84a), and the polarization is undoubtedly of interstellar origin. Continuous radio-emission of the Rosetta Nebula gave (85) its emission measure, and observations of four nebulae on different frequencies showed the thermal origin of their emission (86). The thermal character of the spectrum is confirmed for a weak nebula near y Cyg (87). The structure of nebulae in radio-emission and the connection of the structure with stars in Orion are studied in (88). It was confirmed that the thermal source Cyg X is a large Stromgren sphere around the association VI Cyg (89) which is situated at the distance of I· 5 kps along the arm (90). Twenty separate sources on the general phone Cyg X are revealed in (91). All of them, except one, have the thermal spectrum. Thirteen galactic radio-sources were investigated at the ..\ = 6 em (92), their structure and brightness were determined. In the central region of the Galaxy there are several sources with thermal spectra (93, 94). Their thermal nature is confirmed by the lines of highly excited hydrogen. These lines were predicted theoretically long ago and were revealed recently (95, 96, 97). They are an important source of information as they allow to measure the radial velocity of the source and to separate thermal and non-thermal radio-emission. The intensity of these lines as well as the continuum are proportional to the emission measure but their dependence on temperature differs. Therefore their ratio permits to determine T, if the Doppler width is known (97). Such measurements for 20 sources gave T from 4000 to gooo 0 • Earlier, Burbidge and others (98) obtained theoretically such low temperatures, taking into account the excitation of the fine-structure of ground states of abundant ions. But they overestimated the collision crosssections. Osterbrock estimated once again the collision strengths for important transitions and showed that the expected temperatures are between 5000° and 10 ooo 0 • Temperatures of low-density nebulae are significantly lower than those of high-density nebulae, such as classical bright planetaries and the centre of the Orion Nebula (99). Observations of radio-lines deal with rather dense nebulae. O'Dell (100) measured the temperature from [0 m] lines

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in NGC 66r8 and NGC 6523 and in three rarefied planetaries and showed that they are in fact significantly lower than in the centre of the dense Orion Nebula. His measurements also gave a higher temperature than the theoretical one (98) and that from radio-lines. They agree better with Hjellming's calculations (Ioi), who used new models of high temperature stars and obtained T from 5700° to more than 8ooo 0 depending on the star temperature. An explanation of the temperature determined from radio-lines gave Goldberg (102). Populations of upper levels are practically the same as the equilibrium ones, especially if collisions are taken into account. However the lower the level, the more is the deviation from the equilibrium due to an increasing role of spontaneous transitions. The ratio of the population of two neighbouring levels deviates from the equilibrium one less than by ro-3 , but even such little relative overpopulation of upper levels gives a maser-effect and lines get brighter relative to continuum. It gives an anomalous low calculated temperature. The widths of the lines of highly excited hydrogen were also in disagreement with theoretical expectations. The accepted theory by Griem, Kolb and Shen (103), which takes into account electron impacts besides the statistical stark-effect, suggested a width considerably exceeding the observed value (104). Some laboratory experiments with hydrogen plasma also show widths less than the theoretical ones (105). These discrepancies were apparently a result of a wrong dependence of broadening by electrons ,\e '""(n5 + n' 5) in (103) and also of an incorrect extrapolation of the results found for the disturbance of one level for the general case of the disturbance of both initial and final levels (see (1o6)). Besides the hydrogen lines, higher transitions of helium were also observed (107). Palmer (107a) calculated the catalogue of radio-lines of hydrogen and helium. Temperature of the gas is connected with its movements. High temperature of H II regions in galactic nuclei, determined from [N II]: Hoc ratio, is explained in (98) by the influence of stellar winds, which is important in the regions with high star density. In (Ioi), there was calculated the structure of H II regions which are limited by an ionization front. The absorption of the radiation in the nebula, scattered radiation and cooling due to the excitation of levels and sublevels of iones were taken into account. The dynamics of the expansion of H II regions was discussed by Axford who took into account the absorption of stellar radiation at the early stage of expansion (Io8) and showed that the stability of weak ionization fronts of D-type increases due to this absorption (109). Vandervoort (no) calculated the age of the Orion Nebula (14-23 thousand years) from the comparison with the theoretical model. He calculated the early stage of the expansion of H II region (before the radius has reached the Stromgren radius), the propagation of the ionization and shock fronts, and investigated the non-stationary ionization front formed by a star with a varying flux of radiation (In). Lasker (112) discussed the later stage of expansion of H II regions with the age of about 2 million years. Goldsworthy (n3) investigated the influence of gravitation on the central part of H II region and found a more precise age of the Orion and Rosetta. Mathews (n4) discussed the expansion of the nebula with the massive central star which has a considerable evolution during the expansion of the nebula. He evaluated all main processes of heating and cooling and found a model of physical conditions, velocity field in H II and parameters of a shock wave in H I with time. The maximum temperature is expected immediately behind the ionization front. He believes that the formation of a central hole in Rosetta and in similar objects can be explained by the pressure of 'winds' from the stars which are situated inside or by a condensation of a part of the gas in stars ( ns). According to radio-observations the low-latitude regions H II are surrounded by H r, the main part of which does not expand. High-latitude regions are not associated with a considerable amount of HI (n6). Apparently H II regions are immersed into large complexes of neutral hydrogen.

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An estimation of the ratio of dust to neutral hydrogen density in Cas and Sge was done in (n6a). The presence of dust in the ionization and in shock fronts has an influence on their properties, since the grains absorb radiation and cool the gas. This makes the ionization front slower, especially if the density is low (117). The dust increases the compression in shocks (n8) and has an influence on the dynamics of clouds collisions. The conditions in shocks, on the contrary, are important for the growth and evaporation of grains (119, 120). The relative velocity of the dust and gas was also determined. Calculations of the gas resistance under different conditions and with different velocities of grains are given in (121). Gershberg and Sheglov (122) revealed with a Fabry-Perot interferometer fast internal km s-1 in NGC 6618, V ~ ± 25 km s-1 in NGC 6523 and V ~ ± 10 motions V ~ ± km s-1 in NGC 7000 (see also (123)). Sheglov revealed weak components with V up to ± 100 km s-1 in Omega and Orion (124). The origin of these movements is not clear yet, they may be connected with outbursts of supernovae in nebulae ( 122), but the necessary outburst frequency is too high. A similar method was developed by Flynn and Ring (125) for the Orion Nebula. The general character of internal motions was evaluated here (126).

so

The presence of dust in diffuse nebulae was examined on the basis of H f3 and continuum ratio (127). The light reflected by dust is present in all three nebulae studied, so that the disintegration of dust in H II regions and its repelling by radiation pressure are rather slow. The statistics of reflecting nebulae on Palomar Sky Survey was carried out by Dorschner and Gurtler (128, 129). They compared the dimensions of the nebulae with stellar spectra and with dimensions of H II regions around B-stars. Previous calculations of Stromgren's radii were overestimated, new ones were calculated. Cometary-like nebulae adjoin to the reflective ones. Hall showed that the polarizations of the variable nebula R Mon is chiefly radial, it increased with distance from the star and reaches as much as 34%· The colour along the axis first turns blue and then red (130). The spectra of cometary nebulae were investigated by Dibai and Esipov (131, 132). Usually it resembles the spectrum of the star but S 129 turned out to be a common gas nebula. The morphological features of this nebula may be explained by the focusing of the converged shock (133). Khachikjan and Parsamian showed that the polarization of NGC 2261 does not change for six years (134). They carried out the colourimetry of an anonimous nebula and came to the conclusion that its emission is not reflected light (135). There was compiled a list of 23 nebulae on Palomar Sky Survey (136). Vardanian (137) showed that the tails of cometary nebulae are parallel to the mean direction of the stellar polarization, i.e. their directions may be connected with the magnetic fields of the spiral arms. The fine filamentary structure of reflecting nebulae is apparently a sequence of the interchange instability, when the cloud without the field penetrates into the magnetic field of spiral arms (138). After the cloud disintegrates into the filaments, the field penetrates into them and fixes ions and especially charged grains. H II zone around the Sun was calculated on the basis of the emission spectrum of the Sun in the ultraviolet and X-region (139). Due to a weak absorption for the quanta of high energy the ionization decreases continuously. The size of the zone is several hundred of astronomical units. A similar value is found in (qo) where the electron concentration is inferred from La. observations. The cut-off of the spectrum of cosmic radio noise near 4-5 MHz confirmed the presence of the absorbing zone H II with the emission measure from 8 to 165 in different l {ql, 142). If it is not a cloud surrounding the Sun, then < Ne > in the galactic disk should be about o·1 cm-3 • However, the uniform distribution is quite improbable in this case. They are not common H II clouds, but more probable quasi-regular small-scale fluctuations of the gas between clouds.

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H II regions in the Magellanic Clouds were studied by Feast {I4J), Dickel {I44), Mathis {I45). Temperatures and densities, non-homogeneities, and masses were determined. The decrement of 30 Doradus gave the extinction. The abundance of He is the same as in galactic nebulae (145). Baade and Arp {I46) measured the positions of emission nebulae in M 31 which were used for drawing the pieces of arms (147). The catalogue of nebulae in M 33 {I48) and in three other galaxies {I49) is based on pictures in Ha. Sersic compiled a catalogue of 85 H II regions in NGC 300 {ISO). DISTRIBUTION AND PHYSICAL CONDITIONS IN INTERSTELLAR GAS. MOLECULES

The general distribution of gas in the galactic disk had been investigated before. Therefore now only separate features and details were investigated, more attention was paid to deviations from the average picture. Relations of hydrogen and associations were studied, statistical parameters of clouds were determined (on hydrogen and Ca II lines). A great progress was achieved in the investigation of clouds on intermediate and high latitudes. Some peculiarities found here have not been definitely explained yet. The temperature of the interstellar medium evaluated from radio observations depends on the kind of lines (emission or absorption) observed and on the distribution of the temperature in dense and rarefied clouds. The temperature itself largely depends on the presence of H 2 molecules. There are many papers with calculations of the abundance of these molecules, but there are no definite results yet. It may be concluded that the abundance of H 2 is relatively low in common clouds and high in dense globulae, but the total abundance in the disk hardly exceeds the abundance of atomic hydrogen. Methods of direct observations of H 2 ultraviolet lines are discussed. Among other molecules, especially interesting is OH, whose lines show extraordinary properties, which are qualitatively explained now as the result of stimulated emission (maser-effect) and sometimes as that of the presence of the magnetic field. The rotation curve of the Galaxy was redetermined from new observations by Shane and Bieger-Smith {ISI). They showed that this curve is systematically different for the Milky Way in the Northern and Southern Hemispheres. The analysis also indicates the presence of systematic streaming motions with velocities about 10 km s-1 and breadths of the order of 100 pes. This gives difficulties in the determination of the distribution of gas. Pronik analysed the published data of radio observations and showed that the rotation curves are not the same in regions with positive and negative latitudes {I52). Streams along the Sagittarius arm were found by Burton {ISJ). Lindblad has observed and analysed profiles 21 em in the anticentral region, represented there in terms of gaussian components {I54) and studied the structure and motions of the gas in this region {ISS)· Asymmetry of the velocity field on both sides of the galactic centre was confirmed by Kerr and Hindman {IS6). Using data on the cross-sections of the Galaxy in (r, z)-planes through the Sun, published earlier by W esterhout, van W oerden re-determined the general distribution of neutral hydrogen in the Galaxy {I57)· The thickness of the hydrogen layer increases markedly with increasing distance from the galactic centre, the amount of the neutral hydrogen in the Galaxy may be 5 to 7 x 109 solar masses. From the analysis of optical and radio data Pskovsky {IS8), and Pavlovskaya and Sharov {IS9) came to the conclusion that our Galaxy is probably a multi-arm rather than usual spiral. Gosachinsky {I6o) showed that far away from the centre in l = 10 to 40° hydrogen has the structure of sheets inclined to the Galactic plane. The cause of deviation of the disk from the plane was discussed by Elwert and Hablick {I6I). They think that the gravitational attraction of the Magellanic Clouds may have a resonance effect on the gas layer, which later on leads to the observed deviation.

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Smith (162) and Prata (163) found hydrogen concentrations with peculiarly high velocities. The nature of these objects is unclear, they may be similar to the gas complexes discussed in (164) which possibly are connected with the associations in Perseus. The distribution of HI in the region of the galactic anticentre and in the vicinity of super-nova remnant IC 443 (165), in the region of Taurus (166) was studied. A reverse correlation of absorption and of H I concentration was revealed in the latter paper so that in heavy clouds H 2 consists of 85% of the whole mass. Habing (167) revealed at the intermediate latitudes gas with velocities corresponding to those of the outer parts of the Galaxy. This gas may extend several kiloparsecs from the galactic plane; it may be a distorted part of a far arm. A connection of gas with stellar associations was studied for the associations Mon I and especially for Mon II. Raimond (168) found there condensations of HI with total mass of about 20 ooo M 0 • Such condensations had been mentioned before, for instance gas was found in the cluster NGC 2244 which is a part of Mon II (169). An expanding shell was also revealed around this association (170). But Bystrova, Gosachinsky and Ryzhkov (171) believe that there is neither a concentration of gas towards the association nor an expanding shell. They interpret the maximum of hydrogen emission as a bridge between two arms. Investigations of H I in other associations are carried out mainly in the Netherlands (172). Goldstein (173) showed that the total mass of HI in the globular cluster M 13 is less than 140 M 0 • The distribution of H II is determined from thermal radio emission (cf. Draft Report of Commission 40), as well as from the absorption of low-frequency cosmic radio noise (142). The ring of H II in the inner part of the Galaxy (3·5-4·5 kpcs) may also be revealed on the deficiency of HI (174). The motion of a star with Stromgren sphere through the gas forms a shock (175). Cloud structure and kinematics of the gas observed on intermediate latitudes, i.e. near the limits of the disk, were investigated by Takakubo (176) with the decomposition of the profiles into gaussian components (177). There was revealed a high correlation of the lowvelocity peak of H I and the main components of Ca II line, in spite of the difference in directions. The correlation of the secondary peak of H I profile and the high-velocity Ca II component is poor, indicating that high-velocity clouds are small in size. Clark (178) determined densities, masses and other parameters of the clouds from the absorption components in spectra of five bright radio sources. He found on the average 4 · 1 clouds per kpc in the galactic plane. There is no systematic deviation from pure rotation- the line in the spectrum of Sgr A is symmetrical about standard frequency. The layer of the clouds is very thin and dense, H I clouds were not observed in absorption on high latitudes. The different width of absorption and emission lines is due to the fact that absorption components are formed in cool clouds, while emission components-also in the hot rarefied gas between clouds; this gas is transparent due to its high temperature. A preliminary report on observations of optical lines for the comparison with radio observations is performed by van Woerden (179). The velocity dispersion of Ca II interstellar lines (6·9 km s-1) is less than that of young stars (180). The dependence of the intensities of Ca II lines on the distance from the stars was studied by Wilkens (181). Buscombe and Kennedy (182) summarized all published radial velocities of Ca II lines on the southern Sky, together with new observations and compared them with new distances of OB stars. Na I lines were also studied. Livingston and Lynds (183), and Hobbs (184) measured interstellar lines in the spectra of bright stars in particular ex Cyg, with very high wavelength resolution, and showed that there are much more components than usually are observed with lower resolution. A superfine structure was also observed in some clouds. It means that internal turbulent velocities are less than o,64 km s-1 (184). Smith (185) showed that when analysing profiles one should

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take into account the expansion of the clouds along the interstellar magnetic fields. The profile may be in such case with two peaks and will be interpreted as two clouds. Resonance interstellar absorption lines of 0 I, S II, Al III, C II in the region I26o-1720A were observed with rockets by Morton and Spitzer (186) in the spectra of o and 7T Sco. A comprehensive investigation of H I at high latitudes (b > + 40°) was carried out mainly by Dutch radioastronomers. A systematic survey resulted in the discovery of several new clouds approaching with high velocity (187). Blaauw and Tolbert (188) discussed the intermediate-velocity features up to ± 70 km s-1 • They suggested that an inflow of matter from I ~ 120°, b ~ + 15° penetrates close to the Sun. The total mass involved in disturbances is evaluated about 26oo M ®· The phenomenon is much more pronounced at the high negative velocities and is restricted to a smaller area on the sky. The high-velocity clouds were studied by Hulsbosch and Raimond (189). They determined for two clouds sizes of - 3~5 and 1~3 and masses of-2500 r 2 M® and 150 r 2 M®, where r is the distance to the clouds in kpcs. An investigation of high-velocity clouds near N and S galactic poles was carried out by Dieter (190). Two peaks with velocities -20 and -50 km s-1 are observed near the North pole. Masses and densities of the clouds are less than common ones. The picture in the southern hemisphere is similar, but there are no such definite streams as in the northern one. Some separate clouds with velocities up to -90 km s-1 were observed. The width of the lines corresponds to T ~ 150°, the velocity dispersion is about 2'5 km s-1 • Oort considered several possible interpretations of these phenomena ( 191): motions in the galactic corona, connected with explosions in the disk or with giant associations, the inflow of metagalactic gas into the Galaxy, and so on. However, the flux of the flowing matter should be too high in this case, and we expect a considerable influence of it on the dynamics of the gas in the galactic disk. Moreover, too high density of metagalatic matter is necessary for this explanation. A possible exchange of the gas between different parts of the disk and outbursts of the gas from the galactic layer were discussed. It is difficult to explain the formation of condensed clouds with a high density and fast internal motions. The possibility cannot be excluded that the clouds are near-by and are supernova remnants. But a comparison with the data on Ca II lines speaks in favour of larger distances. Shklovsky supposed that there is a maser-effect in clouds, which increases the black-body radiation on the line frequency. The inversion of HI atoms population may be created under some conditions with La. line from H II regions near the limits of the disk (192). The possibility of such inversion was studied by Varshalovich (193). The distribution of the mass of clouds p(M) ,..._, M-fl was calculated by Sheffler (194) from the distribution of the extinction. He found f3 ~ 2 for M < 5 x 103 M® and 1 to I'S for M > 5 x 103 M®. The mass of a common cloud is 20-30 M® and the diameter is about 3 pes. A general statistical model of clouds and of their transformation on the basis of former ideas by Oort and Spitzer was constructed by Field and Saslaw (195). They considered collisions of clouds, their confluence due to dissipative processes, gradual growth of the mass, formation of massive complexes. The appearance of young stars gives H II regions and the expanding shell of H I divided into little clouds run away from the complex. The calculations of the kinetics of this processes gave the spectrum of mass of clouds as M-3/ 2 in agreement with (194). Inelastic collisions of clouds were considered also in (196) and (197). The propagation of the shock wave, heating and cooling of the gas up to the standard external pressure, a possibility of gravitational instability in the compressed region were discussed in the latter paper. Shock waves with emission, were discussed by Kaplan and Klimishin (198). They take into account the non-stationary scattering of light and heating of the gas before the front. Numerical calculations of the structure of the waves with the emission in a partly ionized gas were done by Kaplan and Podstrigach (199). The structural function of the turbulence was inferred from the analysis of interstellar lines by Kaplan and Klimishin (zoo).

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Pikelner discussed general dynamics of clouds in the magnetic field of spiral arms (201). Common clouds are supported by the field. They have oscillations across the magnetic lines and the collisions in these directions are elastic. They move rather freely along the lines and the collisions are inelastic. The complexes grow, come down to the galactic plane and collect gas until the beginning of stars formation and flying away of the gas. The temperature in H I regions used to be determined from saturated emission lines which give the harmonic mean T ~ 125°. Shuter and Verschuur (202) separated absorption lines 21 em in the spectrum of radio sources into gaussian components, which they treat as thermal ones. The width of the components gives temperatures of clouds from 25 to 120° and Nn. The calculated harmonic mean temperature for all clouds and for 20% invisible clouds appears to be less than 70°. This value differs from the emission radio temperature, because the main contribution to the absorption gives cold clouds and the contribution to the emission gives, besides cold clouds, also hot clouds and the gas between clouds. Different harmonic temperatures for emission and absorption lines with some given distribution of H I are obtained also by Marx (203). An influence of the cloud structure on the measurements of the temperature and density with 21 em line was discussed by Rohlfs (204). The heating of the rarefied gas between the clouds in the absence of ultraviolet radiation may be performed by superthermal particles from 10 to 100 MeV (205). The radiation field in different parts of the Galaxy was calculated by Zimmermann (206) and Kaplan (207). The density of the energy is higher in the halo where interstellar absorption is ineffective (20']). Cooling of interstellar gas was reconsidered by Dalgarno and Rudge (2o8). They take into account excitations of C+ and Si+ in collisions with hydrogen atoms followed by spin exchange. The process appears from 3 to 5 times more effective than electronic collisions. The temperature depends markedly on the presence of H 2 molecules, which cool the gas effectively if T > 6o 0 • Cooling is a result of shock collisions o-2 and spontaneous transition 2-o. Transitions 2-1 and 1-o have insignificant probability (209). Transitions 2-0 give the line 28 p., which can be principally observed. Its intensity in the galactic plane should be comparable with B.(5o 0 ). The possibility of observations of ultraviolet Lyman line H 2 have been discussed by Spitzer, Dressler and Upson (:uo). The curve of growth oscillator strength and equivalent width were calculated when different concentrations of H 2 were present. Direct observations of H 2 have not been performed yet. The relative deficiency of H I in heavy absorbing clouds speaks in favour of the presence of molecules. For instance, there is relatively few HI in the cloud obscuring 'Omega' (211). The other method of evaluation is from the gravitational potential in the disk. Such estimates were done, for instance in (212), on the base of the comparison of velocities and Z-distribution of H I clouds and cepheids. The estimates gave for H 2 abundance of o·8 to H. However, the evolutional effect for cepheids (their age is comparable with the time of motions from the galactic plane) and magnetic forces for clouds were not taken into account. The origin of H 2 is usually connected with recombinations on the surface of an interstellar dust grain. Atoms are bound with the grain surface by van der Waals forces, i.e. by physical absorption. However in (212a) it was shown that due to zero-point energy, physical absorption of H atoms by grains with T > 8°K is negligible. The possibility of chemical absorption is not studied yet. In this connection the considerably less effective mechanism by Stecher and Williams (213) should be discussed. This mechanism is an outflow of H 2 from the atmospheres of cold giants and supergiants with stellar winds. Very strong interstellar CN lines were revealed in the group of stars situated in the emission nebula (214). Propagation of the ionization front in the cloud with a high concentration of

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dust resulted in the evaporation of grains and dissociation of molecules of the stream. In general, CN lines are observed in complexes abundant with dust. One of the levels of molecule CN is very close to the ground state (the difference of the energy corresponds to o·254 em). Shklovsky (:us), and Field and Hitchcock (216) pointed out independently that the population of this level is very sensitive to the density of cosmic radiation. The fine structure of CN absorption-line shows that the population of the second level corresponds to the temperature of exciting radiation about 3° (215, 217). This confirms the presence of black-body radiation in the Universe, as all other sources of radiation in interstellar space are much weaker. OH molecule radio lines of which .\ = 18 em were revealed in 1963 is especially interesting. Observations of these absorption lines in spectrum of Sag A showed some peculiarities (218, 219). The lines are very strong, wide and displaced relatively to the position, expected from the velocities of hydrogen features. Relative intensities of quadruplets do not correspond to the theoretical values. First, there were attempts to explain this by the effect of saturation (220}, but they were not a success. The distribution of OH in the vicinity of the galactic centrum is irregular, there are many clouds with different velocities, which are not in accordance with the velocities from 21 em line (221). It was an unexpected discovery that OH is observed in the emission (222) near large H II regions. The lines were very bright, the excitation temperature was more than 9°, i.e. much higher than that far from H II. One component of the quadruplet consisted of several very strong peaks with the width of about o·4 km s-1 that corresponds to an unexpectedly low temperature. Some other components of quadruplet were not observed at all. Similar peculiarities were observed in the Orion Nebula and in others. It was revealed further that the emission in some components is strongly lineary polarized and the value and direction are different for the clouds with different velocities (223). All these properties were confirmed and investigated in detail in many papers (see Draft Report of Commission 40). More than so% of all investigated H II regions show anomal OH emission. The size of the sources is usually less than 20" (Burke), several details show almost 100% circular polarization (Barrett). The interpretation of anormal intensity and of narrows of some components is connected with maser-effect. The excitation of upper levels may be due to ultraviolet emission of the surrounding H II regions (224}, with their Lrx. radiation (225a). According to (225) the maser-effect is connected with the infrared radiation of the hot pre-stellar bodies which contain OH molecules inside. Effects of polarization are connected with magnetic field. In different components maser-effect can be different and probably it is effective mainly along the magnetic field, giving circular, but not elliptic polarization (Ginzburg). The details of this process are not clear yet. There were some attempts to observe the ultraviolet absorption line of OH 308oA in the spectrum of 06 star (226). The line was absent and the upper limit of abundence of OH was 9 times less than may be expected from the radio data. Apparently OH is concentrated in small regions which are not projected on the star. Abundance of OH in the interstellar gas is determined mainly by exchange reactions with H 2 and other molecules at temperature of about 100o0 connected with shock waves (227). SUPERNOVAE REMNANTS, MAGNETIC FIELD OF THE GALAXY, DYNAMICS AND ORIGIN OF SPIRAL ARMS

Hogg (237) showed that the radio source IC 443 has a shell-like structure, coinciding with a region of optic brightness. He measured also radio radiation from a great number of other possible remnants of supernovae. Davies (238) investigated a part of a spur, visible from England, and showed that its outer edge is sharp and the spur itself is similar to Cygnus loop by its structure and brightness. Brosche (239) investigated the expanding of a shell of Crab Nebula by proper motions. He confirmed that the motion is accelerated. Heiles (240)

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investigated a shell expanding in interstellar gas. He showed that Shklovskii's automodel solution is true only as long as the temperature behind the front does not fall below Io7 °K. Mter this stage the emission of ions 0 VIII and others becomes essential. However in (240) the isothermicity of plasma behind the front is proved incorrectly. In the layers, near to the front, Coulomb interactions cannot establish the equi-partition. The electron temperature should be determined rather by different instabilities. Sheglov (241), discovered in NGC 6990 radiation of Fe x with intensity of 3-5 relays, proved experimentally the high electron temperature behind the front in Cygnus Loop. The influence of the magnetic field of the Galaxy on the expanding shells of supernovae was considered by scientists of the Princeton group (242, 243). They considered a case of a strong and weak field-the last one is closer to reality. The field is compressed strongly only near a shell-piston, and in the main part of interstellar gas, compressed by a wave, it is strengthened slightly. The instability of Rayleigh-Taylor takes place near the boundary, it explains the filamentary structure. The Crab Nebula is the most interesting supernova remnant. Here, radio emission is concentrated on the centre and it has not a shell structure. Shklovsky showed that, on the whole, relativistic electrons, but not protons, are generated in it, so such a nebulae cannot be a source of usual cosmic rays (244). Both the origin of relativistic particles in remnants and the formation of the magnetic field in it are left to be a problem, because a magnetic flux, for example that of the Crab Nebula, could not be taken from a star or interstellar medium. Kardashov (245) supposed that in the period of a stellar collapse a rotating instability occurs, a shell, connected with a star by a magnetic field, is separated, and the fast rotation of the central nucleus winds the lines of force. The rotation is maintained by compression and takes place till now. Observations show that for IO years the optical polarization of Crab Nebula has half decreased and that the nebula radiation has a component with an elliptic polarization (247). A checking of these wonderful results is very desirable. Westerlund and Mathewson (248) discovered in LMC three nebulae-remnants of supernovae of type II. Two of them and many associations are situated in the ring H 1 by a diameter of about I kpc-apparently it is a remnant of an explosion of a massive supernova of the first generation. The third remnant is in the other ring, containing associations and strong non-thermal source. The mass of a large shell is about 3 x 107 M®, therefore, the original mass is about Io5 M®, the age is about 3 million years with medium density of I cm-3 • Apparently, a series of superexplosions results in conditions for the formation of associations and individual stars. The interstellar polarization gives one of the methods of the investigation of the magnetic field. Martel (249) investigated a dependence of the polarization on a wavelength. Studying a correlation with the galactic longitude, Loden (250) investigated in great detail the polarization of accidentally selected stars in 19 regions of the sky. Serkowski (251, 252) determined a dependence of the polarization on longitude and investigated in detail a region including a cluster and association of Cyg VI. Dombrovski (253) found a region of homogeneous polarization in a district of the cluster NGC 1502. Pronik (254) compared the polarization with both the velocities of Ca II and the shape of dark nebulae. The field turned to be very irregular, often directed differently above and under the galactic plane, and in some parts it was not parallel to the galactic plane and not directed along the arms. Visvanathan (255) investigated 30 stars in LMC. The maximal polarization is o'!"o68 ; (pfAv)max = o·o7 on the average all over a cloud. The polarization plane does. not change in large regions. On the average, lines of force are parallel to the plane and to the structure of the nebula, forming a very flat disk. Zwicky (256) found in M 82 three types of polarization-common, along a plane, radial around some luminous spots and directed along filaments and light band, thrown out by an explosion.

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The polarization of non-thermal radiation gives information on a magnetic field of the Galaxy. Mathewson and Milne (257) found that regions of high polarization of radiophone coincide with that of weak Faraday rotation for distant radio sources, it is naturally explained by low depolarization on these places. They found that the direction of polarization, as a rule, lies in a band with width of 6o 0 relative to a big circle, passing through galactic poles and the equator point with l = 160°. It has been confirmed in (258) and indicates the presence of a sufficiently homogeneous field in the arm. The rotation of a polarization plane of extragalactic sources takes place, as it has been shown before, in the Galaxy, and the field is parallel to the galactic plane (259). However, the field structure is compound and does not correspond to a simple picture of a tube of parallel lines of force. However, the authors did not divide north and south latitudes, where a rotation has a different sign. Indeed, Morris and Berge (26o) showed that the rotation is carried out by lines of force, which are parallel in a middle of the arm, but have an opposite direction in the northern and southern hemispheres. Moreover, RM is 1·5 to 2 times as much in the S hemisphere than in the N. Gardner and Davies (261) made these results more precise and found that there is a third narrow region along the equator where the rotation is especially strong and has one sign. Bologna and others (262) investigated the depolarization of extragalactic sources. The polarization increases towards the equator and, therefore, it is determined by the Galaxy. The depolarization grows with the increase of an angular dimension of the source. These phenomena can be in principle explained if fluctuations which are less than o·3 pes and with Neil ~ 3 x 106 are superimposed on the general field. Maltby arrives at smaller dimensions (o·1 pes) and expresses his doubt that the depolarization is in the Galaxy (263). Such a doubt is expressed in (259), too. Measurements of Zeeman's effect in 21 em line (264, 265, 266) gave B ~ (5-7 x 10-6 G in the cloud, but this result depended on the adopted direction of the complete vector B. The obtained data of observations do not yet allow to construct a picture of the field, but they exclude some simple models proposed before. Stctpien (267) and Hornby (268) consider that observations are presented best by lines of force which form (inside the arm) a spiral, stretched by the differential rotation, thus the plane of spires form with an axis of the arm an acute angle. Woltjer (269) considered the field as consisting of weak quasi-homogeneous (Blater 5 x 10-6 G) (Symposium no. 31), on which thestrongchaoticfield are superimposed. The lines of force of this field are parallel to the axis of the arm, but changing the sign at a distance of about o·I pes. This little scale is necessary for the explanation of a regular distribution of the rotation measure with the position on the sky. It is supposed that the field has no dynamic meaning on the gas. Using this picture, Wentzel (270) applied Petchek's mechanism to the interstellar gas- the compression of gas between the regions of the opposite fields and ejection of compact clouds from there. However Pikelner (201) points out a number of dynamic difficulties in the picture of the strong irregular field. Besides that, the explanation of the rotation of the polarization plane in the presence of small irregularities needs improbably high electronic concentration, if gas is neutral in the main. As a whole, the problem should be additionally investigated- both by observation and theoretically. The problem of the origin and existence of spiral arms is of great interest. The gravitation theory is widely used. Small disturbances in the gas of gravitating stars are considered (271). The density fluctuations propagate as a heavy sound. The field of these fluctuations attracts stars with low velocity dispersion and the gas fluctuations can have a spiral form under certain conditions. By the gas compression the field in it takes a prolonged orientation. The arms are not wound, because perturbations move relative to stars. The investigation of perturbations in a rotating disk, its stability, axis-symmetric oscillations was carried out in many papers (272,

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273, 274, 275, 276). The gas flows into the arm on the one side, on the back one it flows out. True, it is not proved yet whether this process could take place in the non-linear approximation, when the gas density is comparable to or exceeds the stellar density of the background. The decay and formation of arms and indirect influence of the field on the relaxation of star velocities in linear approximation are considered in (277, 278). Pikelner (138) considered another model, where the field has a definite dynamic role. It explains the thickness of arms in different galaxies and at different distances from the centres, allows to understand the opposite direction of lines of force and explain a number of other peculiarities. However, this theory, as others, which consider the arm as a conservative formation, cannot explain a persistence of the spiral shape. Probably, there should be a synthesis of both points of view, where the field plays an essential dynamic role, but the gas flows through the arm. Richter and Wallis (279) supposed that, in the Galaxy, the gas forms rings, not spread out by the differential rotation, and arms are formed by crossing these rings with fronts of shock waves, originated from explosions in the centre. Now the formation of the field of arms is usually connected with a condensation of metagalactic field together with the gas when forming of the Galaxy. Piddington (28o) showed that the strength of the magnetic field in the disk depends considerably on the relative orientation of the primary field and rotation axis. Barred spirals are also considered within the limits of the gravitating theory (281, 282, 283), the angular momentum of individual stars is not constant in this scheme because of the attraction of a bar, and streams in the outer directions appear. However, the stability of the system is not proved and, in general, the whole scheme needs artificial suppositions and special initial conditions. Pikelner (284) supposed that in SB, especially in SBc, there is an almost homogeneous sphere of old stars, in the field of which the rotation is rigid body. Such a sphere is formed as the result of the explosion which has taken place in the Galaxy at the very early stage of its formation. Streams along the bar, condensations on its ends, the transition of the bar into spiral arms, etc. are explained within the limits of this scheme. The accretion of intergalactic gas, flowing into the Galaxy and winding can form in principle a spiral arm (285). However, this hardly explains the symmetry and regular structure of the arms. The formation of bridges between interacting galaxies and tails is discussed in (284, 286, 287). Zasov (288) supposed that intergalactic gas flows to bridges, penetrates into them and then falls to galaxies. The statistics of distortions of gaseous layers of galaxies (it is often in small close groups) are given in (288). THE INTERACTION OF THE GAS WITH COSMIC RAYS. INTERGALACTIC GAS, GAS IN QUASI-STELLAR SOURCES

The interaction of cosmic rays with interstellar medium becomes apparent not only in nuclear collisions and in collisions with moving magnetizing clouds, but also in the interaction with plasma waves which should always be present in the gas with microscopic motions. It was investigated in detail for different conditions by Tsitovitch (see a review ('2.89)), a possibility of the acceleration of relativistic particles was determined. Ginzburg (2898) showed that the interaction with plasma waves explained the isotropy of cosmic rays. Parker (290) supposed that the formation of the galactic corona can be connected with the instability of the gas with the field, retaining cosmic rays. The existence of the metagalactic gas is inferred sometimes from cosmological considerations, according to the value of critical density, necessary for the noticeable slow-down of the metagalaxy expansion. However, such a slow-down has only been proved indefinitely so far, that is why direct observations of the gas is very important. Kowal (291) has discovered dark

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spots on the background of three galaxies, but they are smaller than galaxies and in two cases they are connected with the galactic structure, that is why they cannot be considered as metagalactic. Gunn and Peterson (292) investigated a weak depression in the spectrum of the distant quasars 3C 9 beginning from Lrx. It corresponds to nH ~ 6 x 10-11 cm-3 at this distance, it is considerably smaller than the critical density even taking into consideration the ionization when T = 2 x 106 • However, such an estimate depends strongly on the extrapolation of the continuous spectrum, and the latest data indicate that absorption is somewhat smaller. Bahcall and Salpeter (293) indicated that if gas is concentrated in clusters, lines but not depressions should be in the spectrum of quasars. The absence of H 2 uo8A line means that the abundance of molecular hydrogen is small and, apparently, the intergalactic gas is ionized completely. The absence of H 2 is shown in (294), too. The low concentration of atomic hydrogen follows also from measurements of 21 em line from Cyg A and Vir AT < o·oo1 and o·o2 correspondingly. In the second case it means that hydrogen does not absorb also in this galaxy itself- the spin temperature is high because of the strong radiation and the gas is transparent (295). The ionization of hydrogen can be connected only with high kinetic temperature. The temperature conditions of metagalactic hydrogen was discussed by Ginzburg and Ozernoy (296). They took into account the emission of hydrogen and cooling due to the general expanding of gas, not being a part of clusters of galaxies. Heating is produced by cosmic and sub-cosmic rays, the existence of which is probable in the rarefied gas. Explosions of radiogalaxies give the directed streams of relativistic particles, which generate plasma waves, heating the gas. This mechanism is especially effective in clusters. In the result of it the temperature in a cluster depends on the history of the given gas, and between the clusters the temperature, apparently, is about 105 or somewhat higher. A similar calculation, taking into account helium, but without the general expanding, was carried out by Gould and Ramsay (297). The upper limit of the temperature of the intergalactic gas when n ~ 10-5 cm-3 is determined by the absence of the noticeable background of X-rays. Different mechanisms of production of X- and y rays in the Galaxy and Metagalaxy are discussed by Ginzburg and Syrovatski (2()8), Tucker and Gold (299) (see in detail Commission 44). Modern measurements of X-rays give the upper limit of T < 3 x 106 (300). The absence of the background of X-radiation shows also that the quantity of relativistic electrons is considerably smaller in the Metagalaxy than in the Galaxy, otherwise there should be a strong inverse Comptoneffect for photons of the relict black-body radiation (301). This fact and the existence of black-body radiation itself, exclude steady state cosmology. Black-body radiation was discovered at centimeter waves in 1965 (302, 303). Its spectrum and the energy density correspond to T = J°K. It is a remnant of the black-body radiation of high temperature at the initial period of the Universe expansion (304). From the theory of the hot Universe it follows, that about 10% of He atoms should be in the primordial gas. The possibility of observations of He3 in metagalactic and interstellar gas is discussed by Sunyayev (305). Emission lines of different ions are observed in quasars (3o6, 307, 308, 309). The analysis shows that it is a shell with a standard chemical composition and possible filamentary structure, surrounding the nucleus of quasars and expanding with the velocity of about 1000 km s-1 • Both the conditions of ionization and excitation and the gas temperature are studied, but here there are yet many indefinite parameters (310, 2II, 312, 313), in particular, conditions of excitation. The ultra-violet part of the spectrum of synchroton radiation is calculated on the basis of the optic part by Greenstein (314). The absorption lines of expanding shells are observed in some quasars (315, 316). Dibai, Pronik, Esipov carried out the spectrophotometry of nuclei of Seyfert galaxies with strong emission lines, calculated physical conditions in gas, discussed the probable mechanisms Q2

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of excitation (317, 318, 319). Besides that, they analysed spectra of quasi-stellar sources (320, 321), estimated the mass of the gas. GRAVITATIONAL CONDENSATION, FORMATION OF STARS AND GALAXIES

The general theoretical consideration of the gravitational instability of the non-uniform medium was carried out by Ozernoy (322) and Simon (323). The influence of the magnetic field, when the compression occurs along lines of force or independently, is estimated in (324). In the first case the critical mass is two times less. The thermal condition during a protostar compression, escape of energy in H 2 lines, the role of H 2 dissociation are considered by Gould (325). When n < 100 cm-3 and T ~ 100° compression turns into free fall, in spite of the possible heating by fast particles and turbulence (325). When n > 100 cm-3 superelastic collisions decrease cooling and compression becomes slower, turning into oscillations (326). McNally (327) took into consideration that the centre of a cloud (from which a cluster forms) is more dense. It cools quicker, that is why a compression occurs there also quicker and a dense nucleus forms. In protoclusters with M < 104M® the central temperature is only about 100°, cooling occurs slower, and no nucleus forms. The thermal instability is possible on scales smaller than the critical Jeans' length. Field (328) takes into account the sound velocity, heat conductivity, magnetic field, rotation, external gravitational field; and Hunter, the gravitation of fluctuations themselves (329). Such an instability can give condensations in nebulae, the solar corona and partly facilitate the formation of galaxies. But it is effective only in special conditions, that is why its role in the formation of stars and galaxies is hardly considerable. Condensations in nebulae are also formes not due to thermal instability (330 ). The compression of a cloud, when there is an external pressure, can be not quasistatic, but with the formation of a cumulative shock wave, forming a region of high pressure in the centre of a cloud (331). It facilitates the stellar formation in the centres of globules, submerged into nebulae. The formation of pre-stellar bodies in a cloud, compressed by a shock wave, is calculated also by Kossatsky (332). Massive clouds fragments during compression. This process was considered on a simple model when p = o for different types of disturbances (333). The statistics of fragments according to masses allow to explain the function of stellar masses (besides massive stars) in clusters (334). The integration of fragments is taken into consideration in (335). Grzedzielski (336) examined the fragmentation of protogalaxy with large dispersion of internal velocities. Besides the condensation of globules, the appearance of young stars in old clusters can be connected with the accretion of gas by stars (337). Earlier, this idea was expressed by Lebedinsky. As the result of condensation of globules or accretion non-stationary red dwarfs and Herbig-Haro objects are formed with small mass. Schatzman and Magnan (338) supposed that the excitation of these objects is produced by protons of high energy and Lortet-Zuckermann estimated the emission of the interstellar matter in the neighbourhood of flare stars (339). The dense stellar nuclei of galaxies lose stars and compress until the collisions of stars would be essential (340, 341). The gas appears, it compresses in a thin disk, and stars form again (342). This may result in a marked luminosity increase. A number of review papers, covering the investigations of Japanese scientists in this field (carried out in the main till 1964) is included in the collection 'The structure and evolution of galaxies'. The evolution of galaxies, radiogalaxy, the formation of spiral arms and dynamic model of barred galaxies, explosions of galactic nuclei, the stability of spiral arms are included in this review.

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Lynden-Bell (343) considered the large-scale instabilities, appearing during the collapse of the rotating self-gravitating spheroid without internal pressure. The formation of the bar distributed along the diameter is possible in this process. From the other point of view the formation of bar and spiral arms can also be connected with the fact that the gravitating condensation compresses the field at first in the central, more dense, nucleus, and magnetic forces give the initial disturbance and stimulate the condensation of the gas situated along the tube of lines of force (138, 284). The discovery of the black-body relict radiation allows to make a considerable progress in the understanding of the early stage of the formation of galactic clusters. The conception of Jeans' instability raises a question on the initial equilibrium state, which could not be the state one. Peebles showed that in the hot expanding Universe the gas was connected at first with the radiation by way of a friction. Condensations could not compress because the radiation pressure prevented it (344). Osernoy (345) considered in detail the development of these instabilities, their temperature condition, the radiation output in the period of gas-recombination, the influence of different mechanisms of heating and cooling of the gas at different stages of the compression and fragmentation. Zeldovich, Novikov and Doroshkevich (346, 347) investigating the same problem, have shown that during the gasrecombinations the density is still so large that fragments with M ~ 106 M 0 are formed, i.e. still not clusters of galaxies. The energy resulting from the condensation of the first fragments, which may be quasars, heats the gas and prevents the condensation of other fragments. This energy creates conditions when the large masses of the galactic clusters type can be condensed. S. B. PIKELNER

President of the Commission BIBLIOGRAPHY I.

2. 3· 4· 5· 6. 7· 8. 9· 10. II.

12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

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COMMISSION 34 Flynn, E. H. 1965, Mon. Not. R. astr. Soc., I30, 9· O'Dell, C. R., Hubbard, W. B., Peimbert, M. 1966, Astrophys. J., I43t 743· Dorschner, J., GUrtler, J, 1966, Astr. Nachr., 289, 57· Dorschner, J. Astr. Nachr., in press. Hall, R. C. 1964, Astrophys. J., I39, 759· Dibai, A. E., Esipov, V. F. 1965, Astr. Zu., 42, 281. Dibai, E. A. 1966, Astr. Zu., 43, 903. Dibai, E. A. 1966, Astr. Zu., 43, 52. Khachikjan, E. E., Parsamian, E. S. 1964, Soob!c. Bjurak. Obs., 3S, 71. Khachikjan, E. E., Parsamian, E. S. 1965, Astrojizika, I, 417. Parsamian, E. S. 196s, lzv. Akad. Nauk Armjan. SSR, I8, no. 2. Vardanian, R. A. 196s, Astrofizika, I. Pikelner, S. B. 196s, Astr. Zu., 42, SIS. Williams, R. E. 196s, Astr. J., I42, 314. Lenchek, A. M. 1964, Ann. Astrophys., 27, 219. Alexander, J. K., Stone, R. G. 1965, Astrophys. J., I42, 1327. Ellis, G. R. A., Hamilton, P. A. 1966, Astrophys.J., I43, 227; I46, 78. Feast, M. W. 1964, Mon. Not. R. astr. Soc., I27, 19s; I28, 327. Dickel, H. R. 196s, Astrophys. J., I4I, 1306. Mathis, J, S. 1965, Publ. astr. Soc. Pacij., 77, 189. Baade, W., Arp, H. 1964, Astrophys. J., I39, 1027. Arp, H. 1964, Astrophys. J., I39, I04S· Courtes, G., Gruvellier, P. 196s, Ann. Astrophys., 28, 683. Veron, P., Souvayre, A. 196s, Ann. Astrophys., 28, 698. Sersic, J. L. 1966, Z. Astrophys., 64. 212. Shane, W. W., Bieger-Smith, G. P. 1966, Bull. astr. Inst. Netherl., IS, 263. Pronik, I. I. 196s, Astr. Zu., 42, 923. Burton, W. B. 1966, Bull. astr. lnst. Netherl., I8, 247· Lindblad, P. 0. 1966, Bull. astr. lnst. Netherl. Suppl., I, 77, 177. Lindblad, P. 0. 1966, Bull. astr. lnst. Netherl., in press. Kerr, F.]., Hindman, J. v. 1966, in Symposium on Radio and Optical Studies of the Galaxy, Mt Stromlo, Australia. Van Woerden, H. 1967, Bull. astr. lnst. Netherl., in press. Pskovsky, Y. P. 1965, Astr. Zu., 42, 1184. Pavlovskaya, E. D., Sharov, A. S. 1966, Astr. Zu., 43, 40. Gosachinsky, I. V. 1966, Astr. Zu., 43, 284. Elwert, G., Hablick, D. 1965, Z. Astrophys., 6I, 273· Smith, G. P. 1963, Bull. astr. lnst. Netherl., I7, 203. Prata, S. W. 1964, Bull. astr. Inst. Netherl., I7, Sll. Van Woerden, H., Hack, M., Blaauw, A. 1967, Bull. astr. Inst. Netherl., in press. Locke, J. L., Galt, J, A., Costain, C. H. 1964, Astrophys.J., I39, 1066, 1071. Garzoli, S. L., Varsavsky, C. M. 1966, Astrophys. J., I4S. 79· Habing, H. J, 1966, Bull. astr. Inst. Netherl., I8, 323. Raimond, E. 1966, Bull. astr. Inst. Netherl., I8, 191; Ibid. Suppl., I, 33· Davies, R. D., Tovmassian, H. M. 1963, Mon. Not. R. astr. Soc., I27, 4S, 61. Girnstein, H. G., Rohlfs, K. 1964, Z. Astrophys., S9t 83. Bystrova, N. V., Gosachinsky, I. V., Ryzhkov, N. F. 1966, Izv. glav. astr. Obs. Pulkove, 24, 130. Kaper, H. G., Smits, D. W., Schwarz, U. J., Takakubo, K., Van Woerden, H. Bull. astr. Inst. Netherl., in press. Goldstein, S. J, 1964, Astrophys. J., :140, 802. Rasiwala, M. 196s, C. r. Acad. Sci., Paris, 26I, 3291, 37SS· Ariskin, V. I. 1965, Astr. Zu., 42, 939· Takakubo, K. 1967, Bull. astr. Inst. Netherl., :19, 12S. Takakubo, K., Van Woerden, H. 1966, Bull. astr. Inst. Netherl., I8, 488. Clark, B. G. 196s, Astrophys. J., I42, 1398.

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I79· Van Woerden, H. 1964, A. Rep. Mt Wilson and Palomar Obs., Carnegie Inst. Year Book, 63, 23. ISO. Feast, M. W., Shuttleworth, M. 196s, Mon. Not. R. astr. Soc., I30, 24S· ISI. Wilkens, H. 196s, La Plata, Ser. Circ. no. 17. IS2. Buscombe, W., Kennedy, P.M. 1966, Mt Stromlo Mimeogram no. 9; Publ. astr. Soc. Pacij., 7S. IS3. Livingston, W. C., Lynds, C. R. 1964, Astrophys. J., 140, 818. I84. Hobbs, L. M. 196s, Astrophys. J., I42, x6o. ISS. Smith, A. 1964, Mon. Not. R. astr. Soc., I27, 347· 1966, Astrophys. J., I44, 1. IS6. Morton, D. C., Spitzer, L. IS7. Muller, C. A., Raimond, E., Schwarz, U. J., Tolbert, C. R. 1966, Bull. astr. Inst. Nether[. Suppl., I, 213. ISS. Blaauw, A., Tolbert, C. R. 1966, Bull. astr. Inst. Nether[., IS, 40s. IS9. Hulsbosch, A. N. M., Raimond, E. 1966, Bull. astr. Inst. Nether[., IS, 413. 196s, Astr. J., 70, ss2. I90. Dieter, N. H. I9I. Oort, J. H. 1966, Bull. astr. Inst. Nether[., IS, 421. I92. Shklovsky, I. S. 1967, Astr. Zu., 44· I93· Varshalovich, D. A. 196s, Astr. Zu., 42, SS7; 1966, Zu. eksp. teor. Fiz. Lett., 4, x8o; Zu. eksp. teor. Fiz., no. 1. I94· Scheffler, H. 1966, Z. Astrophys., in press. I96s, Astrophys. J., I42, s68. I95· Field, G. B., Saslaw, W. c. 196s, Publ. astr. Soc. Japan, I7, 38s. I96. Kogure, T. I97· Zimmerman, H. 1967, Astr. Nachr.; 1966, Proc. of 14. Int. Astr. Symp., Liege. 1964, Astr. Zu., 4I, 6S7· I9S. Kaplan, S. A., Klimishin, I. A. 196s, Astr. Zu., 42, SS2. I99· Kaplan, S. A., Podstrigach, T. S. 200. Kaplan, S. A., Klimishin, I. A. 1964, Astr. Zu., 4I 1 274. 20I. Pikelner, S. B. 1967, Astr. Zu., 44, in press. 202. Shuter, W. L. H., Verschuur, G. L. 1964, Mon. Not. R. astr. Soc., 127, 387. 203. Marx, S. 196s, Astr. Nachr., 2SS, ISS· 204. Rohlfs, K. 1966, Z. Astrophys., 63, 207. 1964, Joint Inst. Lab. Astrophys. Publ., no. 19. 205. Takayanagi, K. 2o6. Zimmermann, H. 1964, Astr. Nachr., 2SS, 9S· 207. Kaplan, S. A. 196s, in Dynamika Zvezdnykh Sistem i Fyzika Gazovykh Tumannostej, Alma-Ata, U.S.S.R. 20S. Dalgarno, A., Rudge, M. R. H. 1964, Astrophys. J., 140, 8oo. 1964, Astrophys. J., I39, 1004. 209. Raich, J. C., Good, R. H., Jr. 2IO, Spitzer, L., Dressler, K., Upson, W. L. 1964, Publ. astr. Soc. Pacij., 76, 387. 2II. Gosachinsky, I. V. 1965, Astr. Zu., 42, 929. 2I2. Dorschner, ]., Gurtler,}., Schmidt, K. H. 196s, Astr. Nachr., 288, 149. 2I2a. Knaap, H. F. P., van den Meijdenberg, C. J. N., Beenakker, J. J, M., Van de Hulst, H. C. 1966, Bull. astr. Inst. Netherl., IS, 2s6. 2I3. Stecher, T. P., Williams, D. A. 1966, Pub!. astr. Soc. Pacij., 78, 76. 2I4· Munch, G. 1964, Astrophys. J., 140, 107. 1966, Astr. Cirk., SSSR, no. 364. 2IS. Shklovsky, I. S. 2I6. Field, G. B., Hitchcock, J. L. 1966, Phys. Rev. Lett., I6, 817. 2I7. Field, G. B., Herbig, G., Hitchcock, J. L. 1966, Astrophys. J. 2IS. Robinson, B. J., Gardner, F. F., Van Damme, K. J., Bolton, J. G. 1964, Nature, 202, 989. 2I9. Goldstein, S. J., Gundermann, E. J., Penzias, A. A., Lilley, A. E. 1964, Nature, 203, 6s. 220. McGee, R. X., Robinson, B. J., Gardner, F. F., Bolton, J, G. 196s, Nature, 20S, 1193· 22I. Bolton, J, G., Gardner, F. F., McGee, R. X., Robinson, B. J. 1964, Nature, 204, 30. 196s, Nature, 20S, 29. 222. Weaver, H. F., Williams, D. R. W., Dieter, N. H., Lum, W. T. 196s, Nature, 223. Weinreb, S., Meeks, M. I., Carter, J. C., Barrett, A. H., Rogers, A. G. E. 20S, 440. 224. Perkins, F., Gold, T., Salpeter, E. E. 1966, Astrophys. J., I45, 361.

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:us. Shklovsky, I. S. 1966, Astr. Circ., USSR, no. 372. 22sa. Cook, A. H. 1966, Nature, 2IO, 6u. 226. Goss, M. M., Spinrad, H. 1966, Astrophys. J., I43o 989. 227. Carroll, T. 0., Salpeter, E. E. 1966, Astrophys. J., I43o 609. 228. Nguen-Hun-Doan 1965, C. r. Acad. Sci., Paris, 260, 2715. 229. Stoeckly, R., Dressler, K. 1964, Astrophys. J., IJ9o 240. 230. Hanasz, J. 1965, Acta Astr., IS, 31. 23I. Romashin, G. S. 1965, Trudy astr. Obs. Leningr. Univ., 22, 104; 1966, 23. 232. Hutchings, J. B. 1966, Mon. Not. R. astr. Soc., I3I, 299· 233· Malville, J. M. 1964, Astrophys.J., I39, 198. 234· Herzberg, G. 1966, in IAU Symposium no. 31, Radio Astronomy and the Galactic System, Noordwijk, Netherlands, in press. 23S· Roberts, M. S. 1966, Astrophys. J., I44, 639. 236. Gottesman, S. T., Davies, R. D., Reddish, V. C. 1966, Mon. Not. R. astr. Soc., I33o 359· 236a. McGee, R. X., Milton, J. A. 1966, Austr. J. Phys. Astrophys. Suppl., no. 2. 237· Hogg, D. E. 1966, Astrophys. J., I44, 819. 238. Davies, R. D. 1964, Mon. Not. R. astr. Soc., 128, 173. 239· Brosche, P. 1966, Z. Astrophys., 64. I. 240. Heiles, C. 1964, Astrophys. J., I40, 470. 24I. Sheglov, P. V. 1967, Astr. Zu., 44, in press. 242. Bernstein, I. B., Kulsrud, R. M. 1965, Astrophys. J., I420 479· 243· Kurlsrud, R. M., Bernstein, I. B., Kruskal, M., Fanucci, ]., Ness, N. 1965, Astrophys. J., I42, 491. 244· Shklovsky, I. S. 1966, Astr. Zu., 43, 10. 24S· Kardashov, N. S. 1964, Astr. Zu., 4I 0 8o7. 246. Khachikian, E. E., Berngen, F. 1966, Astr. Nachr. 247· Michelkin, E. G., Jacusheva, K. G. 1966, Dokl. Akad. Nauk SSSR, I68, 304; Astr. Zu., 43, 543· 248. Westerlund, B. E., Mathewson, D. S. 1966, Mon. Not. R. astr. Soc., IJI, 371. 249· Martel, L., Martel, M.-Th. 1964, Ann. Astrophys., 27, 203. 2so. Loden, L. 0. 1965, Stockholm Obs. Ann., 22, no. 8. 2SI. Serkowski, K. 1965, Acta Astr., IS, 78. 252. Serkowski, K. 1965, Astrophys. J., I4I 0 1340. 253· Dombrovski, V. A., Gagen-Torn, V. A. 1964, Trudy astr. Obs. Leningr. Univ., 20, 75· 254· Pronik, I. I. 1966, Astr. Zu., 43, 291. 25S· Visvanathan, N. 1966, Mon. Not. R. astr. Soc., IJ2, 423. 256. Zwicky, F. 1964, Astrophys. J., IJ9, 1394. 257· Mathewson, D. S., Milne, D. E. 1965, Austr. J. Phys., I8, 635. 258. Mathewson, D. S., Broten, N. W., Cole, D. J. 1966, Austr. J. Phys., I9, 93· 259· Seielstad, G. A., Morris, D., Radhakrishnan, V. 1964, Astrophys. J., I40, 53· 260. Morris, D., Berge, G. L. 1964, Astrophys. J., IJ9, 1388. 26I. Gar 3 for M type supergiants and the cluster diameter value of R = s·6 in Perseus. Similar agreement has been found in Cepheus. In any case a wide variety of values of R have been obtained with a value of R = 3 appearing to be an approximate lower bound. Further discussion of this question of the variability of extinction laws in the giving rise to values of R from 3 (in most regions) to 7 (in the Orion nebula region) has been given by Borgman (24). Observations of interstellar reddening in Cygnus and Perseus have been made by Nandy (25, 26, 27). The results are based on spectrophotometric measurements of 0 and early B type stars using spectra taken with the Schmidt telescope of the Royal Observatory in conjunction with an objective prism. In both regions the mean reddening curve can be represented by two straight lines which intersect near A. 43ooA but the ratio of the slope of the ultraviolet part is smaller by 30% in Perseus than that in Cygnus. Schalen (28) discussed the method of using spectrophotometric measurements of objective prism plates for making detailed studies of the wavelength dependence of interstellar absorption.

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Underhill and Walker (29) compared the measured spectral intensity distribution for 0 stars with those from model atmosphere calculations and found that the mean extinction curve showed a slope discontinuity at ~ 4445 A. Whiteoak (30) used a photoelectric spectrum scanner to find wavelength dependence of extinction at 30 wavelengths in the spectral region 3448A < A ~ IO 5ooA. Stars in Perseus, Monoceros, Cygnus and Cepheus were investigated. Perseus and Cepheus are similar. Stars inside and outside the Orion nebula give the usual difference in reddening. Monoceros lies between Orion and the others. No correlation of variation with galactic structure was found. Guthrie and Nandy (31) combine their extinction results with those of Mendoza (32) to arrive at a mean extinction law in the Pleiades, similar to that in Cygnus. They found a value of R = 3·3 as against the value R = 4·2 given by Mendoza. In any case the value of R is greater than the average as might be expected in the regions of hot stars. Wampler (33) discussed the curvature (or lack of curvature) of the reddening line in the UBV color-color plot. Becker (34) showed that in studying the color magnitude diagrams of clusters and associations the value of R = AfE 40 M®. According to Meggitt (36), the contraction time increases again when (M/M®) > 32. Penston (37) has shown that the observations of NGC6530 and NGC2364 are compatible with Hayashi's theory. McCrea (38) has attempted to explain the stars above the turn off points in some clusters in terms of mass exchange between the components of a close binary while Williams (39) and Dorschner et al. (40) attempt to account for their existence in terms of accretion. Schatzman (41, 42) has studied the influence of a rapid rotation coupled with magnetic activity on stellar contraction. Penston (43) has suggested an interpretation of the Neugebauer-Martz-Leighton objects as stars in formation dissipating their excess angular momentum.

Main-sequence Main sequence models are computed essentially in view of testing the influence of various parameters. According to Morris and Demarque (44) models with X= o·63 and Z = o·o3 are in good agreement with the observations. Mrs Massevitch and her associates have shown (45, 46, 47) that the homogeneous models on the main sequence are quite sensitive to the initial chemical composition. The results have also been compared with observational data (48) and the possible sources of disagreement, discussed (49, so). For masses M < 2·5 M®, the external convective zone is not deep enough, according to Tutukov (51), to allow enough depletion of LF to account for Herbig's observations (52).

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We may also report studies of the effects on models around the mid-main-sequence of different factors such as opacity and isotopic abundances (53, 54), of the generation of energy outside the convective core (55), of the pressure of radiation (56), of the bound-bound transitions (57), of the central convection on energy generation (58). Boury (59) has shown that a variable scattering opacity modifies appreciably the models of massive stars. A comparison (6o, 61) between models computed following Henyey's method (relaxation) and ordinary models shows satisfactory agreement although the first method seems to be more sensitive to the number of mass shells adopted. Detailed models forM= 1·48 M 0 (61), o·6 M 0 (53), o·27 M 0 (Kr 6o A) and o·16 M 0 (Kr 6o B) (63) have also been constructed. Post main-sequence evolution

Stothers (64, 65, 66) has followed the evolution of a 30 M 0 star of Population I up to the point where He is exhausted at the centre. He has also discussed (67) the development of semiconvective zones in stars with masses between 45 and 1000 M 0 as they burn their hydrogen. Evolutionary sequences covering about the same interval have also been constructed by Kotok {68-']2) forM= 15·6, 20 and 30 M 0 • The relative contributions of the different energy sources during these phases have been compared (73). Van der Borght (74) has studied the phase of hydrogen burning in heavy mass stars (40, 6o, 70, 120 M 0 ) composed initially of pure hydrogen. Iben (75-'78) has followed in great detail the evolution of Population I stars with masses 3, 5, 9 and 15 M 0 up to the exhaustion of He at the centre taking into account all the possible nuclear reactions. He has also pushed the evolutions of I, 1·25 and 1·5 M 0 stars up to the red giant stage (79). Evolution through the carbon flash has been studied by Kippenhahn et al. (So, 81) neglecting the neutrino emission. In taking the latter into account, Weigert (82) has encountered 'thermal' instabilities when He burns in a shell. Hofmeister (83, 84) has followed the evolution of 5, 7 and 9 M 0 stars up to and through the He burning phases for X = o·6o2, Z = o·o44 and X= 0·739, Z = o·o21. She finds that the loops of the evolutionary paths in the HR diagram during He-burning are very sensitive to the initial chemical composition. According to Dluzhnevskaya (85) and Varskowsky (86), the comparison between the number of stars observed and the number predicted by theory reveals a serious lack of agreement in the Hertzsprung-gap. The situation improves if the evolutionary loops are removed but agreement could also be obtained by using a variable initial luminosity function. The models so constructed have been used (87, 88, 89) to deduce some properties of the {3 Cephei stars (X~ o·7, M ~ 4·5 M 0 ; life-time ~ 1·5 106 years). It was also found (90, 91), in comparing ordinary models and those given by Henyey's method that a divergence sets in after H-burning in the centre affecting the shape of the evolutionary loops in the HR diagram. Hydrogen burning has also been the object of a variety of other papers (92-98). Reiz et al. (98) find that, for stars of spectral type later than about A7, age determinations could be significant only after the location of the zero-age main sequence has been fixed taking variations in initial chemical composition into account. Solar models and solar evolution have been studied (99, 100) especially to determine the neutrinic luminosity (101, 102, 103) of the Sun in view of its possible detection by appropriate observations (104). The helium flash has been studied in detail by Harm and Schwarzschild (105) and by Thomas (106, 107) for a 1·3 M 0 star of population II. Thomas shows that, if energy losses by neutrinos are taken into account, He-burning starts in a shell around the centre. In general, it appears that the flash is much less violent than anticipated and does not lead to a mixing of

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the envelope into regions where nuclear reactions can take place. Sugimoto (108) finds that if conduction is taken into account in the core, the flash leads to the appparition of a convection zone which, under certain conditions, could lead to a real explosion of the core. According to Eggleton (109), the same conduction could, for certain chemical compositions, start the flash outside the core. A considerable amount of work (no-nS) has also been devoted to the interpretation of the horizontal branch of the globular clusters, Faulkner (113) and Faulkner and lben (114) finding, in particular, that it is facilitated by adopting a much larger initial abundance of He than is customary for population II stars. The effects of mass loss on stellar evolution have continued to be studied by different authors (n9-124) and the possible effects of a variable G on the evolution of the Sun (125, 126) have been considered. A beginning has been made on the evolution of pure helium stars (127-130) and some models for pure carbon stars have also been built (131, 132). The very important problem of the evolution of close binary systems taking into account the exchange of mass between the components has received serious attention by Kippenhahn and Weigert (133), by Paczynski (I34• I35) and Zialkowski (I36, 137) and by Efrenov (I38). In view of tackling the evolution of these systems after the start of helium burning, Giannone (I39) has constructed main-sequences for models comprising a helium core and an envelope with high hydrogen content for various values of the ratio of the mass of the core to the total mass.

Last stages of stellar evolution

The idea that planetary nebulae constitute an intermediary stage in the evolution towards the white dwarf stage has received much attention from a theoretical as well as from an observational point of view and has been particularly developed by Savedoff (I40). Vila (14I) and Chin, Chiu and Stothers (142) have followed the evolution of hot stars of o·7 to 2M® with high initial luminosity after complete exhaustion of the nuclear fuel. In the HR diagram, their models do indeed evolve from the region of planetary nebulae to the white dwarf region. They also find that neutrino losses accelerate considerably the contraction and lead to better agreement with observations. Rose (143) finds that models of small mass stars with a helium envelope in which nuclear reactions take place evolve like planetary nebulae. According to Kahoutek (144) the latter could be produced by novae while Deeming (I45) considers that they could issue from infrared supergiants. Let us recall however that some opposition to these views has been expressed by Woolf (146). Mestel and Ruderman (I47) have evaluated the energy content of white-dwarfs and their rate of cooling. The possible influence of mass loss on the formation of white dwarfs has been considered by Auer and Woolf (I48) and by Williams (I49). The evolution of stars with masses in excess of the Chandrasekhar limit, during the phases preceding a supernova explosion has been studied by Chiu (ISO) and by Rakavy and Shaviv (ISI). Takarada et al. (I52) have evaluated the relation between central densities and temperatures in polytropic or isothermal configurations to estimate the general features of advanced stages of evolution. BIBLIOGRAPHY I.

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41. Schatzman, E. 1963, The early Stages of Stellar Evolution, m Star Evolution, Ed. Gratton, L., Academic Press, New York and London, p. 177. 42. Schatzman, E. 1966, Role of Magnetic Activity during Stellar Formation, in Stellar Evolution, Eds. Stein, R. F., Cameron, A. G. W., Plenum Press, New York, p. 215. 43· Penston, M. V. 1966, Observatory, 86, 121. 44• Morris, S. C., Demarque, P. 1966, Z. Astrophys., 64, 238. 1965, Nauchnye lnfor45· Massevitch, A. G., Ruben, G. V., Lomnev, S. P., Popova, E. I. matsii Astr. Sov. Acad. Nauk SSSR (Scientific Informations of the Astr. Council USSR Acad. Sci.), 1, 2. 46. Massevitch, A. G., Ruben, G. V., 1966, Nauchnye lnformatsii Astr. Sov. Acad. Nauk. SSSR, 3, 37· 47· Popova, E. I. 1967, Sbornik 'Peremennye Zvezdy i Zvezdnaya Evolutsiia' (Variable Stars and Stellar Evolution) 'Nauka', Moscow (in press). 48. Massevitch, A. G., Popova, E. I. 1967, Nauchnye lnformatsii Astr. Sov. Acad. Nauk SSSR, 6 (in press). 49· Ruben, G., Massevitch, A. G. 1966, Astr. Zu., 43 1 499· so. Ruben, G. 1966, Mitt. astr. Ges., 19. 51. Tutukov, A. V. 1966, Nauchnye lnformatsii Astr. Sov. Acad. Nauk SSSR, 4· 1965, Astrophys. J., 142, 174. 52. Weymann, R., Sears, R. L. 53· Fritze, K. 1966, Monatsber. Deutschen Acad. Wiss. Berlin, 8, 7· 1966, Acta Astr. Pol. Acad. Nauk (in press). 54· Ziolkovsky, G. 1965, Astrophys. J., 140, 1041. 55· Bahng, J, 56. Auman, J. R., Bahng, J. 1965, Astrophys. J., 142, 170. 57· Imshennick, V. S., Nadezhin, D. K. 1966, Astr. Zu., 43· 1965, Ann. Astrophys., 28, 643. 58. Gabriel, M., Ledoux, P., Denis, C. 59· Boury, A. 1964, Astrophys. J., 140, 1322. 6o. Imshennick, V. C., Kotok, E. V., Nadezhin, D. K. 1965, Nauchnye lnformatsii Astr. Sov. Aced. Nauk SSSR, 1, 48. 1966, Nauchnye lnformatsii Astr. Sov. Acad. Nauk SSSR, 3, 52. 61. Frantsman, Yu. L. 62. Bennick, A. H., Motz, L. 1965, Astrophys. J., 141, 195. 1966, Internal Structure and Vibrational Stability of wholly convective 63. Gabriel, M. Red Dwarfs, Coli. on Late-Type Stars, Trieste, p. 347· 64. Stothers, R. 1963, Astrophys. J., 138, 1074. 1964, Astrophys. J., 140, 510. 65. Stothers, R. 66. Stothers, R. 1966, Astrophys. J., 143, 91. 67. Stothers, R. 1966, Astrophys. J., 144, 954· 1967, Nauchnye Informatsii Astr. Sov. Acad. Nauk 68. Kotok, E. V., Nadezhin, D. K. SSSR, 6. 69. Kotok, E. V. 1965, Astr. Zu, 42, 1221. 70. Kotok, E. V. 1966, Nauchnye lnformatsii Astr. Sov. Acad. Nauk SSSR, 3, I. 71. Kotok, E. V. 1966, Astr. Zu., 43, 316. 72. Kotok, E. V. 1966, Astr. Zu., 43, 1025. 73· Nadezhin, D. K. 1966, Nauchnye lnformatsii Astr. Sov. Acad. Nauk SSSR, 4· 74· Vander Borght, R. 1964, Austr. J. Phys., 17, 165. 75· lben, I. Jr. 1964, Astrophys. J., 140, 1631. 76. Iben, I. Jr. 1966, Astrophys. J., 143, 483. 77• lben, I. Jr. 1966, Astrophys. J., 143, 505. 1966, Astrophys. J., 143, 516. 78. lben, I. Jr. 79· lben, I. Jr. 1967, Astrophys. J., 147, 624. So. Kippenhahn, R., Thomas, M. C., Weigert, A. 1965, Z. Astrophys., 61, 241. 1966, Z. Astrophys., (in press). 81. Kippenhahn, R., Thomas, M. C., Weigert, A. 82. Weigert, A. 1965, Mitt. astr. Ges., 19, 61. 83. Hofmeister, E. 1965, Mitt. astr. Ges., 19, 90. 84. Hofmeister, E. 1965, Proc. IAU Coll. Bamberg, p. 224. Kl. Veroff. Remeis-Sternw. Bamberg, 4, no. 40. 1966, Nauchnye lnformatsii Astr. Sov. Acad. Nauk SSSR, 3, 77· 85. Dluzhnevskaya, 0. B.

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COMMISSION 35 Varskovsky, Y. I. 1966, Nauchnye Informatsii Astr. Sov. Acad. Nauk SSSR, 4· Percy, J. R., Demarque, P. Astrophys. J. (in press). 1966, Izv. Krym. astrofiz. Obs., 36. Kopylov, I. M. 1966, Izv. Krym. astrofiz. Obs., 36. Efremov, Yu. N., Kopylov, I. M. 1966, Acta Astr. Pol. Acad. Nauk (in press). Ziolkovsky, G. Frantsman, Yu. L. 1967, Nauchnye Informatsii Astr. Sov. Acad. Nauk SSSR, 6. Auman, J, R. 1965, Astrophys. J., I42, 462. Morris, S. C., Demarque, P. 1965, Astr. J., 70, 145· Hallgren, E. L., Demarque, P., Astrophys. J. (in press). 1966, Astrophys. J. (in press). Hallgren, E. L. Paczynski, B. 1966, Postepy Astr., I4, 3· Massevitch, A. G., Ruben, G. V., Lomnev, C. P., Frantsman, Yu. L. 1966, Nauchnye Informatsii Astr. Sov. Acad. Nauk SSSR, 4· (To be published.) Reiz, A., Petersen, J. 0., Hejlesen. Demarque, P., Percy, S. R. 1964, Astrophys. J., I40, 524. 1965, Proc. First Conf. on Planetology and Space Mission Planning. Chiu, H. Y. Sears, R. L. 1964, Astrophys. J., qo, 477· 1966, Solar Models and Neutrino Fluxes, in Stellar Evolution, Eds. Stein Sears, R. L. R. F., Cameron, A. G. W., Plenum Press, New York, p. 245· 1964, Planet. Space Sci., I2, I19. Pochoda, P., Reeves, M. Bahcall, J, H., Davis, R. 1966, in Stellar Evolution, Eds. Stein, R. F., Cameron, A. G. W., Plenum Press, New York, p. 241. Harm, R., Schwarzschild, M. 1966, Astrophys. J., I4S, 496. Thomas, H. C. 1965, Mitt. astr. Ges., I9, 93· Thomas, H. C. 1966, Mitt. astr. Ges., 2I. Sugimoto, D. 1964, Progr. theor. Phys., 32, 703. Eggleton, P. P. 1966, Mon. Not. R. astr. Soc., I32, 479. Osaki, Y. 1963, Pub!. astr. Soc. Japan, IS, 498. Suda, K., Virgopia, M. 1966, Astrophys. J., I43, 75· Suda, K., Virgopia, M. 1966, Astrophys. J., I43, 87. Faulkner, J. 1966, Astrophys. J., I44, 978. Faulkner, J., Iben, I. Jr. 1966, Astrophys. J., I44, 995· Petersen, J, 0. 1966, Pub!. og mindre Medd. Kobenhavns Obs., no. 186. Jorgensen, M. E., Petersen,]. 0. 1967 (to be published). Hayashi, C., Hoshi, R., Sugimoto, D. 1965, Progr. theor. Phys., 34, 885. Sugimoto, D., Yamanoto, Y. 1966, Progr. theor. Phys., 36, 17. Stothers, R. 1966, On the Theory and Evolution of completely mixed Stars with Mass Loss, Mon. Not. R. astr. Soc., I3I, 253. Tanaka, Y. 1966, Pub!. astr. Soc. Japan, IS, 47· Tanaka, Y. 1966, Progr. theor. Phys., 36. Hartwick, F. D. A. 1966, Astrophys. J. (in press). Dluzhnevskaya, 0. B. 1965, Nauchnye Informatsii Astr. Sov. Acad. Nauk SSSR, 2, I. Dluzhnevskaya, 0. B. 1966, Astr. Zu., 43, 1226. 1966, Can. J. Phys., 44, 593· Ezer, D., Cameron, A. G. W. Roeder, R. C., Demarque, P. 1966, Astrophys. J., I44, 1016. 1965, Astrophys. J., 142, 725. Divine, M. 1965, Nuovo Cim., ser. X, 36, 1267. Giannone, P., Giannuzzi, M.A. 1966, Z. Astrophys., 64, 229. Giannone, P. Cimino, M., Giannone, P., Giannuzzi, M. A., Masani, A., Virgopia, M. 1964, Nuovo Cim., ser. X, 33, 663. Deinzer, W., Salpeter, E. E. 1965, Astrophys. J., 142, 813. Noels-Grotsch, A., Boury, A., Gabriel, M. 1967, Ann. Astrophys, 30, 13. Kippenhahn, R., Weigert, A. 1966, Mitt. astr. Ges., 2I. Paczynski, B. 1966, IAU Coli., The Evolution of Double Stars, Uccle (to be published). Paczynski, B. 1966, Acta Astr. (2 papers in press). Paczynski, B., Ziolkowski, J, 1966, Acta Astr. (in press).

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Ziolkowski, J. 1966, Acta Astr. (in press). Efremov, Yu. M. 1966, Astr. Zu. (in press). Giannone, P. 1967, Z. Astrophys (in press). Savedoff, M.P. 1966, Astrophys. J., 145, 648. 141. Vila, S. C. 1966, Astrophys. J., 146, 437· 142. Chin, C. W., Chiu, H. Y., Stothers, R. 1966, Ann. Astrophys., 39 (in press). 143· Rose, W. K. 1966, Astrophys. J., 144, 1001. 144. Kohoutek, L. 1964, Bull. astr. Inst. Czech., 15, 81. 145· Deeming, T. J. 1965, Publ. astr. Soc. Pacific, 77, 443· q6. Woolf, M. J. 1966, Astrophys. J., 145, 649. 147. Mestel, L., Ruderman, M. A. 1967, Mon. Not. R. astr. Soc. (in press). q8. Auer, L. H., Woolf, M. J. 1965, Astrophys. J., 14:z, 982. 149· Williams, J. P. 1965, Ann. Astrophys., :z8, 672. 150 Chiu, Y. U. 1966, Pre-Supernova Evolution, in Stellar Evolution, Eds. Stein, R. F., Cameron, A. G. W., Plenum Press, New York, p. 179. 151. Rakavy, G., Shaviv, G. 1966, Astrophys. J. (in press). 15:z. Takarada, K., Sato, H., Hayashi, C. 1966, Progr. theor. Phys., 36, 504. 137. 138. 139· 140.

VI. STELLAR STABILITY AND STELLAR PULSATIONS j SHOCK WAVES AND NON-STATIONARY PROCESSES IN STARS

Interesting developments have occurred in the field of stellar stability during the period under review and we shall try to situate them with respect to the classical subdivisions of the subject: dynamical stability, vibrational (or pulsational) stability and secular (or thermal) stability, reviewed for instance in (1). Note. Although probably difficult to enforce, a convention might be useful here. If the time dependence is taken to be of the form exp (i at), then: (a) dynamical stability or instability might be reserved to characterize the behavior of purely conservative systems in absolute equilibrium (adiabatic perturbations, real eigenvalue of the form ,\ =

a;).

(b) Vibrational stability or instability, to characterize the damping or amplification, under the influence of non-conservative factors, of the oscillations found under (a) when the system is dynamically stable (non-adiabatic perturbations, complex eigenvalues of the form ,\ = a + ib, a = ± (a~ + i a'), a'(+ or -) due to the contributions of the non-conservative terms. (c) Secular stability or instability to characterize the amplification or damping of slow motions (for which the inertial terms are negligible) under the influence of the non-conservative effects (non-adiabatic slow perturbations, a of the form i oc, oc : + or -); thermal stability or instability, to characterize the more complicated situation where non-conservative thermal factors (for instance in some cases neutrino losses) can have very strong effects, leading to motions on a time-scale sometimes comparable to that of dynamical motions (inertial terms not necessarily negligible). (d) In the case of conservative systems in relative equilibrium (for instance, in presence of rotation) it happens that some eigenvalues become complex, due to a failing of the dynamical stability of the corresponding absolute equilibrium, the extra-relative force (for instance, due to rotation) providing the restoring force responsible for the real part of .\. In such cases (stability of rotating fluid masses for instance), the word overstability has been used in recent years and it could perhaps be kept to characterize this kind of situations although it was coined originally, and not too happily, by Eddington to denote what is called here vibrational instability. A somewhat closer case of instability of relative equilibrium may also occur in more complex circumstances as in the Rayleigh problem for convection in presence of rotation or magnetic field and has generally been called there too, overstability.

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COMMISSION 35 Dynamical Stability and adiabatic oscillations

In the case of purely radial oscillations of 'classical' stars, the essential result (namely that dynamical instability occurs only if r < 4/3 in an appreciable part of the star), has been known for some time but work has continued on interesting applications at the very beginning of stellar evolution (z), when ionization of H, He and dissociation of H 2 reduces r below 4/3 or towards the very end (3) when nuclear equilibrium tends to be established between Fe, oc-particles and neutrons or later between He, protons, neutrons and electrons pairs lowering again r below 4/3· Equilibrium between electron pairs and radiation may also lead to low values of rand recently Rakavy and Shaviv (8) have found that this can render a large mass star dynamically unstable before nuclear equilibrium gets established. The newly discovered dynamical instability due to General Relativity corrections in large mass or very dense stars has been the object of further investigations reviewed mostly in Section II. Let us add Chandrasekhar's discussion (4) of this factor in ordinary white dwarfs and the investigations of Baglin (5) who has further taken into account the effects of finite temperature and of equilibrium between electrons and nuclei and gives critical masses and radii beyond which dynamical instability occurs for different values of the mean atomic weight. The overtone radial adiabatic oscillations of massive stars have been studied numerically by Vander Borght (6) and the results compared with the analytical asymptotic behavior. Bhatia and Kushwaha (7) have studied the radial adiabatic oscillations of a generalized Roche model. From a methodological point of view, the energy method seems to have become more popular (8, 9) following a very clear unpublished presentation by Dyson. In (8) a beginning is made in the discussion of the third order terms. Non-radial oscillations have been the object of concentrated numerical attacks by Smeyers (xo) and by Van der Borght and Wan Fook Sun (n) taking into account the full 4th order problem when the perturbation of the gravitational potential is not neglected. The application (12) of the variational principle derived by Chandrasekhar for non-radial oscillations has led directly or indirectly to some clarifications. As far as the interaction between dynamical instability towards these oscillations and Schwarzschild's criterion for convective stability is concerned we have already referred, in Section IV, to Lebovitz's proof of the existence of unstable g-modes as soon as Schwarzschild's criterion is violated in a region however small. Ledoux and Smeyers (13) have discussed the complete spectrum in such cases and shown that the g-spectrum splits then into two spectra both converging to zero, one positive (stable) corresponding to oscillations with large amplitudes and nodes in the convectively stable region and rapidly decreasing amplitudes in the convectively unstable region and one negative (unstable) with amplitudes whose behavior is exactly the opposite. The latter are actually the modes studied by Schwarzschild and Saslaw (cf. Section IV) in relation with penetrative convection. Detailed examples by Smeyers (xo, b) are in the course of publication. Furthermore, from the work of Chandrasekhar and Lebovitz, it became clear (cf. Robe, 14) that the so-called /-modes constitute really the extension to compressible configurations of the unique Kelvin spectrum for the incompressible sphere (one mode only per value of the degree l of the spherical harmonics). For l = I, this /-spectrum vanishes in compressible as well as in incompressible configurations while in compressible masses the p- and g-spectra subsist for this value of l (xo ). Robe and Brandt (15) have applied the variational method using a five parameter trial function to polytropes of indexes n = I, 2, 3, 4 and find that the method does not seem to converge for the /-mode when n > 3· This is probably due to the peculiar behavior, in highly concentrated models, of the eigen~olutions for the f- and first p-modes which acquire 'spurious' nodes as shown in detail by Robe (x6). As an illustration of the possible effects of a finite rotation on non-radial oscillations, Cretin and Tassoul (17) have studied the case of a homogeneous compressible cylinder rotating

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uniformly around its axis with angular velocity Q. They find that the azimuthal degeneracy is lifted by rotation and that, for Q smaller than some critical value, the g-modes (which in absence of rotation are unstable in this case) have complex frequencies, the real part increasing with Q. Of course the imaginary part corresponds to the energy available due to the strong convectively unstable stratification in the model. One may expect this result to remain valid for the unstable g-modes of any configuration comprising a region in which Schwarzschild criterion for convective stability is violated and Ledoux (18) has suggested that this might provide an explanation of both the maintenance and the order of magnitude of the periods of the oscillations observed in magnetic variable stars. Robe (19) is extending the work of Cretin and Tassoul and of Ostriker (2o) to general polytropic cylinder with and without rotation and tries to disentangle, in these cases, the gravitational instabilities proper from the convectively unstable gravity-modes (g-modes). Zahn (::u) is tackling again the more realistic problem of the oscillations of a rotating star especially in view of possible resonance in close binaries. A review of the principle and of some applications of the higher order virial method has been prepared by Chandrasekhar (22) and new applications have been the subject of different papers (23) (24) which, although somewhat formal, provide interesting examples of detailed analysis of complex situation in presence of uniform or differential rotation and tidal effects. Let us note also an extension of Chandrasekhar's variational principle to the 6th order problem of the oscillations of an elastic sphere by Ottelet (25) and others to the oscillations of a gaseous mass in presence of a rotation by Clement (26) or of a magnetic field by Kovetz (27).

Vibrational Stability and non-adiabatic oscillations Boury (28) has shown that the critical mass associated with the vibrational instability of helium stars is about 8 to 10 M 0 as compared to some 6o M 0 for stars on the main sequence burning hydrogen. Gabriel and Bovie-Thirion (29) have discussed the importance of the vibrational instability which manifests itself in a small mass star going through the phase of deuterium burning as a function of the initial abundance of the latter. Perdang (30) has discussed in great detail the behavior and the effects of the 3a reactions in pulsating stars. Gabriel (31) has confirmed, on the basis of fairly realistic models, the significant vibrational instability of small mass stars (M < o·27 M 0 ) on or close to the main sequence due to both the energy generation and the low values of the T's in the external ionisation zones of Hand He. Noels, Boury and Gabriel (32) have shown that quasi-static models of pure carbon stars are strongly vibrationally unstable in presence of neutrino emission however small their masses. Epstein (33) has attacked numerically the general linear problem of the non-adiabatic radial oscillations treated as a complex differential system of 4th order with complex eigenvalues. Unno (34) is reporting detailed work on the role of a convective envelope upon the vibrational stability of a star, based on a generalization of Vitense mixing-length theory of convection to the time-dependent case. In a similar line, Gough (35) finds that energy transport by convection in the external layers can have, depending on the circumstances, either a stabilizing or a destabilizing influence and he suggests that the latter may be related to the variability of the long period variables. Kopal (36) has studied some aspects of the interactions of matter with radiation in the fundamental mode of radial oscillations and finds that they can be significant only in models with very high central condensation. An attempt at evaluating the effect of gravitational contraction keeping the terms in the velocity of contraction as well as the time variations of p and p was made by Meurice (37) for a star close enough to the main sequence to be wholly radiative but the thermonuclear energy generation being still negligible. A rough evaluation of the very complicated expression of the coefficient of vibrational instability failed to reveal any significant effect. A somewhat similar

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problem has been considered by Kato and Unno (38) both for radial and non-radial oscillations around a quasi-equilibrium state in which the nuclear energy generated is not exactly balanced by the heat flux. They find that the region of decreasing entropy (as the star evolves) works in general to excite pulsations. Let us turn now to investigations directly oriented towards the problem of the excitation of the pulsations of variable stars. Alyoshin (39) concluded on the basis of an approximate model of a cepheid that the ionization zones of H and He r could not lead alone to the excitation of pulsations. Takeuti (40) has written down a boundary condition at the photospheric level of the pulsating radiative atmosphere of a cepheid. Unno (41) has discussed the linear radial pulsation of such an atmosphere to obtain boundary conditions for the pulsation of the interior of a cepheid model. He finds that, very generally, the first overtone as well as the fundamental mode are excited. The paper contains also a discussion of the propagation of running waves in a corona and remarks on the breaking down of the linear theory in the ionization zones as well as suggestions for an approximate non-linear treatment of the external zones. Simon (42) has also analyzed the effects, both from the points of view of dissipation and of phase-shifts, of progressive waves on the non-adiabatic oscillations of an atmosphere surrounded by a hot corona discussing especially the case of resonance between a proper frequency of the atmosphere and that of the exciting mechanism. In an extension of their previous work, containing many improvements, Baker and Kippenhahn (43) have discussed very fully the vibrational stability of actual models along their evolutionary tracks across the cepheid strip confirming the instability due essentially to the second helium ionization although the first helium and hydrogen ionization contribute to it especially for the first overtone. Hofmeister (44) has amplified their investigation of the problem producing a theoretical period-luminosity relation in good agreement with observations and discussing the period changes and the period-frequency relation as they follow from the theoretical evolutionary sequence. In an interesting paper, dealing with a simple one-zone model, Baker (45) has isolated the essential physics at the basis of the pulsational instability in cepheids and Unno and Kamijo (46) have generalized somewhat his discussion. Baker has also investigated the pulsational properties (47) of outer layer models of RR-Lyrae stars. The vibrational stability towards non-radial oscillations of large mass stars has been studied by Wan (48) who shows that the coefficient of vibrational stability increases with the mass for the f- and g-modes. It decreases for the p-modes when the mass increases but so slowly that it is not likely that any significant critical mass should exist. Applications to variable stars

As far as the excitation of linear oscillations is concerned, the problem has already been dealt with at the end of the subsection on vibrational stability. There have been however some other applications of the linear theory mainly concerning the periods given by the eigen-value problem corresponding to the adiabatic approximation. The essential point is to obtain a reasonable model for the internal structure of the variable considered either by direct evolutionary computations or by approximate evolutionary considerations. If the luminosity and radius can be determined more or less directly from the observations, then one can try to adjust the mass and to some extent the model, its chemical composition, etc. in such a way that the theoretical period, corresponding in most cases to the fundamental mode, be just equal to the observed period. Investigations of this type have been reported for 7J Aquiliae, RT Aurigae, X Cygni, Mira Ceti and some RR Lyrae stars by Masani et al. (49) who seem however to have used an unduly complicated approach intended, in principle, to yield also the effects of the non-adiabatic terms. Jorgensen and Petersen (so) have applied the method to derive indications on the masses of RR Lyrae stars of type a, b and c in different clusters.

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The same authors (50) have also discussed the secular changes in the periods of (3 Cephei stars on the basis of actual evolutionary sequences. The smallness of the observed changes leads them to conclude that the (3 Cephei phase must occur essentially in the slow mainsequence stage a conclusion in agreement with the values of the periods themselves. They also note that the ratio of the periods of the first overtone to that of the fundamental mode does not agree with those derived by van Hoof from the observations. Stothers (51) has also discussed this problem and using Van Hoof's data finds that (3 Cephei stars of lower mass should lie closer to the initial main sequence. For the same stars Hitotuyanagi and Takeuti (52) find that the pulsation constant should be o·o21. The interpretation of Fernie's period-radius relation for variable stars has been discussed by Demarque and Percy (53) and by Gough, Ostriker and Stobie (54). Van der Borght and Murphy (55) have studied the non-linear adiabatic oscillations of a 10 M® star up to the third order terms in (orfr) including up to the 5th overtone as spatial coefficients in the development of (orfr). They obtain appreciable skewness of the variations comparable to that observed in cepheids. Alyoshin (56) has determined the amplitudes of the auto-oscillations of the model whose vibrational instability was discussed in (39) and has discussed the growth of their asymmetry from the interior to the surface as well as the variation of the phase-lag. In another paper (57) taking into account the effects of convective transfer, he finds that, in order to get self-excited oscillations and the right-phase shift, the ratio of the mixing-length to the scale height should be smaller than some upper limit of the order of unity. The direct computational attack of the full non-linear non-adiabatic problem of stellar pulsation has been reviewed by Christy with emphazis on computational methods and RR Lyrae stars (58) and on the cepheid instability strip (59). In these review articles, as well as in the important paper on RR Lyrae models (6o), the author has attempted to clarify as far as possible the physical nature of the effects at the origin of the different characteristics of the computed self-oscillations. A comparison of his own work with the somewhat different approaches due to Zhevakin and Cox and Whitney, reveals that the criteria to which they lead for the location of the Cepheid pulsational strip in the HR diagram are of remarkably similar physical content and require essentially that the depth of He II ionization be such that the heat content of the overlying layers is about I/4 of the heat radiated in a period. Christy points out also the weaknesses of the present calculations, as for instance the lack of an adequate treatment of time-varying convection in the external instability-layers associated with the ionization of H and He and the limitations of the technique by which they are carried out which may be responsible for the difficulties in relating the finite self-excited modes found (sometimes the fundamental, sometimes the first overtone) to the linear instability which in some cases extends to many overtones. In some ways, this is somewhat reminiscent of the weakly non-linear mechanical systems whose linear modes have uncommensurable periods and in which limit cycles, if they exist, are close to one or more of these linear modes (61). Another aim of Christy's non-linear pulsation computations has always been to derive some of the unknown parameters like total mass or the abundance of He for a given variable star by adjusting these parameters so that the theoretical pulsation fits as well as possible with the observed one and recent extensions in these directions have been made to cepheids (62) and RV Tauri stars (63). Let us note also a new attempt (64) to include a more detailed treatment of radiative transfer and of the development of ionization and shock fronts in the external layers of RR Lyrae models. A review of some aspects of the non-linear problem insisting more on the growth from linear instability to finite amplitude for a stellar envelope with the position of and the luminosity at the bottom fixed can also be found in a paper by}. P. Cox (65) and a detailed investigation has now been published (66). It is remarked there that the rather small limiting

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finite amplitude suggests that the limiting mechanism is determined primarily by a saturation effect of the driving mechanisms (varying opacity and low value of 1< in the He+ ionization zone). This paper contains also a discussion of the theoretical location of the cepheid strip in the HR diagram. A note by Christy (67) offers some comments and comparisons with his own work. The thermally excited non-linear oscillator studied by Moore and Spiegel (68) is physically rather directly related to the kind of vibrational instability arising for acoustic modes (or non-radial p-modes) in a super-adiabatic region. This may however be directly relevant for some variable stars and, in any case, as noted by the authors, this oscillator provides a good illustration of the variety of behavior, including irregular variability, which can be generated by a single mechanism. In further work, with Baker (69), they have extended their non-linear analysis to a model more akin to the radial pulsation of cepheids. We may perhaps add here references to work on the interpretation of the activity of flarestars (7o, 71) and to a review of observational data and theoretical inferences concerning magnetic variable stars (72). Secular and Thermal Stability

These questions which up to recent times had received relatively little detailed attention have suddenly come to the fore with the numerical discovery of secularly unstable phases in the course of the evolution of models with non-degenerate helium burning shells. On the occasion of the first case discovered, Schwarzschild and Harm (73) developed a linear analysis of the situation of the type suggested by Ledoux (74), but including the terms due to entropy variations, which illustrates the origin and characteristics of the responsible incipient secular instability. Since then, this type of linear analysis has been repeated by Rose (75) for similar models and Gabriel (76) has found that models with an isothermal core followed by a shell burning zone become secularly unstable, when the core reaches the Schi:inberg-Chandrasekhar limit, towards a displacement corresponding to a contraction of the core and an expansion of the envelope. Quite generally, at least the linear secular instabilities in question appears for perturbations more general (often with nodes inside the star) than the homologous modification which for so long was the only one considered in the discussion of secular stability. The elucidation of some of the mathematical properties of the problem would be very welcome. Kippenhahn (77) and Weigert (78) on their side, encountered the same kind of problem in following the late evolution of a 5 M® star but found numerically that the thermal runaway gave rise to some kind of 'relaxation oscillations' of long periods (,_, 3000 years). Recently Schwarzschild and Harm (79) found that, in their case also, the secular instability discovered earlier leads indeed to long period 'relaxation oscillations' which, after about a dozen relaxation cycles (at which time the helium burning shell is still entirely non-degenerate), causes mixing of hydrogen into the hot interior. Rose (75/b) was led to similar conclusions in his study of models of helium shell-burning stars and points out that the origin of planetary nebulae and the occurrence of novae may be associated with this instability. It has subsequently been shown (So) that thermal instability can lead to vibrational instability, a circumstance that provides further physical basis for the above suggestion concerning planetary nebulae and novae. Rakavy and Shaviv (9) have also encountered significant thermal instabilities in presence of neutrino emission. It is obvious that a new and important field of research has been opened here for both the linear and non-linear theories of stellar stability and that a careful choice of descriptive terms will help avoid confusion. Shock waves, Novae, Supernovae and other sources of extreme energy release

It is quite beyond the present reviewer's ability to cover the abundant literature on shocks in all the various circumstances that have been considered. Many of these refer to conditions

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not specially typical of stellar interiors and we shall have to ignore them even if something could be learned from them for the problems of interest to this Commission. Much of the typical work has been associated with the discussion of novae or supernovae explosions and a general review of the relevant theories is due to Schatzman (81 ). As to the effects of nuclear reactions started by the collapse of the initial configuration, the problem has been reviewed by Fowler and Hoyle (82) and it has been discussed again by Masani et al. (83) who took also into account radiation, pair production, relativity effects and neutrino emission. Colgate and White (84) came to the conclusion that thermonuclear reactions had a negligible effect in circumstances likely to occur in supernovae and that the reversal of the collapsing motion in the envelope and the formation there of strong relativistic shock waves was due to the deposition of energy by neutrinos. Masani et al. (85) have extended their computations to the case of very high densities such as might occur in neutron stars. Kalenichenko and Porfiriev (86) have followed numerically the outburst of a massive hydrogen star caused by an instantaneous release of a large amount of energy at the centre and compared the luminosity curve with observational data for supernovae type II. Finzi and Wolf (87) have found two types of massive (1·4 and 1·2 M 0 ) white dwarfs models which, by implosion at the end of a slow contraction (due to inverse (3 processes), could account for type I supernovae and their frequency. Let us also note some papers (88, 89) treating some consequences of the current ideas on supernovae and refer to a general discussion of the subject (90). Schatzman (91) has considered a mechanism in which resonance could lead to ordinary novae explosions and Kahoutek (92) has also contributed to the problem of the origin of novae and planetary nebulae. Ishizuka, Hashimoto and Ono (93) have generalized the quasi-stationary method of Ono et al. to the case of oblique shock propagation and discussed in detail the behavior of a shock in polytropic gases. Simon (94) has discussed the stability of shocks by the normal-modes method. Let us also mention a few investigations (95---98) directed towards applications to the external layers of variable stars or which might be of interest in this respect. Before leaving this section, let us add a word about some other aspects of oscillations typical of the very external layers but which might be significant for the problems of internal structure either because they might remain significant at greater depth or because they might play a role in the determination of surface boundary conditions when the latter become critical for the internal structure. In the first group, I want to mention especially one result of Spiegel (99) who finds that, in a superadiabatic region, acoustic modes can be excited directly by conduction. By analogy, one might expect that non-radial p-modes in the interior could become vibrationally unstable due to the same mechanism. In the second group, which will certainly be reviewed in some other Commission, let us simply cite by title, a few papers (mo-104) devoted to the excitation of waves and oscillations in a stable atmosphere by the convection and turbulence in an underlying convection zone. BIBLIOGRAPHY

(a) Ledoux, P. 1965, Stellar Stability, in Stars and Stellar Systems, 8, Eds. L. H. Aller and D. B. McLaughlin, Univ. of Chicago Press, Chicago, Chap. X., p. 499; (b) 1964, Some general Comments on the Problem of Stellar Stability, Astrophys. Norv., 9, 187 (volume dedicated to Professor S. Rosseland on the occasion of his 7oth birthday). 2. Cf. for instance: Hayashi, C., Nakano, T. 1965, Progr. theor. Phys., 34, 754· 3· Kaminishi, K. 1965, Progr. theor. Phys., 34, 424; Colgate, S. A., White, R. H. 1966, Astrophys. J., 143, 626; Barbon, R., Dallaporta, M., Perinotto, M., Sussi, M. G., Mem. Soc. astr. ital., 36, 127, 1966. For the effects of nuclear excitation on the T's, cf.: Perdang, ]. 1966, Bull. Soc. R. Sci. Liege, 35, 369. 4· Chandrasekhar, S. 1964, Phys. Rev. Lett., 12, n4; Chandrasekhar, S., Tooper, R. F., 1964, Astrophys. J., 139, 1396. I.

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5· Baglin, A. 1964, C. r. Acad. Sci. Paris, 258, 5801; 1965, ibid., 26o, 2429; 1966, Ann. Astrophys., 29, 103. 6. Van der Borght, R. 1964, Bull. Acad. R. Belgique, Cl. Sci., seme ser., so, 959· 7• Bhatia, K., Kushwaha, R. S. 1964, Appl. Sci. Res. A. Nether!., 12, 454· 1966, The Linear Star Model and Dynamical Instability, 8. Stothers, R., Frogel, J. A. Astrophys. J. (in press). 9· Rakavy, G., Shaviv, G., 1966, Instabilities in Highly Evolved Stellar Models, Astrophys. J. (in press). 10. Smeyers, P. 1966, Thesis, Universite de Liege. This work contains detailed results for two values of f3c = o·4 and o·8 or (M/M®)il 2 = 9·85 and 77"7 and for f, p and g-modes up to the 4th order (exceptionally g 10 , g 14 , g 18) for spherical harmonics of degree l = 1 to 8. The behavior of the solutions close to the singularities at the centre and the surface are also studied in great detail. In this last respect cf. also: Lebovitz, N. R. 1965, Astrophys. J., 142, 229. Partial results are being published separately: (a) Smeyers, P. 1966, Oscillations lineaires et adiabatiques d'une sphere homogene, Bull. Acad. R. Belgique, Cl. Sci., seme Ser., 52, I 126; (b) 1966, Oscillations non radiales et convection dans les etoiles, Ann. Astrophys., 29, 539· (c) 1967, Oscillations non radiales adiabatiques d'etoiles massives, Bull. Soc. R. Sci. Liege (in preparation). I I . Van der Borght, R., Wan, F. S. 1965, Bull. Acad. R. Belgique, Cl. Sci., seme ser., 51, 978, in which the results are given for (M/M®)il 2 = 10, 20, 30, 40, so, 6o, 70, 8o; 1966, Austr. J. Phys., 19, 467 which contains an analysis of Cowling's perturbation method for correcting the results of the second order problem of the effects of the perturbation of the gravitational potential. 12 Chandrasekhar, S., Lebovitz, N. R. 1964, Astrophys. J., 140, 1517. IJ. Ledoux, P., Smeyers, P. 1966, C. r. Acad. Sci. Paris, 262, 841. 1965, Bull. Acad. R. Belgique, Cl. Sci., 5eme ser., 51, 598. 14. Robe, H. 1966, Ann. Astrophys., 29, 571. 15. Robe, H., Brandt, L. 1966 (in preparation). 16. Robe, H. 1965, Ann. Astrophys., 28, 982. 17. Cretin, M., Tassoul, J. L. 18. Ledoux, P. 1965, Oscillation theories of Magnetic Variable Stars, in Proc. Symp. on Magnetic Stars and other Peculiar and Metallic-Line Stars, Goddard Space Flight Center, Greenbelt, Maryland (to be published). 1966 (in preparation). 19. Robe, H. 20. Ostriker, J. 1964, Astrophys. J., 140, 1529. 21. Zahn, J.P. 1966, C. r. Acad. Sci. Paris, 263, 1077. 1964, The Higher Order Virial Equations and their Applications 22. Chandrasekhar, S. to the Equilibrium and Stability of rotating Configurations, in Lectures in Theoretical Physics, vol. 6. The University of Colorado Press, Boulder. 23 Chandrasekhar, S. 1964, The Equilibrium and the Stability of the Darwin Ellipsoids, Astrophys.J., 140,599; 1965, The Equilibrium and the Stability of the Dedekind Ellipsoids, ibid., 141, 1043; 1965, The Equilibrium and the Stability of the Riemann Ellipsoids, 1., ibid., 142, 89o; 1966, II, ibid., 145, 842. 24. Lebovitz, N. R. 1966, On Riemann's Criterion for Liquid Ellipsoids, Astrophys. J., 145. 872. 25. Ottelet, I. 1966, Astrophys. J., 143, 253· 26. Clement, M. ]. 1965, Astrophys. J., 141, 210. 1966; Astrophys. J., 146, 462. 27. Kovetz, K. 28. Boury, A. 1965, Ann. Astrophys., 28, 353· 29. Gabriel, M., Bovie-Thirion, C. 1965, Bull. Acad. R. Belgique, Cl. Sci., seme ser., 51, 1330. 30. Perdang, J. 1965, Bull. Soc. R. Sci. Liege, 34, 736. 31. Gabriel, M. 1966, Thesis, Universite de Liege; cf. also: 1966, Stellar Models for wholly convective red Dwarfs and their vibrational Stability, Colloquium on Late-Type Stars, Trieste, 13-17 June 1966 (in press).

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Noels-Grotsch, A., Boury, A., Gabriel, M. 1967, Ann. Astrophys. (in press). Epstein, I. 1967 (in preparation). Unno, W. 1967 (in preparation). Gough, D. 0. 1967 (in preparation). Kopal, Z. 1965, Z. Astrophys., 61, 156. 1964, Memoire de Licence, Universite de Liege. Meurice, P. Kato, S., Unno, W. 1966 (preprint). Alyoshin, V. I. 1964, Astr. Zu., 41, 1056. 1964, Pub!. astr. Soc. Japan, 16, 64. Takeuti, M. Unno, W. 1965, Pub!. astr. Soc. Japan, 17, 205. Simon, R. 1964, Astrophys. Norv., 9, I 13 (volume dedicated to Professor S. Rosseland on his 7oth birthday). 1965, Astrophys. J., 142, 868. Baker, N., Kippenhahn, R. Hofmeister, E. 1965, Thesis (Miinchen); 1965, Mitt. astr. Ges. no. 19, 90; 1965, Proc. IAU Coll. Bamberg, p. 224. Kl. Veroff. Remeis-Sternw. Bamberg, 4, no. 40. Baker, N. 1966, Simplified Models for Cepheid Instability, in Stellar Evolution, Eds. R. F. Stein and A. G. W. Cameron, Plenum Press, New York, p. 373. Unno, W., Kamijo, F. 1966; Pub!. astr. Soc. Japan, 18, 23. Baker, N. 1965, Proc. IAU Coll. Bamberg, p. 121. Kl. Veroff. Remeis-Sternw. Bamberg, 4, no. 40. Wan Fook Sun 1966, Non-radial oscillations and vibrational stability of massive stars initially composed of pure hydrogen, Thesis Australian National Univ., Canberra; Bull. Acad. R. Belgique, Cl. Sci., 5eme ser. (in press). 1965, IAU Coll. on The Position of Masani, A., Martini, A., Nelli, M., Albino, E. Variable Stars in the H-R diagram, Bamberg 1965, Kl. Veroff. Remeis-Sternwarte Bamberg, 4, no. 40; 1966, lnf. Bull. var. Stars, Com. 27 IAU, no. 162. 1966 (University Observatory, Copenhagen, in preparation). Jorgensen and Petersen 1965, Astrophys. J., 141, 671. Stothers, R. 1963, Sci. Rep. T8hoku Univ., Ser. 1., 47, 159. Hitotuyanagi, Z., Takeuti, M. 1965, Astrophys. J., 142, 1082. Demarque, P., Percy, J. R. 1965, Astrophys. J., 142, 1649. Gough, D. 0., Ostriker, J. P., Stobie, R. S. Vander Borght, R., Murphy, J. 0. 1966, Mon. Not. R. astr. Soc., 131, 225. 1964, Astr. Zu., 41, 201. Alyoshin, V. I. 1966, Astr. Zu. (in press). Alyoshin, V. I. Christy, R. F. 1964, Rev. mod. Phys., 36, 555; also, Computational Methods in Stellar Pulsation, in the series Method of Computational Physics, eds. Alder, B., Fernback, S., Rotenberg, M., Academic Press, New York and London (to be published). 1966, A. Rev. Astr. Astrophys., 4, 353; cf. also, 1966, Stellar Evolution, Christy, R. F. Eds. R. F. Stein and A. G. W. Cameron, Plenum Press, New York, p. 359; 1966, The Cepheid Instability Strip, Comm. 122nd Meeting AAS, Cornell Univ., July 25-28, 1966. Christy, R. F. 1966, Astrophys. J., 144, 108. Cf. for instance: Hale, J. K. 1963, Oscillations in nonlinear Systems, McGraw-Hill series in Advanced Mathematics with Applications, McGraw-Hill, New York, Chap. 10, p. 89; Cesari, I. 1963, Asymptotic Behavior and Stability Problems in ordinary differential Equations, Springer-Verlag, ch. 3, §8·5. Christy, R. F. 1966, Astrophys. J., 145, 337· 1966, Astrophys. J., 145, 340. Christy, R. F. Castor, J. I. 1966, Atmospheric Dynamics in a Model RR Lyrae Star, Thesis (Caltech). 1966, Stellar Evolution, Eds, R. F. Stein and A. G. W. Cameron, Plenum Cox, J. P. Press, New York, p. 347· 1966, Astrophys. J., Cox, J. P., Cox, A. N., Olsen, K. H., King, D. S., Eilers, D. D. 144, 1038; King, D. S., Cox, J. P., Eilers, D. D. 1966, Astrophys. J., 144, 1069; also King, D. S. 1966, Astr. J., 71, 3901. Christy, R. F. 1966, Astrophys. J., 144, 1212. Moore, D. W., Spiegel, E. A. 1966, Astrophys. J., 143, 871.

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69. Baker, N. H., Moore, D. W., Spiegel, E. A. 1966, Nonlinear Oscillations in the OneZone Model for Stellar Pulsation, comm. 122nd Meeting AAS, Cornell University, 25-28 July 1966. 70. Vardya, M. S. 1966, On M Dwarf Flare Stars, Mon. Not. R. astr. Soc., I3I, 521. 7I. Poveda, A. 1964, A theoretical Domain for Flare Stars in the H-R diagram, Nature, 202,4314. 72. Ledoux, P., Renson, P. 1966, A. Rev. Astr. Astrophys., 4, 293· 73· Schwarzschild, M., Harm, R. 1965, Astrophys. J., I42, 855. 74· Cf. ref. (I), § 6 and also, 1960, Bull. Acad. R. Belgique, CI. Sci., 5eme ser., 46, 429. 75· Rose, W. K. 1966a, Astrophys.J., I440 1001; 1966b, Astrophys.J., I46, 838. 76. Gabriel, M. 1967 (in preparation). 77· Kippenhahn, R. 1965, Mitt. astr. Ges., 1965, p. 53· 78. Weigert, A. 1965, Mitt. astr. Ges., 1965, p. 6x. 79· Schwarzschild, M., Harm, R. 1966 (in preparation). So. Rose, W. K. 1966 (in preparation). 8I. Schatzman, E. 1965, Theory of Novae and Supernovae, in Stars and Stellar Systems, 8, Eds. L. H. Aller and D. B. McLaughlin, The Univ. Chicago Press, Chicago, Chap. 6, p. 327; also, 1963, White Dwarfs and Type I Supernovae, in Star Evolution, Ed. L. Gratton, Acadexnic Press, p. 389. 82. Fowler, W. A., Hoyle, F. 1964, Astrophys. J. Suppl., 9, 252; Fowler, W. A. 1964, Rev. mod. Phys., 36, 545· 83. Masani, A., Borla, V., Ferrari, A., Martini, A. 1966, Shock Waves at high Temperatures, Grup. Ital. Fis. Cosm., Rapp. Interno, no. 26. 84. Colgate, S. A., White, R. H. 1966, Astrophys. J., I43o 626. 85. Masani, A., Borla, V., Ferrari, A., Martini, A. 1966, Shock Waves at high Densities, Grup. Ital. Fis. Cosm., Rapp. Interno, no. 29. 86. Kalenichenko, V. V., Porfiriev, V. V. 1966, Astr. Zu., 43, 740. 87. Finzi, A., Wolf, R. A. 1966, Orange preprint, Caltech. 88. Colgate, S. A., Cameron, A. G. W. 1963, Enhancement of Light Output from a Supernova, Nature, zoo, 870. 89. Stothers, R. 1963, Neutrino Einission, Mass Loss and the Frequency of Supernovae, Astrophys. J., I38, 1085. 90· Colloque International sur les novae, novoides et supernovae, St Michel de Haute-Provence, 3-7 September 1963, in Coli. Intern. CNRS, Presses Univ., Paris. 9I. Schatzman, E. 1964, Ann. Astrophys., 27, 590. 92. Kahoutek, L. 1964, Bull. astr. Inst. Csl., IS, 81. 93· Ishizuka, T., Hashimoto, Y., Ono, Y. 1964, Progr. theor. Phys., 32, 207. 94· Simon, R. 1964, J. Mec., 9, IIJ. 95· Bird, G. A. 1963, The Behavior of Shock Waves in a gravitational Atmosphere, Astrophys. J., I39o 675. ¢. Bhatnagar, M. S., Kushwaha, R. S. 1964, Remarks on the theory of decaying shocks in the atmosphere of fJ Cephei Stars, Proc. nat. Acad. Sci. India, Sect. A, 34, 181. 97· Skalafuris, 1965, The Structure of a Shock Front in atoxnic Hydrogen, II, The Region of Internal Relaxation, Astrophys. J., I42, 351. 98. Caloi, V., Conforto, G. 1966, Teoria non lineare delle oscillazioni nell'atmosfera di una variabile, Mem. Soc. astr. ital., 37, no. 3 {also Contr. Lab. astrofis. Frascati Roma). 99· Spiegel, E. A. 1964, Astrophys.J., I39o 959; cf. also ref. (68) above. IOO. Moore, D. W., Spiegel, E. A. 1964, The Generation and Propagation of Waves in a compressible Atmosphere, Astrophys. J., I39o 48. IOI. Kato, S. 1966, On the atmospheric oscillations excited by turbulence, Astrophys.J., I43, 372. I02. Souffrin, P. 1966, Hydrodynaxnique d'une atmosphere perturbee par une zone convective turbulente sous-jacente, Ann. Astrophys., 29, 55· I03. Townsend, A. A. 1966, Internal Waves produced by a convective Layer, J. Fluid Mech., 24, 307. I04• Bird, G. A. 1965, The Equilibrium State of a Shock heated Atmosphere, Astrophys. J., I4Io 1455·

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VII. EFFECTS OF ROTATION, MAGNETIC FIELDS, AND EXTERNAL GRAVITATIONAL FIELDS

The effects of rotation on various types of stellar models have been studied extensively but although the information gathered is valuable, the impression persists that one is still some way from a completely satisfactory physical solution. Roxburgh (I) has built models in which the angular velocity field adjusts itself so as to drive no meridional circulation. Although there is a typical difference in the resulting angular velocity distribution for upper and lower main sequence stars it is not sufficient to explain the observed difference between the two classes of stars. Polytropes in fast uniform rotation have been discussed by Duheert (2) ,James (3), Roberts, Hurley and Limber (4) and Stoeckly (S) has constructed, by direct numerical methods, polytropic models in fast, non-uniform rotation. Monaghan and Roxburgh (6) have developed an approximation method based on the use of a first order perturbation technique in the interior and the neglect of the self-gravitation in the outer envelope (Roche model). This method has been extended by Roxburgh, Griffith and Sweet (7) to the construction of more realistic models in fast uniform rotation. Models for early main-sequence stars in non rigid rotation with an increase in angular velocity towards the surface have also been obtained by Kapylov (8) while Porfirjev (9) has investigated a Roche model with barotropic rotation. Rotational oscillations connected with meridian circulations have been discussed (10) in view of the interpretation of the f3 CMa stars. Radial velocity curves for eclipsing variables have been computed taking into account an equatorial deceleration (n, 12). A relativistic generalization of the Roche model for applications to neutron stars has also been developed (9). The question of meridian circulations or the Von Zeipel-Eddington problem has been surveyed by Mestel {I3) with special reference to the problem of self-consistent circulation patterns, the effect on stellar evolution and possible observable surface effects. Steenbeck and Krause (14) have studied the differential rotation with equatorial acceleration associated, in a perfect fluid sphere, with a weak meridian circulation flowing on the surface towards the equator and descending there. Mestel {IS) has confirmed Opik's result that, in a uniformly rotating radiative envelope, the meridian circulation pattern breaks up into two zones, the velocity becoming large for low surface densities. Smith {I6) suggests that the velocity singularity arising at the surface when the density tends to zero can be removed by taking into account the non local nature of radiative transfer in the external layers. The problem of the effect of rotation in the external layers has also been rediscussed by Osaki (I7) using the appropriate equations of radiative transfer. He finds that two steady states are possible depending on whether the viscosity is negligible (redistribution of angular velocity so that the divergence of the radiative flux and the meridional circulation vanish) or not (the non-vanishing divergence of the radiation flux drives meridional circulations which maintain differential rotation). Anand (I8) has also studied polytropic models in uniform rotation but including applications to rotating white dwarfs in which case he finds that, for maximum rotation compatible with stable equilibrium, Chandrasekhar's limiting mass M 3 is increased by 3·5% in agreement with an earlier result of Roxburgh (I9) who, furthermore, discussed the possibility for a star of any mass to attain the white dwarf stage through mass loss by rotational instability. This interesting result was already apparent in James' investigation (3) although the critical mass itself was not derived by this author. The discussion of the structure of fast rotating white dwarfs has been refined by Monaghan (20). Differential rotation in white dwarfs has been taken into account by Ostriker, Bodenheimer and Lynden-Bell (2I) who find that, in this case, equilibrium models exist with masses considerably greater than M 3 • This important result suggests that, for a star above M 3 , there is an alternative to mass loss or rapid collapse in the

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final stages of stellar evolution associated with the redistribution of angular momentum. Papers on the self-consistent field method used numerically (22) and on a number of physically realistic white-dwarf models (23) are in preparation. A number of investigations were devoted to the evaluation of the effects of rotation on the observable surface characteristic (L- Teti> Mb 01 -B- V) and on the position of the model in the HR diagram (24-26). In the case of an age determination of the Pleiades on the basis of isochrones derived from the evglutionary paths of non-rotating models, it was found necessary to make appropriate corrections for effects of rotation (27). We may perhaps add a few references to semi-empirical papers presenting or discussing collections of data of direct interest for the theory. A discussion, on a large statistical basis, of interrelations between the distribution of rotational velocities on one side and evolutionary paths, early-type stars variability and 'peculiarities' on the other is due to Paczynski (28). A study of the distribution of rotational velocities with mass by Kopylov (29) shows a maximum for stars of 5-9 M®, but, on the main sequence, even this maximum is smaller than the critical velocity leading to rotational instability. In the same paper a comparison between observed velocities and predicted ones along early evolution assuming conservation of angular momentum reveals good agreement except for stars B9-A3 (region of the magnetic and peculiar Astars) for which the observed velocities along the evolutionary paths become rapidly smaller than the predicted ones. Sletteback (30) situates the minimum difference between calculated minimum equatorial breakup velocities and observed velocities at the Be stars. The problem of the interaction between stellar rotation and magnetic fields is more or less unescapable and the generation of a toroidal magnetic field in an initially non-magnetic rotating star by the battery effect of the electron partial pressure has been discussed in detail by Roxburgh (31) and the discussion has been extended by Roxburgh and Strittmatter (32) to the structure of the rotation and magnetic field inside non-uniformly rotating early main sequence stars where the limit on the growth of the thermally generated toroidal magnetic field comes from the Hall effect rather than the ohmic field. Carr (33) finds that balancing, on the average, the extra-force introduced by general relativity in a non-uniformly rotating star by a magnetic force, yields a reasonable value of the magnetic field. Equilbrium models of polytropes with magnetic fields of various geometries have been discussed by Monaghan (34) and Roxburgh (35). In his lectures on the theories of stellar magnetism (36), Mestel has reviewed the general problem of the origin of stellar magnetic field and has discussed especially various questions: role of 'weak' and 'strong' primeval fields during the Hayashi convective contraction phase including magnetic braking; the appearance or non-appearance of a field above the stellar surface; the reduction in the Cowling decay-time of a strong field; the oblique rotator and the magnetic binary-star models of magnetic variables. Cowling (37) has written a very clear account of the fundamentals of the subject and a general review is also given in the article by Ledoux and Renson (38). The study of the interaction between magnetic field and convection has also been pursued. Parker (39) and Weiss (40) have shown how in a zone which is the seat of laminar convection, a 'weak' field is steadily pushed towards the edge or concentrated in localized flux ropes within the zone. Gough and Tayler (41) find that simple local criteria (applicable in absence of intrinsic hydromagnetic instabilities) suggest a high degree of suppression of convection in a sunspot model. This work is being extended by Gough to polytropic atmospheres. This last problem has also been considered by Gusseinov (42) who shows, on the basis of convection criteria for the increase of vortexes of different scales, that small ones are depressed by the magnetic field in high atmospheric layers while, in some cases, the magnetic field adds to the convective instability. The influence of radiation has also been considered (43). Riidler (44) finds that only completely disordered turbulence intensifies the decay of the mean field. In other cases,

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especially when one of the two types of helical motion is preferred, for instance as a consequence of the Coriolis forces in a rotating body (planet or star), dynamo effects can arise (45, 46, 47) yielding different types of solutions, some periodic, depending on the distribution of rotation inside the configuration. As far as the theory of magnetic variable stars is concerned, one may record a suggestion by Steinitz (48) appealing to the over-stability due to rotation. Although the case discussed by Steinitz is rather far removed from any likely physical model, fundamentally the same overstability could act in more realistic circumstances and the advantages of an oscillation theory based on this mechanism have been discussed by Ledoux (49). In such a theory, the selection of appropriate modes of oscillation would be greatly helped by the presence of a companion as in the excentric double-star hypothesis suggested and developed by Renson (50). This last theory presents intrinsically many advantages and the possibility to explain, on its own, fieldreversals if the angular momentum and magnetic axes make a large angle although, in this case, some of the ordinary physical objections to the oblique rotator would probably persist. A discussion of the comparative merits of variable stars theories can be found at the end of the review article by Ledoux and Renson (38). We have already covered some of the work on double-stars and their evolution in Section V. Roxburgh, (51) in investigating the pre-main-sequence evolution of a rotating non-magnetic star finds that rotational instability is likely to occur for M > o·8 M 0 when a radiative core develops and that this could lead to the formation of close binaries for M < 4 M 0 and wide pairs for M > 4 M 0 • Apsidal motion in close binary system is discussed by Peraiah (52) who shows that if the components rotate faster than they revolve, the derived central densities could be higher than usually found. Zahn (53) has discussed the principal properties of tides in close binaries in absence of synchronism between rotation and orbital motion and explains three well-known effects on this basis: circularity of the orbits of binaries when at least one of the components possess an external convection zone, the presence of a superficial turbulence zone on star built on the Cowling model, the peculiar evolution of some systems when the secondary is a sub-giant. Kopal (54) has surveyed the general problem in a review paper. BIBLIOGRAPHY

1. 2. 3· 4·

5· 6. 7· 8. 9· 10.

II.

12. 13. 14. 15. 16. 17. 18. 19.

Roxburgh, I. W. 1964, Mon. Not. R. astr. Soc., 128, 157 and 237. Duhurt, M. 1964, These de 3eme cycle, Paris. James, R. A. 1964, Astrophys. J., 140, 552. Hurley, M., Roberts, P. H. 1964, Astrophys. J., 140, 583; 1966, Astrophys J. Suppl., II, 95; Limber, D. N., Roberts, P. H. 1965, Astrophys j., 141, 1439. Stoeckly, R. 1965, Astrophys. J., 142, 208. Monaghan, }. J., Roxburgh, I. W. 1965, Mon. Not. R. astr. Soc., 131, 13. Roxburgh, I. W., Griffith, J. S., Sweet, P. A. 1965, Z. Astrophys., 61, 203. Kopylov, I. M. 1967, Astr. Zu (in press). Porfirjev, V. V. 1966, Sbornik 'Voprony Astrophysiki' (Problems of Astrophysics), Publ. Naukova Dumka, Kiev. Porfirjev, V. V. 1966, Sbornik, Physics of Stars and of Interstellar Medium, Publ. Naukova Dumka, Kiev; 1963, Astr. Zu., 40, 579· Oliinik, T. T., Porfirjev, V. V. 1963, Astr. Zu., 40, 774· Kalenichenko, V. V., Porfirjev, V. V. 1965, Astr. Zu., 42, 56o. Mestel, L. 1966, Meridian Circulation in Stars, in Stars and Stellar Systems, 8, Eds. L. H. Aller and D. B. McLaughlin, Univ. Chicago Press, Chicago, Chap. 5, p. 465. Steenbeck, M., Krause, F. 1965, Mber. dtsch. Akad. Wiss. Berlin, 1· Mestel, L. 1966, Z. Astrophys., 63, 196. Smith, R. C. 1966, Z. Astrophys., 63, 161. Osaki, Y. 1966, Pub!. astr. Soc. Japan, 18, 7· Anand, S. P. S. 1966, Astrophys. J. (in press). Roxburgh, I. W. 1965, Z. Astrophys., 62, 134.

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I966, Mon. Not. R. astr. Soc., 132, 305. Monoghan, J. J. I966, Phys. Rev. Lett., 17, 8I6. Ostriker, J. P., Bodenheimer, P., Lynden-Bell, D. Ostriker, J. P., Mark, Bodenheimer, P. I967 (in preparation). I967 (in preparation). Ostriker, J. P., Bodenheimer, P. Roxburgh, I. W., Strittmatter, P. A. I965, Rotational Spread of the mam sequence, Z. Astrophys., 63, IS. I966, On Stellar Rotation, V. The Structure of 25. Roxburgh, I. W., Strittmatter, P. A. rotating Stars, Mon. Not. R. astr. Soc., 133, 345· 26. Rubin, R. I966, Effects of stellar Rotation on apparent bolometric Luminosity, Mon. Not. R. astr. Soc., 133, 339· I966, Mitt. astr. Ges., no. 21. 27. Hazlehurst, J., Thomas, H. C. 28. Paczynski, B. I966, Act. Astr. Polsha Acad. Nauk, 16. 29. Kopylov, I. M. I967, Sbornik 'Variable Stars and Stellar Evolution', Nauka, Moscow. 30. Sletteback, A. I966, Astrophys. J., 145, I26. I966, Mon. Not. R. astr. Soc., 132, 20. 31. Roxburgh, I. W. 32. Roxburgh, I. W., Strittmatter, P. A. I966, Mon. Not. R. astr. Soc., 133, 1. 33· Car, W. J. I965, Phys. Rev. 140, B237. I965, Mon. Not. R. astr. Soc., 131, IOS; I966, ibid., 132, I; ibid., 134, 34· Monoghan, J. J. 275· I966, Mon. Not. R. astr. Soc., 132, 347· 35· Roxburgh, I. W. 36. Mestel, L. Theories of Stellar Magnetism, Lectures at Enrico Fermi School on Plasma Astrophysics, Varenna I966 (to be published). 37· Cowling, T. G. I965, Magnetic Stars, in Stars and Stellar Systems, Eds. L. H. Aller and D. B. McLaughlin, Univ. Chicago Press, Chicago, chap. 8, 425. 38. Ledoux, P., Renson, P. I966, Magnetic Stars, A. Rev. Astr. Astrophys., 4, 293. 39· Parker, E. N. Stellar and Solar Magnetic Fields, IAU Symp. no. 22, Ed. Lust, R., North Holland Publ. Co., p. 232. 40. Weiss, N. 0. I964, Phil. Trans., A256, 99; Mon. Not. R. astr. Soc., 128, 225; I966, Proc. R. Soc. London, 293, 3IO. I966, Mon. Not. R. astr. Soc., 133, 85. 41. Gough, D. 0., Tayler, R. J. 42. Gusseinov, 0. Kh. I966, Astr. Zu., 43, 772. I966, Astr. Zu., 43, 3I3. 43· Zeldovitch, Ya. B., Gusseinov, 0. Kh. I966, Dissertation, Univ. Jena. 44· Radler, K. H. 1966, Z. Naturj., 21a, 369. 45· Steenbeck, M., Krause, F., Radler K. H. 1966, Z. Naturj., 21a, 1285. 46. Steenbeck, M., Krause, F. 1965, Mber. dtsch. Akad. Wiss. Berlin, 7, 335· 47· Steenbeck, M., Krause, F. 48. Steinitz, R. 1964, Studies on Magnetic Stars. Thesis, Univ. Leiden; 1965, Stellar and Solar Magnetic Fields, IAU Symp. no. 22, Ed. R. Lust, North Holland Publ. Co., p. 117. 49· Ledoux, P. 1965, Oscillation Theories of Magnetic Variable Stars, in Proc. Symp. on Magnetic Stars and the Peculiar and Metallic-Line Stars, Goddard Space Flight Center, Greenbelt, Maryland (to be published). so. Renson, P. 1963, Bull. Soc. R. Sci. Liege, 32, 664. 51. Roxburgh, I. W. I966, Astrophys. J., 143, 111. 52. Peraiah, A. I966, Z. Astrophys., 64, 27. I966, Ann. Astrophys., 29, 313, 489 and 565. 53· Zahn, J. P. 54· Kopal, Z. 1965, Internal Structure of the Stars and apsidal Motions, m Adv. Astr. Astrophys. 3, Ed. Z. Kopal, Acad. Press, New York and London, p. 89.

20. 21. 22. 23. 24.

VIII. GRAVITATIONAL INSTABILITY- ORIGIN OF STARS

The activity in this field has continued to increase probably because of various favorable factors: better and more detailed observational data on the interstellar matter and better knowledge of the physical processes taking place in it as well as the possibility of new significant observations and tests in the near future, the discovery of very cold infrared objects, new information on the structure of galaxies, a better grasp of factors arising in magnetohydrodynamics and their possible interactions with rotation and finally the access to powerful

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computers and the resulting enticement to tackle more realistic problems including non-linear ones. As a result, new factors like thermal instabilities have entered the field and others like magnetic fields and rotation have been the object of new and more precise discussions. One may also note a shift of the attention and interest towards the larger scale problem of the formation of the characteristic structures of galaxies. In this sense, many investigations are strictly outside the competence of this Commission and we shall only survey roughly part of this work when the methods used may be of some interest for the problem of the formation of stars themselves. The general problem of gravitational instability and of star formation has been reviewed by Spitzer (1), Layzer (z) and Mestel (3). Each author emphazises different aspects but all voice a certain uneasiness with the pioneering treatment of Jeans. The difficulties arise in defining properly the initial state of the system whose stability should be studied. As a finite configuration which has relaxed completely on its own and in all directions to equilibrium (mechanical and thermal) cannot exhibit gravitational instability at least for infinitesimal perturbations, a certain measure of lack of equilibrium (motions, thermal inequalities, extra gravitational field due, for instance, to pre-existing stars, etc.) should be present and this certainly increases the difficulties. Spitzer insists perhaps more on the physics of the problem. Layzer' s article contains, apart from a general critical review, a clear account of his own views which place 'gravitational clustering' at the origin of all cosmical condensations. It is further assumed that interactions among pre-stars in a pre-cluster can inhibit their gravitational contraction for periods comparable to the age of a galaxy so that systems of all levels of the hierarchy are actually born almost simultaneously. In Mestel's article, the emphasis is laid rather on anisotropic factors like centrifugal force and magnetic field, especially the latter, and a number of interesting problems are raised in this connection. Another general review by Woltjer (4) is directed more at the problem of the formation of large scale structures in a galaxy and especially spiral arms. In an attempt to elucidate some aspects of Jeans's criterion, Simon has followed the development in time of a local perturbation in Jeans medium (5) showing that, whatever the initial scale, it always leads to instability after a time which is the longer the smaller the initial dimensions. In the case of the isothermal stratified nebulae, he has established the existence of a critical wavelength of maximum instability. Lynden-Bell (7) and Lin, Mestel and Shu (8) have followed the collapse of a uniform nonrotating pressure-free spheroid showing that any initial excentricity is rapidly amplified an oblate spheroid becoming a disk and a probate spheroid a spindle. C. Hunter (9) has studied the formation, inside a large spherical cloud contracting as a whole, of gravitational subcondensations and finds that rotation has a negligible influence on the process. The effects of cooling on the contraction of interstellar cloud with an initial polytropic density distribution have been discussed by McNally (10) and Gould (n) finds that a molecular hydrogen protostar (M > I M®) would collapse due to the 28fL radiation. The general problem of the thermal stability of a dilute gas in mechanical and thermal equilibrium has been studied exhaustively by Field (12) who finds that, under a wide range of conditions, thermal instabilities exist capable of giving rise, although in times rather long, to astronomically significant condensations of higher density and lower temperature than the surroundings. In a following paper with Saslaw (13), using Oort's model, they find, for the rate of star formation ( oc p 2 ) and for the cloudmass spectrum, results in reasonable agreement with observations. The problem of the interaction of this thermal instability with gravitational instability and possibly magnetic fields has been elaborated further by J. H. Hunter (14) who shows that thermal instability at pressure equilibrium followed by gravitational collapse can lead to the formation of significant condensations of the order of 100M® in 109 to 1010 years. Thermal effects have also

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been taken into account by Simoda, Kikuchi and Unno (15) in studying the homologous contraction of an interstellar cloud represented initially by a negative polytrope (n = - 3·32) which ultimately reaches a stage of free-fall collapse except if the density is too high ( > 100 cm- 3) in which case oscillations occur. In a paper in preparation however, Kikuchi (16) finds that homologous contraction is not a good approximation and studies the effects of nonhomology. The effects of rotation, in a more or less classical approach, have been discussed in a series of papers (17-20). Some of the results here, as in the investigations of Toomre (21), of Lin and Shu (22) and of Goldreich and Lynden-Bell (23), might be more significant for the formation of large scale structures rather than stars. Mestel finds that only in special cases, does the spin of sub-condensation in a non-uniformly rotating medium have the same sign as the hydrodynamic vorticity. The general influence of magnetic fields is taken into account in (24) and (25). Some of the conclusions of the linear analysis are discussed by Strittmatter (26) who shows that, even if the linear criteria is not modified by the presence of a magnetic field, contraction in this case will not go on indefinitely. In another paper (27), the same author discusses the gravitational contraction of a cloud in presence of a frozen-in magnetic field taking into account the possibility of anisotropic flow along the field lines. He finds that a change by a factor 4 in the magnetic flux will make all the difference between complete gravitational collapse and the establishment of an equilibrium state at almost the initial lateral dimensions. Considering an anisotropic plasma, Gliddon (28) has shown that, in that case, hose instability as well as gravitational instability may occur, the criterion for the latter depending now on the magnetic field. The magnetic field of a contracting gas cloud has been studied by Mestel (29) who finds that, if the flux-freezing constraint is strictly enforced, the non-homologous contraction of a gas to form a cloud yields a distorted field that exerts strong pinching forces just beyond the cloud radius. Relaxation of the flux-freezing allow the field lines to snap, yielding a magnetically isolated cloud. A simple illustration model for this snapping has been worked out (30) while, in another investigation (31). the relative importance in this context of the Sweet mechanism, ambipolar diffusion and the Petschek mechanism are being discussed. Of course once magnetic detachment has occurred, transport of angular momentum from the cloud ceases and the possibility of magnetic braking vanishes. However the latter will persist as long as the cloud field is undetached and its effects are being studied in two cases: gravitational collapse (32) and slow contraction due to a sufficiently strong centrifugal force (33). Mestel (34) has also considered the effect of magnetic braking on the evolution of a protostar in the Hayashi phase assuming a strong stellar wind. He shows that, in the case of a double star system with a strong coupling between orbital and spin motions, this effect could lead to the formation of a close binary. The question of magnetic coupling between the stars is also considered. The question of the ultimate fate of fragments formed by sub-condensation in a contracting cloud has· been the object of some controversy, the linear contraction time-scales being of the same order for the fragments and the cloud as a whole. Layzer (35) has advocated other factors favoring the coalescence of the fragments by collisions. Hunter (36) has shown that the effects of non-linear terms invalidate some of Layzer's arguments and Nakano (37) assuming that the initial large cloud is endowed with some angular momentum finds that, despite some coalescence and disintegration of fragments, the theory can lead to mass-functions which are not incompatible with observations in galactic clusters. Amy (38) has introduced an interesting approach covering the essential non-linear and thermal effects for studying fragmentation and the growth of sub-condensations in large clouds

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which may themselves be in internal motion and especially in contraction. He has also considered the same problem as that tackled by Nakano and arrives at more detailed and somewhat different conclusions (39). Finally, let us mention that the possibility of star formation from superdense matter has been considered by Imshennik, Nadezhin, Pinaev and others (40).

BIBLIOGRAPHY I.

2. 3· 4· 5· 6. 7• 8. 9· xo. II. 12.

13· 14· 15. 16. 17. x8. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. JI. 32. 33·

Spitzer, L. I967, Dynamics of Interstellar Matter and the Formation of Stars, in Stars and Stellar Systems, 7 (to be published); I965, Physical Processes in Stars Formation, in The Structure and Evolution of Galaxies, Proc. I 3th Conf. Phys. Brussels, I964, lnterscience Pub!., London-New York-Sydney, p. 46. I964, The Formation of Stars and Galaxies: Unified Hypotheses, in A. Rev. Layzer, D. Astr. Astrophys., Ed. L. Goldberg, 2, p. 341. I965, Problems of Star Formation, I and II, Quart. J.R. astr. Soc., 6; I6I Mestel, L. and 265. Woltjer, L. I965, Dynamics of Gas and Magnetic Fields; Spiral Structure, in Stars and Stellar Systems, 5, Ed. Blaauw and Schmidt, The Univ Chicago Press, Chicago, chap. 23, P·53I. Simon, R. I963, Ann. Astrophys., 26, 456; I964, ibid. 27, I9I. Simon, R. I965, Ann. Astrophys., 28, 40. Lynden-Bell, D. I964, Astrophys. J., 139, I I95· Lin, C. C., Mestel, L., Shu, F. H. I965, Astrophys. J., 142, I43I. Hunter, C. I963, Astrophys. J., 139, 570. McNally, D. I964, Astrophys. J., 140, Io88. Gould, R. J. I964, Astrophys. J., 140, 638. Field, G. B. I965, Astrophys. J., 142, 531. Field, G. B., Saslaw, w. s. I96s, Astrophys. J., 142, s68. Hunter, J. H. I966, Mon. Not. R. astr. Soc., 133, 239· Simoda, M., Kikuchi, S., Unno, W. I966, Publ. astr. Soc. Japan, x8, 31. Kikuchi, S. I966 (in preparation). I964, Sur Ia stabilite gravitationnelle d'un plasma cylindrique anime d'un Tassoul, J. L. mouvement de rotation uniforme, II, Ann. Astrophys., 27, ISO. Simon, R. I965, Sur l'instabilite gravitationnelle d'une couche fluide incompressible en rotation uniforme, Bull. Acad. R. Belgique, Cl. Sci., seme ser., 51, I7o. Simon, R. 1965, Gravitational Instability in a Plane gaseous Medium in non-uniform Rotation, Ann. Astrophys., 28, 626; I966, Gravitational Instability in the Isothermal Stratified Nebula in uniform Rotation (in preparation). Simon, R., Kollasch, C. I966, Instabilite gravitationnelle d'un cylindre non-homogene compressible (in preparation). Toomre, A. I964, Astrophys. J., 139, I2I7. Lin, C. C., Shu, F. H. I964, Astrophys. J., 140, 646; I966, Proc. nat. Acad. Sci., 55, 229. I965, Mon. Not. R. astr. Soc., 130, 97, and I25· Goldreich, P., Lynden-Bell, D. Pacholczyk, A. G., Stodolkiewics, J. S. I963, On the Gravitational Instability of some magnetohydrodynamical Systems of Astrophysical Interest, III, Act .Astr. Pol., 13, 30. Uberoi, C., Raghavachar, M. R. I964, J. ind. lnst. Sci., 46, 91. Strittmatter, P. A. I966, Mon. Not. R. astr. Soc., 131, 491. Strittmatter, P. A. I966, Mon. Not. R. astr. Soc., 132, 359· I966, Astrophys. J., 145, 583. Gliddon, J. E. C. Mestel, L. I966, Mon. Not. R. astr. Soc., 133, 265. Mestel, L., Strittmatter, P. A. I966 (in preparation). Mestel, L., Strittmatter, P. A. Ig66 (in preparation). Mestel, L., Strittmatter, P. A. I966 (in preparation). I966 (in preparation). Mestel, L., Gillis, J.

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34· Mestel, L.

35· 36. 37· 38. 39·

40.

1967, Proc. 14th Internat. Astrophys. Liege Symp., Mem. Soc. R. Sci. Liege, (in press). The 3rd part of this volume is devoted to the formation of stars and further contributions to the problem under review will be found there. Layzer, D. 1963, Astrophys. J., 137, 351. 1964, Astrophys. J., 139, 570. Hunter, C. Nakano, T. 1966, Progr. theor. Phys., 36, 515. Arny, T. T. 1966, Astrophys. J., 145, 572; 1967, Ann. Astrophys. (in press). Arny, T. T. 1966, Astr. J., 71, 377· Imshennik, V. 1., Nadezhin, D. K. 1966, Astr. Zu., (in press); Imshennik, V. 1., Nadezhin, D. K., Pinaev, V. S. 1966, Astr. Zu. 43, 1215; Eminzade, T. A., Gusseinov, 0. Kh. 1964, Izv. Akad. Nauk Azerb. SSR, Ser. Fiz.-Tekn.-Matem. N., no. 4, us.

In closing this report, it is a pleasure to thank all the members of Commission 35 who have kindly communicated information on their work. I am especially grateful to Mrs Massevitch and Dr Hayashi who have prepared very complete surveys of the relevant literature and of work in progress in their respective countries. Finally, I want to acknowledge the efficient help of Drs A. Boury and M. Gabriel in preparing this report. I could not hope to have covered all contributions of significant interest for the Commission and emphasis may not always have been distributed rightly but, omissions or bias certainly were involuntary and I hope that I may count on the forbearance of all. P.

LEDOUX

President de la Commission

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PRESIDENT: Professor Dr K. H. Bi:ihm, Lehrstuhl fur Theoretische Astrophysik, Universitat Heidelberg, Mi:inchhofstrasse 12-14, 69 Heidelberg, Germany. VICE-PRESIDENT: Professor Dr A. B. Underhill, Astronomical Observatory 'Sonnenborgh', Zonnenburg 2, Utrecht, The Netherlands. COMITE o'ORGANISATION: C. de Jager, V. V. Sobolev, R. N. Thomas, H. Van Regemorter, M. H. Wrubel. MEMBRES: Aller (L. H.), Athay, Barbiert, Biermann, Bi:ihm-Vitense, Busbridge, Carson, Cayrel (G.), Cayrel (R.), de Feiter, Edmonds, Elste, Gingerich, Godoli, Gi:ikdogan, Greenstein, Hack, Hardorp, Henyey, Hitotuyanagi, Hotinli, Houtgast, Houziaux, Huang, Hunger, Ivanov, Jefferies, Johnson (H. R.), Kopylov, Kushwaha, Menzel, Mirzojan, Miyamoto, Muller (E. A.), Munch (G.), Mustel, Neveu, Page, Pagel, Peeker (J.-C.), Pecker-Wimel, Petrie (J. K. McD.), Phillips, Pottasch, Rudkji:ibing, Saito (S.), Schatzman, Seaton, Sitnik, Stibbs, Stri:imgen, Swihart, Traving, Ueno, Unno, Unsold, Van t'Veer (Fr.), Vardya, Weidemann, Wright (K.O.), Wyller, Zirker, Zwaan. I.

INTRODUCTION

Commission activity between the assemblies

A conference on the theory of line formation ('Second Harvard-Smithsonian Conference on Stellar Atmospheres') was held in Cambridge, Mass., on 2o-22 January 1965. The meeting was organized by the Smithsonian Astrophysical Observatory and the Harvard College Observatory. A fairly large number of papers were presented. There was a strong emphasis on non-LTE line formation problems for 'few level' atoms. An IAU Colloquium on the 'Blanketing Effect' (organized by this Commission) was held at the Heidelberg University on 17-19 March 1966. Four review papers and 12 shorter communications were presented. The main emphasis of the talks and discussion centered around: (I) The applicability of the present form of the line broadening theory to stellar atmospheres, especially to low density regions. (There was no doubt about the applicability under usual laboratory conditions.) (2) The possibilities of developing a non-LTE line blanketing theory. (3) Statistical methods of treating a very large number of lines in L TE blanketing effect computations. Other symposia related to the theory of stellar atmospheres

They included: An IAU Symposium (no. 26) on 'Abundance Determinations in Stellar Spectra', held in Utrecht, 1o-14 August 1964. This meeting was sponsored by the IAU Commissions 29 and 36. There were sessions on methods of abundance analysis, in which .problems of the theory of stellar atmospheres were discussed. The 5th Symposium on Cosmical Gas Dynamics, held in Nice, September 1965 (IAU Symposium no. 28, sponsored in part by IUT AM) included a very detailed discussion of the hydrodynamics of the solar atmosphere (including convection, convective overshoot, and oscillatory motion) and of atmospheres of pulsating stars. It has been attempted to list the books and the proceedings of symposia which have appeared during the last three years and which are related to the work of this Commission, in section I of the bibliography. 801

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(a) Theory of Radiative Equilibrium

Reviews of radiative transfer problems have been given by D. G. Hummer (37), in Sampson's book (I), and in a very comprehensive way by J. C. Peeker (62, 6I). The problem of constructing good non-grey radiative equilibrium model atmospheres (eventually including non-LTE effects) still plays a fundamental role. The Avrett-Krook method has continued to be used successfully in many applications. A new and very elegant temperature correction procedure has been suggested by L. B. Lucy (48). The most attractive feature of this method is its theoretical simplicity. K. H. Bohm and W. Deinzer (I6) have worked out a Fortran programme of this method and have made the first numerical applications. They found that Lucy's method is a very effective temperature correction procedure, unless the scattering contribution to the source function becomes very strong in most parts of the atmosphere. In the meantime L. G. Henyey (32) has developed a new temperature correction method, which looks very promising, but which has not yet been tested numerically (K. H. Bohm is preparing such a test). Henyey's method is based on the exact conversion of the monochromatic error LJF. into the monochromatic Planck function correction LJB•. Another temperature correction procedure based on a certain type of linearization of the equation of transfer has been suggested by P. Feautrier (28). A simple modification of the Avrett-Krook method has been suggested by T. L. Swihart (70). A combination of an improved flux iteration method and a revised .A-iteration scheme has been worked out by T. Tsuji (74). It has been successfully tested in the case of a picket-fence model. S. Matsushima and Y. Terashita (84) have studied the influence of errors in the absorption coefficient on non-grey models. A useful numerical comparison of non-grey models found by slightly different methods has been given by Gingerich, Mihalas, Matsushima and Strom (3I). K. H. Bohm (IS) found that under certain conditions a temperature inversion can occur in the uppermost layers (where the electron scattering contribution varies rapidly) of very hot non-grey model atmospheres. Since E. Hopf's early work it has been clear that it must be possible to find an exact solution for at least one standard non-grey problem, namely the L TE picket-fence model. This aim has been achieved recently by C. E. Siewert and P. F. Zweifel (6S) and by J. C. Stewart (67). See also J. C. Stewart (68). A considerable amount of research effort is going into the field of non-L TE radiative transfer. R. Wildt (77, 78) is continuing his basic studies of grey non-LTE atmospheres. His approach is based completely on the thermodynamics of the radiation field. He showed that the unattainability of detailed balancing follows from thermodynamics. An interesting approach to the computation of non-LTE atmospheric structure has been suggested by W. Kalkofen (cf. 44). The method permits the numerical computation of the temperature stratification and the radiation field in not too high layers in stellar atmospheres. It is based on the (reasonable) assumption that in deeper layers, in which the important continua are formed, the conditions in the strong lines are already very close to detailed balancing. If that is true the line transfer problem is decoupled from the continuum transfer. A very useful discussion of this approach has been given by D. Mihalas (so). Numerical applications have been made (see Mihalas and Stone (49) and other sections of this report). A general survey of the present state of the non-LTE approach has been given in R. N. Thomas' book (72). He naturally emphasizes line transfer problems (see section II.f of this report), but he also includes the interaction between lines and continua. See also Warner (76).

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A very useful report on the general theory of the emission coefficient has been given by D. G. Hummer (36). A coupled line-continuum transfer problem for a three-level atom has been treated by W. Kalkofen and Avrett (3), Y. Cuny (20), and by Johnson and Klinglesmith (6). A seven-level problem has been solved by T. Kogure (46) in connection with the problem of the Balmer decrement in Be stars. A possible interpretation of the oscillatory phase in novae based on nonL TE effects has been suggested by J .-C. Peeker (63). The non-L TE formation of the Lymancontinuum in an isothermal atmosphere has been studied by R. D. Dietz and L. L. House (86). Non-LTE problems in Wolf-Rayet stars have been considered by Rublev (64). I. Kolesnik and D. A. Frank-Kamenetsky (47) have studied the non-LTE formation of recombination continua in non-stable stars. A related problem has been treated by L. M. Biberman, V. S. Vorobyev and A. N. Lagar'kov (14). Deviations from LTE in a pure hydrogen plasma are treated in (34). The problem of finding the temperature stratification of an atmosphere in the presence of line blanketing has found renewed and strong interest during the last years. Computational programmes incorporating L TE blanketing by many lines have achieved a rather high degree of perfection, largely due to the work of S. E. Strom and his collaborators (cf. S. E. Strom and R. L. Kurucz (85)). 0. Gingerich (89) has studied, under which conditions a schematic treatment is sufficient. There is general agreement that the L TE treatment overestimates the blanketing effect. The question is: How much? R.N. Thomas (73), R. Cayrel (2) and H. Frisch (88) argue that the error is probably very large. The problem could be definitely settled only, if we would understand better the formation of subordinate lines in a stellar atmosphere. A blanketing problem has also been treated by T. L. Swihart (69). Considerable progress has been made in the mathematical theory of radiative transfer. V. A. Ambarzumian has developed a method for applying principles of invariance to nonlinear transfer problems (4, 5). His ideas have been also applied by Nikoghossian to a multi-level line transfer problem (56) and by N. B. Yengibarian (82). Bellman, Kalaba, Kagiwada and Ueno (7, 8, 9, 10, n) have continued to develop the invariant imbedding technique and applied it to a number of problems (e.g. finite slab, one-dimensional medium with a moving boundary). A different procedure of solving transfer problems in a slab geometry has been applied by R. Bellman, H. Kagiwada and R. Kalaba (12). They have (together with S. Ueno) computed graphs of the X- and ¥-functions for a wide range of slab thicknesses and albedos (13). Extensive tables of Chandrasekhar's X- and ¥-functions have also been computed by J. L. Carlstedt and T. W. Mullikin (17). Finite atmospheres with coherent isotropic scattering have been studied by V. V. Sobolev (66) for the limiting case of large optical thickness. He finds that the resolvent of the integral equation determining S(r) can be expressed in terms of quantities characteristic of the semi-infinite atmosphere. J. I. F. King, R. V. Sillars and R. H. Harrison (45) have published tables of Hopf's q-function with 8-digit accuracy. The problem of light scattering in a finite atmosphere has been investigated by V. V. Ivanov (40, 41, 42) and by Ivanov and Leonov (43). He finds an exact solution for the resolvent of the integral equation for the source function in a finite atmosphere. Tables of Ambarzumian's functions for anisotropic scattering have been computed by I. N. Minin, A. G. Piliposian and N. A. Shidlovskaja (52). A small-angle approximation for the source function in certain scattering problems has been discussed by S. Ueno (75). A detailed study of the grey transfer problem with spherical symmetry is due to R. J. Chapman (18). Other problems in the mathematical theory of transfer have been treated by Collins and Code (19), Dave and Walker (21, 22), P. Feautrier (27, 29), Horak and Janousek (35), Hummer

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(38), Irvine (39), Mullikin (87), Nagimer (53, 54, 55), Obridko (57), Pahor and Kuscer (58), Pavlov (59, 6o), Wilson and Sen (79, 8o) and by Yanovitsky (81). The problem of the conversion of the observed centre-to-limb variation into S(T) has been rediscussed (using new mathematical methods) by Delache (23, 24, 25) and by David (83). Delache has also given a qualitative discussion of radiative transfer in an atmosphere with a stellar wind (26). Time-dependent radiative transfer has been investigated by I. N. Minin (51) (in connection with the close binary problem) and by T. L. Swihart (71). A study of wave propagation in a random medium by U. Frisch (30) may permit application to radiative transfer problems.

(b) Continuous absorption coefficients and some other basic data There have been further improvements of the theory of the H--absorption, especially for the free-free transitions. We mention the work by T. L. John (1o, 11, 12), by T. Ohmura (32) and by N. A. Doughty and P. A. Fraser (8). The bound-free transitions of H- have been reinvestigated by Doughty, Fraser and McEachran (7). M. Weinberg and R. S. Berry (36) have drawn attention to the possible importance of a forbidden bound-free continuum of Hincluded by perturbing neighbouring particles in a gas of fairly high density. V. Myerscough's, (34) preliminary results indicate that this forbidden continuum will be of importance in the deeper atmospheric layers of a white dwarf like van Maanen 2 and probably also in the upper transition layer of the solar hydrogen convection zone. There has been a very fast growing interest in the opacity sources in late-type stellar atmospheres. J. R. Auman (1) has succeeded in deriving absorption coefficients due to H 20 for the application to cool stellar atmospheres. A method for estimating the H 20 absorption has been given by M. S. Vardya (23). The problem of the possible importance of negative ions other than H-and H 2 in late-type stars is of considerable interest. It has been studied by Vardya in (26) and in combination with the general problem of molecular abundances in late-type stars in (27, :z8). The Cl--ion shows a rather large abundance in very cool atmospheres (27, 24). The absorption coefficient of Cl- has been computed by R. Kandel (13). V. G. Buslavsky (5) has studied opacity sources in late-type stars in general. The presence of a transmission window at z·65p. in late-type stars has been discussed by Vardya (:zo). In a semi-emperical investigation M. S. Vardya and K. H. Bohm (22) have looked for undiscovered sources of opacity in an M2 main sequence atmosphere. They find that the question could be answered only in a conclusive way, if we could determine the effective temperature with an error not essentially larger than ± IOo°K. K. Kodaira (29) finds that the depression at ..\ 2085 in the solar spectrum can be attributed to the ionization edge of AI I 3p 2P 0 • It has been found that free-free absorption of He- can be very important in hydrogen deficient stellar atmospheres. The He--absorption coefficient has been computed by M. McDowell, M. Williamson and V. Myerscough (15) and by W. B. Sommerville (19). Work on the calculation of absorption coefficients using the quantum defect method has progressed considerably. The papers of G. Peach (16, 33) seem to be especially useful for astrophysical applications. 0. Bely (2) has developed a generalized quantum defect method for hydrogen-like ions. F. Praderie (17) has studied the absorption cross-section for neutral carbon, D. Schluter (35) has developed a somewhat different method and applied it to Ne I, Ar I, Kri and Xe I. New tables of atmospheric opacities have been given by M. S. Vardya (21), A. Cox and J. Stewart (6) and by G. Bode (3).

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Monochromatic atmospheric absorption coefficients have been computed by G. Bode (3) and by J. Baerentzen and E. Mikkelsen (31 ). 0. Gingerich (3o) has given a summary of very useful interpolation formulae for absorption coefficient computations. A description of the simplified treatment of line absorption in blanketing computations is due to Vardya (25). The problem of autoionization and dielectronic recombination in the outer layers of a star has continued to receive considerable attention. We mention the work of A. Burgess (cf. 4), L. Goldberg, A. K. Dupree and J. W. Allen (9) and W. van Rensbergen (18). The excitation of H-atoms by protons has been studied by McCarrol and Salin (q).

(c) Hydrodynamic Phenomena in Stellar Atmospheres The proceedings of the Joint Discussion on this subject have been published in Transactions !AU, 12B, 531. Hydrodynamic problems of stellar atmospheres have been also discussed at the Nice symposium (see section I of this report). Convection, Turbulence:

E. A. Spiegel (43, 44) summarized the present possibilities for a physical theory of turbulent convection in the Boussinesq approximation. A general survey of the available data on models of the solar hydrogen convection zone has been given by K. H. Bohm (4). He has also discussed convection overshoot at the upper (4) and lower (4, 6) boundaries of the convection zone. The latter problem has been recently investigated by K. Kohl (55). The physical mechanism of convective penetration has been discussed by D. W. Moore (31). The possible importance of convective overshoot for the atmospheric Lithium depletion has been studied by R. W eymann and R. L. Sears (50) and by Bohm (6). The general problem of convective dilution of elements has been studied by E. Schatzman (39). Problems of the outer convection zone in connection with the specification of the outer boundary conditions for internal structure calculations have been discussed by L. H. Henyey, M. S. Vardya and P. Bodenheimer (13) and by J. Faulkner, K. Griffiths and F. Hoyle (10). A semiempirical discussion of stellar convection zones has been given by 0. C. Wilson (51). D. Mihalas (29) has treated the transition region between a nongrey radiative equilibrium atmosphere and a convection zone described by the mixing length theory. A related problem has been studied by N. Sack (37). K. Bi:ihm (5) has suggested that M-dwarf atmospheres may show an observable deviation from a radiative equilibrium stratification due to the fairly large convective energy transport in these atmospheres. Swihart and Margrave (45) are studying inhomogeneities in the solar atmosphere. Very interesting work on the deformation of magnetic fields by convection has been done by N. 0. Weiss (48, 49). K. Walter (47) has proposed a very unconventional theory of the outer solar convection zone. Polytropic atmospheres are still a very useful tool for studies of convection in compressible atmospheres: E. A. Spiegel (42) has investigated convective instability in such atmospheres using a perturbation treatment with respect to layer thickness. As an alternative he has explored a variational approach and the WKB approximation. The onset of convection in a polytropic atmosphere with a uniform magnetic field has been studied by S. A. Kaplan and N. S. Petrukhin (17). They have derived a simple instability criterion for this case. A generalization of the Schwarzschild criterion for an atmosphere with a magnetic field has been discussed by D. 0. Gough and R. J. Taylor (12). A. Baglin (1) has generalized the Schwarzschild criterion for the case in which a separation of elements occurs in a strong gravitational field. S. Yamaguchi (52) used a variational technique to study the convective instability in a layer with depth

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dependent superadiabatic gradient. Limitations of the applicability of the Schwarzschild criterion have been discussed by G. F. Sitnik (40). W. Deinzer (7) has used the suppression of convection by a magnet field in a heuristic way to construct a magnetohydrostatic model of a sunspot. Convective overstability in a geometrically thin medium with a superadiabatic gradient has been investigated by S. Kato (18). A simple model permitting a physical explanation of overstability has been developed by D. W. Moore and E. A. Spiegel (32). J. Baerentzen (2) has given new formulae for the computation of the adiabatic gradient and the specific heat. Turbulence in stellar atmosphere has been discussed by Hollandsky (15), Hollandsky and Chub (16), I. M. Kopylov (22), P. E. Nissen (33) and E. C. Olson (34, 35). 0. P. Hollandsky (14) has discussed the possible influence of the radiation pressure on the sound velocities in the atmospheres of hot supergiants. Oscillations

Considerable attention has been paid to the problem of the generation of the photospheric oscillation or waves by the granulation. M. J. Lighthill (25) has given a very comprehensive and illuminating survey of this problem. S. Kato (19) has investigated atmospheric oscillations excited by turbulence near the critical frequency. He has also studied (20, 21) the response of an unbounded atmosphere to a point disturbance. F. Meyer and H. U. Schmidt (28) have made extensive computations of the response of the solar atmosphere to a granular disturbance. P. Souffrin (41) has studied the variation of hydrodynamic waves with distance from the hydrogen convection zone. He has generalized diagnostic diagrams for an isothermal atmosphere to include radiative dissipation. He finds that gravity waves should be unimportant in the photosphere because of their strong radiative damping. A standing-mode gravity wave in the chromosphere has been studied by Y. Uchida (46). Empirical data on photospheric oscillations have been gathered, reduced and interpreted in a very careful way by F. N. Edmonds (8, 9), by P. Mein (27) and by J. B. Zirker (53). A very interesting new observational study of the velocity fields in the photosphere has been made by E. Frazier (56). He finds a definite splitting of the maximum of the oscillation power spectrum into two peaks. He was also able to detect convective overshoot into the uppermost layers of the photosphere. Other problems Heating of an atmosphere by shock waves has been investigated by G. A. Bird (3), by M. Kuperus (57) and by M. Saito (38). The propagation and coupling between the three magnetohydrodynamic modes in a stratified medium has been studied by U. Frisch (n). S. V. Rublev (36) has investigated the dynamics of Wolf-Rayet atmospheres. An important empirical study of the mass loss of T-Tauri stars is due to L. Kuhi (23). Other hydrodynamic problems have been treated by Lemaire (24), McLean (26), and Grover and Hardy (54). (d) Thermodynamic Problems of Stellar Atmospheres

In this section we shall discuss very briefly only those papers which have not yet been considered in connection with either the computation of absorption coefficients or with the convection problem. B. Schlender and G. Traving (3) have shown that the approximate computation of partition functions can be greatly simplified if one uses a Chebyshev approximation. Applications of

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this method can be found in the paper by G. Traving, B. Baschek and H. Holweger (5). The problem of pressure dissociation and its influence on molecular partition functions has been investigated by M. S. Vardya (7, 9). He has also (8) computed some basic thermodynamic quantities for a mixture of H, He and 16 other elements (with solar photospheric abundance ratios) allowing for different stages of ionization and the formation of H 2, Ht and H-. Molecular abundances in stellar atmospheres have been calculated by Tsuji (6), by Wyller and Morris (1o) and by J. F. Dolan (1). Wyller and Morris have studied 15 diatomic and 16 triatomic types of molecules in the atmospheres of carbon stars. Dolan and Vardya (Ref. 27, Section (b)) has also paid special attention to polyatomic molecules. Nonequilibrium ionization in an atmosphere due to the ejection of 'plasma bunches' has been considered by I. G. Kolesnik (2). Studying the importance of inelastic collisions, S. Souffrin (4) has reached the conclusion that in normal stellar chromospheres there will be no observable deviation from the Maxwellian distribution of particles. (e) Extended Envelopes

Most of the work done in this field belongs either to the subject of other commissions or has been treated in other sections of this report. In this section we have just listed a few references, which otherwise could not be easily fitted into our classification scheme. These papers contain discussions of (a) the influence of the solar wind on abundance determinations in the solar corona (J. C. Brandt, 1), (b) problems of expanding stellar envelopes (Gorbatzky, 2) (c) a study of shells of Be stars (Lacoarret, 4, (d) the extended chromosphere of 3 I Cygni (Magnan, 7) and (e) a few problems of solar and stellar chromospheres and coronas (Hughes, 3; Livshitz, 5; Livshitz and Nikolsky, 6; and Athay, 8). (/)General Theory of Line Profiles and Line Formation

Problems of the physical theory of the line absorptions coefficient mostly belong to the field of Commission 14· I shall mention only a few references to work being done by Commission members or to papers related to this work. A very useful survey of the theory of line broadening and its astronomical applications has been given by H. van Regemorter (47). The same author (together with S. Bn!chot, 46) has derived a generalization of the impact broadening theories of Lindholm and of Baranger, taking into account (among other effects) inelastic collisions. H. Pfennig (38) and H. Pfennig, E. Trefftz and C. R. Vidal (39) have drawn attention to the fact that until recently the KolbGriem Stark broadening theory had not been tested in the laboratory in the density range which is of interest in the theory of most stellar atmospheres. Recent experiments of Ferguson, Schluter and Vidal in the range Ne ~ 1013 cm- 3 give (according to Pfennig, Trefftz and Vidal, 39) results which are much closer to the quasistatic theory than to the Kolb-Griem theory. The theoretical reason for this result is not yet understood. The Stark broadening functions for the hydrogen lines have been recomputed by F. N. Edmonds, H. Schluter and D. C. Wells (16). They take into account the effects of correlation and shielding. The results are represented graphically for the Lyman-Balmer-Paschen- and Brackett-lines up to n = 18. The problem of determining the electron density from line merging due to Stark effect has been reinvestigated by L. N. Kurochka (29) and C. R. Vidal (49). Kurochka (30) has also considered the possible influence of the Doppler effect on line merging. The Influence of Stark broadening on abundance determinations has been studied by D. Mugglestone and B. J. O'Mara (32). New Computations of Voigt functions are due to C. Chiarella and A. Reichel (12). A general survey of stellar atmospheres and their line spectra has been given by K. 0. Wright (51). A series of papers on the measurements of lifetimes of excited levels has been introduced by E. Schatzman (41). U2

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The following work has been done on LTE line formation (mainly in connection with the problem of atmospheric abundance analysis): Baschek, Holweger and Traving (9) have published their Algol programme for the quantitative analysis of stellar spectra. This programme has been translated into Fortran by Peytremann (55). 'Differential curves of growth' have been discussed by Baschek and Traving (10). They have published tables and graphs of the derivatives of Unsold's curve of growth. Pagel has applied the differential curve of growth method (37). F. N. Edmonds (17) has compared curves of growth and contribution curves for the same line, but for different fine analysis methods. Mugglestone and O'Mara (31) have considered the influence of saturation effects on the abundances derived from faint and medium-strong lines. They especially discuss the determination of the oxygen and notrogen abundance in the solar photosphere. A very useful and interesting theoretical study of the broadening of lines by the presence of a turbulent velocity field has been made by G. Traving (44). He has investigated in quantitative detail the influence of the scale of the hydrodynamic motion on the curve of growth. 'Microturbulence' and 'macroturbulence' in the usual sense appear as limiting cases in his theory. Y. Yamashita (52) has studied the curve of growth for lines formed by pure absorption in an atmosphere where S(T) has a linear + exponential depth dependence and where (t I000°K). Shuter and Verschuur (1964) studied the three strongest sources with a high frequency resolution, and also found evidence for cool absorbing clouds. Absorption studies have been made of a number of individual sources, mainly for distance determination. These are the Omega nebula (Bystrova et al. 1963a, 1964a), Tycho's supernova (Menon and Williams 1966), W 49 (Akabane and Kerr 1965), several other Westerhout sources examined by Bystrova et al. (1963b, 1964b, 1965), and 3C 273 (Robinson et al. 1963; Williams 1965). Absorption in the galactic centre region has been studied by Egorova (1963, 1964), Ryzhkov et al. (1964), and Kerr (1966a). In this region there are several continuum components, and the absorption pattern is quite complicated. One theoretical study has been published (Smith 1964), on the absorption profiles to be expected for an expanding HI cloud. No further observations have been published of the Zeeman effect in interstellar hydrogen. The conclusion from work carried out so far is that the magnetic field inside absorbing hydrogen clouds is less than 5 x 10-6 gauss. A number of precise measurements have been reported for the frequency of the hyperfine transition of ground-state atomic hydrogen. The most recent determinations are those by Beehler et al. (1966), Johnson and McGunigal (1966), Peters et al. (1965), and Ramsey (1965). A mean of their results gives a free-space value of: 1420 405

751·786 ± o·o1 Hz,

corrected to zero magnetic field and zero absolute temperature. 2.

Hydroxyl Lines

The outstanding development in radio line studies in the last three years has been the detection of the group of four .A-doubling lines near 18 em produced by interstellar OH radicals. A recent review has been given by Robinson (1966). The lines have been observed both in absorption and emission, and many unexpected results have been reported. The first discovery was made by Weinreb, Barrett, Meeks, and Henry (1963), who found the 1665 and 1667 MHz lines in absorption in the spectrum of Cassiopeia A. Other early absorption observations were made by Bolton et al. (1964a), Dieter and Ewen (1964), Weaver and Williams (1964), and Barrett, Meeks, and Weinreb (1964); the values reported for line strengths and shapes were approximately as expected. Detailed studies of OH absorption effects in and around the direction of Sagittarius A revealed the existence of intense concentrations of OH in the galactic centre region, (Robinson et al. 1964; Goldstein et al. 1964; Bolton et al. 1964b; Bystrova et al. 1964). The strength of the absorption in this region led to the detection of the other two lines of the group at 1612 and 1720 MHz (Gardner et al. 1964). The intensity ratios between the four lines were found to be generally lower than expected theoretically, and to vary considerably from point to point over the region. The distribution of OH in the central region is quite different from that of the hydrogen. Some reasons for the observed systematic increase in the relative abundance of OH towards the galactic nucleus have been suggested by Carroll and Salpeter (1966). OH emission was not at first detected, but in observations with a narrow-band receiver Weaver et al. (1965) discovered some very narrow emission lines in a number of sources Further observations by Weinreb et al. (1965), Zuckerman et al. (1965), McGee et al. (1965)

RADIOASTRONOMIE

881

and Weaver et al. (1966) showed the great complexity of the emission phenomena. Narrow lines are emitted in very localized portions of H II regions, often near their peripheries. The intensity ratios of the four lines of the group are highly variable from source to source, and even from one emission component to another in the same source, clearly indicating nonequilibrium populations. Linear polarization of many of the emission components has been reported by Weinreb et al. (1965), Zuckerman et al. (1965), Davies et al. (1966), and Williams et al. (1966). Circular polarization has also been found in some sources by Davies et al. (1966), and Barrett and Rogers (1966a). The polarization is often very strong, with great differences in degree and direction for neighbouring emission components. A simple Zeeman interpretation is not able to account for the observed phenomena. Possible interpretations have been proposed by Meeks et al. (1966), Verschuur (1966) and Cook (1966b). Interferometric studies by Rogers et al. (1966) and Cudaback et al. (1966) have shown that some OH emission features have an angular size well under one minute of arc; consequently their brightness temperatures must be very high. Dieter et al. (1966) have reported secular variations in individual emission components in two sources over a period of a few weeks. These results have not yet been confirmed by other workers. The basic theory of OH absorption and the early observations was reviewed by Barrett (1964). Attempts have been made to explain the anomalous emission phenomena in terms of a maser action in which population inversion is produced by ultraviolet or infrared radiation (Cook 1966a; Shklovskii 1966; Perkins, Gold, and Salpeter 1966). Symonds (1965) discussed the anomalous intensities in terms of the abnormal formation of OH molecules through a process involving negative oxygen ions. Precise laboratory frequency measurements have been reported for the four lines by Radford (1964), while Powell and Lide (1965) have made an improved measurement of the OH dipole moment. Goss and Weaver (1966) have calculated improved values for the Einstein A coefficients. The possibility of detecting lines from other isotopic species of OH has been discussed by Barrett and Rogers (1964), and the radio detection of interstellar 0 18H 1 has recently been announced (Barrett and Rogers 1966b).

3· Hydrogen and Helium Recombination Lines Kardashev predicted in 1959 that high-excitation lines of hydrogen should be detectable in H II regions. The first observation of such a line was made by Dravskikh et al. (196¥, 1964-h, 1965), who detected an emission line at 5763 MHz, corresponding to the transition n = 105 ton = 104, in the Omega nebula. On more recent usage, this is called the H 104 a: line. The most extensive work has been done on the H 109 a: line at 5009 MHz, which has been detected in emission from sixteen sources, for which distances, Doppler widths and electron temperatures have been determined (Hoglund and Mezger 1965a, b; Mezger 1966; Mezger and Hoglund 1966). Other lines that have been reported are H go a: (Sorochenko and Borodzich 1965), H 156 a: and H 158 a: (Lilley et al. 1966a), and H 166 a: (Palmer and Zuckerman 1966). In addition, three lines from neutral helium, He 156 a:, He 158a:, and He 159 a:, have been detected by Lilley et al. (1966b). The derivation of electron temperatures and other parameters from observations of these lines has been discussed by Sorochenko (1965) and Goldberg (1966). A table of frequencies for the hydrogen series has been computed by Pulley and Shuter (1966). The detection of the recombination lines has provided a new method for the study of ionized regions, and also a new approach to the large-scale kinematics of the Galaxy.

882

COMMISSION 40 4· Other Lines

Encouraged by the unexpected strength of the OH lines, several workers have attempted to detect the CH line near 10 em wavelength, but no detailed accounts have yet been published. One major difficulty has been the uncertainty of the line frequency, for which new determinations have been given by Douglas and Elliott (1965) and Goss (1966). The electric dipole moment of the ground electronic state of CH has been measured by Phelps and Dalby (1966). Malville (1964) has discussed the possibility of detecting two lines near 5 and 6 em from metastable hydrogen molecules. General reviews of other line possibilities have been published by Robinson and McGee (1965) and Kerr (1966).

BIBLIOGRAPHY

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Bok, B. J, I964, Galactic and Extragalactic Structure, pp. 75, Tata Inst. Fundamental Res., Bombay. Dieter, N. H., Goss, W. M. I966, Rev. mod Phys., 38, 256-297. I965, Distribution of Interstellar Hydrogen, in Galactic Structure, Kerr, F.]., Westerhout, G. Eds. Blaauw, A., Schmidt, M., Univ. of Chicago Press, Chicago, Chap. 9, pp. I67-202. I966, Chap. I2 in Nebulae and Interstellar Matter, Vol. 7 of Stars and Stellar Kerr, F. J. Systems, Ed. Kuiper, G. P., Middlehurst, B. M., Univ. of Chicago Press, Chicago (in press). Oort, J. H. I965, Trans. !AU, I2A, 789. Westerhout, G. I964, IEEE Trans. Ant Propag, AP-I2, 954-963. 21-cm

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Agekyan, T. A., Petrovksaya, I. V., Fesenko, B. I. I964, Astr. Zu., 4I, I027 = I965, Soviet Astr., S, 823. Akabane, K., Kerr, F. J. I965, Austr. J. Phys., IS, 91. Ariskin, V. I. I965, Astr. Zu., 42, 939 = I966, Soviet Astr., 9, 722. Avner, C. I964, Ph.D. thesis, Univ. Illinois. Balazs, B. I965, Z. Astrophys., 62, 6. Becker, W. I964, Z. Astrophys., gS, 202. Beehler, R. and 11 others. I966, Proc. Inst. electr. electron. Eng., 54, 301. Behr, A. I965, Z. Astrophys., 62, I57· Blaauw, A., Tolbert, C. R. I966, Bull. astr. Inst. Nether!., IS, 405. Blaauw, A. I966, IAU Symp. no. JI (in press). Brodskaya, E. S. I963, Izv. Krym. astrofiz. Obs., 30, I26. Burton, W. B. I966, Bull. astr. Inst. Nether!., IS, 247. Bystrova, N. V., Gosachinskii, I. V., Egorova, T. M., Ryzhkov, N. F. I963a, Astr. Tsirk., no. 244, 1. Bystrova, N. V., Gosachinskii, I. V., Egorova, T. M., Ryzhkov, N. F. I963b, Astr. Tsirk., no. 269, I. Bystrova, N. V., Gosachinskii, I. V., Egorova, T. M., Ryzhkov, N. F. I964Q, lzv. glav. astr. Obs. Pulkove, 23, I I I . Bystrova, N. V., Gosachinskii, I. V., Egorova, T. M., Ryzhkov, N. F. I964b, Izv. glav. astr., Obs. Pulkove, 23, I I6. I964, Astr. Tsirk., no. 307, 1. Bystrova, N. V., Gosachinskii, I. V., Ryzhkov, N. F. Bystrova, N. V., Gosachinskii, I. V., Egorova, T. M., Ryzhkov, N. F. I965, Izv. glav. astr. Obs. Pulkove, 24, 202. Clark, B. G. I965, Astrophys. J., I42, I398. Dalgarno, A., Rudge, M. R. H. I964, Astrophys. J., I4o, 8oo. Davies, R. D., Tovmassian, H. M. I963, Mon. Not. R. astr. Soc., I27, 45·

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I964, Astr. J., 69, 288. Dieter, N. H. I965, Astr. J., 70, 552. Dieter, N. H. I963, Astr. Zu., 40, 382 = Soviet Astr., 7, 290. Egorova, T. M. I964, lzv. glav. astr. Obs. Pulkove, 24, 77· Egorova, T. M. I965, Z. Astrophys., 6I, 273. Elwert, G., Hablick, D. I965, Astrophys. J., I42, I645· Feast, M. W., Thackeray, A. D. I966, Astrophys. J., I45o 79· Garzoli, S. L., Varsavsky, C. M. I964, Izv. Krym. astrofiz. Obs., 3I, IOO. Gershberg, R. E. I964, Z. Astrophys., 59, 83. Girnstein, H. G., Rohlfs, K. I964a, Astrophys. J., I40, 802. Goldstein, S. ]. I964b, Proc. Inst. electr. electron. Eng., 52, I046. Goldstein, S. ]. I966, Astr. J., 7I, 297· Goldstein, S. ]., Welch, B.]. I965, Astr. Zu., 42, 929 = I966, Soviet Astr., 9, 7I4. Gosachinskii, I. V. I966, Astr. Zu., 43, 284. Gosachinskii, I. V. I965, Kleinheubacher Berichte, Io, 205. Grahl, B. H. I964, Astr. Zu., 4I, I85 = Soviet Astr., 8, I39· Grigoreva, N. B. I965, Izv. Krym. astrofiz. Obs. 34, 238. Grigoreva, N. B. I966, Bull. astr. Inst. Netherl., I8, 323. Habing, H. ]. I966, Ph.D. thesis, Princeton Univ. Heiles, C. I964, Publ. astr. Soc. Pacific, 76, 354· Hill, G., Kerr, F. J. I963, Astrophys. J., I38, 988. Howard, W. E., Wentzel, D. G., McGee, R. X. I965, Astr. J., 70, 679. Howard, W. E., Westerhout, G. I966, Bull. astr. Inst. Nether[., I8, 4I3. Hulsbosch, A. N. M., Raimond, E. I966, Astrophys. J., I43o I53· Innanen, K. A. I966, U.S. NASA Tech. Note TN D-3292. Johnson, E. E., McGunigal, T. E. I964, Astr. Zu., 4I, 6oi = I965, Kardashev, N. S., Lozinskaya, T. A., Sleptsova, N. F. Soviet Astr., 8, 479· I966a, IAU Symp. No. 3I (in press). Kerr, F.]. I966b, IAU Symp. No. 3I (in press). Kerr, F. ]. I966, Austr. J. Phys., I9, 75· Komesaroff, M. M. I965, Astr. Zu., 42, 537 = I966, Soviet Astr., 9, 426. Kostyakova, E. B. I966a, Bull. astr. lnst. Nether[. Suppl., I, 77· Lindblad, P. 0. I966b, IAU Symp. No. 3I (in press). Lindblad, P. 0. I964a, Astrophys. J., I39o Io66. Locke, J. L., Galt,]. A., Costain, C. H. I964b, Astrophys. J., I39o I07I. Locke, J. L., Galt,]. A., Costain, C. H. I964, Soobfc. gos. astr. lnst. P.K. Sternberga, no. I3I, 37· Lozinskaya, T. A., Kardashev, N. S. I964, Astr. Tsirk, no. 299, I. Lozinskaya, T. A. 1965, Mon. Not. R. astr. Soc., I29, 299· Lynden-Bell, D. I964, Astr. Zu., 4I, 6o8 = I965, Soviet Astr., 8, 485. Makarova, S. P. I965, Astr. Nachr, 288, I55· Marx, S. I965, Ric. astr. Specola astr. Vatic., 7, I77· McCarthy, M. F., Treanor, P. ]. I964, Austr. J. Phys., I7, 128. McGee, R. X., Milton, J. A. I966, Austr. J. Phys. Suppl. no. I, I-II. McGee, R. X., Milton, J. A., Wolfe, W. I965, Nature, 207, I79· Meaburn, J. I966, Astr. J., 7I, 392. Menon, T. K., Williams, D. R. W. 1964, Astr. J., 6g, 95· Muhleman, D. 0., Walker, R. G. 1966, Bull. astr. Inst. Nether[. Muller, C. A., Raimond, E., Schwarz, U. J., Tolbert, C. R. Suppl., I, 2I3. I964, Astrophys. J., I40, I62. Miinch, G., Miinch, L. I964, Verslag Afd. Nat., Kon. Nederl. Akad. Wet., Amsterdam, 73, 94· Oort, ]. H. I966a, Trans. !AU, I2 B, 395· Oort, J. H. I966b, Bull. astr. Inst. Nether[., I8, 42I. Oort, J. H. I966c, IAU Symp. No. 29 (in press). Oort, J. H. I966d, IAU Symp. No. 3I (in press). Oort, J. H. I966, Astr. Zu., 43, 40 = Soviet Astr., IO, 30. Pavlovskaya, E. D., Sharov, A. S. I965, Appl. Phys. Lett., 7, 34· Peters, H. E., Holloway, J., Bagley, A. S., Cutler, L. S.

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Prata, s. w. 1964, Bull. astr. Inst. Netherl., I7, 5II. Pronik, I. I. 1963, Izv. Krym. astrofiz. Obs., 30, n8. Pronik, I. I. 1965, Astr. Zu., 42, 923 = 1966, Soviet Astr., 9, 709. Pskovskii, Y. P. 1965, Astr. Zu., 42, n84 = 1966, Soviet Astr., 9, 919. 1966a, Bull. astr. Inst. Netherl., I8, 191. Raimond, E. Raimond, E. 1966b, Bull. astr. Inst. Nether[. Suppl., I, 33· Ramsey, N. F. 1965, Metrologia, I, 7· Rickard,].]. 1965, Astr. J., 70, 688. 1966, Ph.D. thesis, University of Maryland. Riegel, K. W. Robinson, B.]., van Damme, K. ]., Koehler,]. A. 1963, Nature, I99, 990. 1966, Astrophys. J. (in press). Robinson, B.]. Rohlfs, K. 1963, Mitt. astr. Ges., p. 122. Rohlfs, K. 1964, Z. Astrophys., 59, 102. 1966, Z. Astrophys., 63, 207. Rohlfs, K. 1964, Bull. astr. Inst. Nether[., I7, 381. Rougoor, G. W. 1964, Izv. glav. astr. Ryzhkov, N. F., Egorova, T. M., Gosachinskii, I. V., Bystrova, N. V. Obs. Pulkove, 23, 3· 1965, Rotation Parameters and Distribution of Mass in the Galaxy, in Galactic Schinidt, M. Structure, Eds. Blaauw, A., Schmidt, M., Univ. of Chicago Press, Chicago, Chap. 22, pp. 513-530. 1966, Bull. astr. Inst. Nether[., I8, 263. Shane, W. W., Bieger-Smith, G. P. Shuter, W. L. H., Verschuur, G. L. 1964, Mon. Not. R. astr. Soc., I27, 387. Smith, A. 1964, Mon. Not. R. astr. Soc., 127, 347· Smith, G. P. 1963, Bull. astr. Inst. Nether[., I7, 203. Takakubo, K. 1963a, Sci. Rep. Tohoku Univ., First Ser., 47, 65. 1963b, Sci. Rep. Tohoku Univ., First Ser., 47, 108. Takakubo, K. Terauti, R. 1963, Sci. Rep. Tohoku Univ., First Ser., 47, I 14. 1966, IAU Symp. No. 31 (in press). Tovmassian, H. M. van Woerden, H. 1963, Astr. J., 68, 296. 1966, Trans. !AU, 12 B, 391. van Woerden, H. 1965, Ann. Astrophys., 28, 1008. Viennot, L. Westerhout, G. 1966, The Maryland-Green Bank galactic 21-cm line survey, first edition. Univ. Maryland. 1963, Astr. Notes, no. 8, 2o-31. Wilhelmsson, H., Winnberg, A. 1965, Galactic Interstellar Absorption Lines in the Spectrum of 3C273 Williams, D. R. W. in Quasi-Stellar Sources and Gravitational Collapse, Ed. Robinson, I., Schild, A., Schiicking, E. L., Univ. of Chicago Press, Chicago, Chap. 14, pp. 213-217. Zasov, A. V. 1965, Astr. Zu., 42, 959· Zhu Ci-Sheng 1964, Acta astr. Sin., 12, II3.

Hydroxyl Lines Barrett, A. H., Meeks, M. L., Weinreb, S. 1964, Nature, 202, 475· Barrett, A. H., Rogers, A. E. E. 1964, Nature, 204, 62. 1964, IEEE Trans. Ant. Propag., AP-12, 822. Barrett, A. H. Barrett, A. H., Rogers, A. E. E. 1966a, Nature, 2IO, 188. 1966b, IAU Symp. No. 31 (in press). Barrett, A. H., Rogers, A. E. E. Bolton,]. G., van Damme, K. ]., Gardner, F. F., Robinson, B.]. 1964a, Nature, 20I, 279. Bolton, J. G., Gardner, F. F., McGee, R. X., Robinson, B. ]. 1964b, Nature, 204, 30. 1964, Astr. Tsirk., no. Bystrova, N. V., Egorova, T. M., Ryzhkov, N. F., Barrett, A. H. 310, 5· Carroll, T. 0., Salpeter, E. E. 1966, Astrophys. J., I43, 609. 1966a, Nature, 2IO, 611. Cook, A. H. 1966b, Nature, 2II, 503. Cook, A. H. 1966, Phys. Rev. Lett., I7, 452. Cudaback, D. D., Read, R. B., Rougoor, G. W.

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1966, Nature, 209, 974· Davies, R. D., de Jager, G., Verschuur, G. L. 1964, Nature, 201, 279· Dieter, N. H., Ewen, H. I. 1966, Astr. J., 71, 160. Dieter, N. H., Weaver, H., Williams, D. R. W. 1964, Phys. Rev. Lett., Gardner, F. F., Robinson, B.]., Bolton, F. G., van Damme, K. J. 13, 3· 1964, Nature, 203, 65. Goldstein, S. ]., Gundermann, E. ]., Penzias, A. A., Lilley, A. E. 1966, Astr. J., 71, 162. Goss, W. M., Weaver, H. 1965, Nature, 208, 1193. McGee, R. X., Robinson, B.]., Gardner, F. F., Bolton, J. G. 1966, Science, 153, 978. Meeks, M. L., Ball, J. A., Carter, J. C., Ingalls, R. P. 1966, Astrophys. J., 145, 361. Perkins, F., Gold, T., Salpeter, E. E. 1965, J. chem. Phys., 42, 4201. Powell, F. X., Lide, D. R. 1964, Phys. Rev. Lett., 13, 534· Radford, H. E. 1964, Nature, :zo:z, 989. Robinson, B. ]., Gardner, F. F., van Damme, K. ]., Bolton, J. G. 1966, IAU Symp. No. 31 (in press). Robinson, B.]. Rogers, A. E. E., Moran, J. M., Crowther, P. P., Burke, B. F., Meeks, M. L., Ball, J. A., Hyde, 1966, Phys. Rev. Lett., 17, 450. G. M. 1966, Astr. Tsirk., no. 372. Shklovskii, I. S. 1965, Nature, 2o8, 1195. Symonds, J, L. 1966, Observatory, 86, 55· Verschuur, G. L. 1964, Nature, 201, 380. Weaver, H. F., Williams, D. R. W. 1965, Nature, 208, 29. Weaver, H. F., Williams, D. R. W., Dieter, N. H., Lum, W. T. 1966, Astr. J., 71, 184. Weaver, H. F., Williams, D. R. W., Dieter, N. H. 1963, Nature, :zoo, 829. Weinreb, S., Barrett, A. H., Meeks, M. L., Henry, J. C. 1965, Nature, Weinreb, S., Meeks, M. L., Carter, ]. C., Barrett, A. H., Rogers, A. E. E. 2o8, 440. 1966, Astr. J., 71, 186. Williams, D. R. W., Dieter, N. H., Weaver, H. 1965, Nature, 208, 441. Zuckerman, B., Lilley, A. E., Penfield, H.

Hydrogen and Helium Recombination Lines 1964Q, Astr. Tsirk., no. 282, :z. Dravskikh, Z. V., Dravskikh, A. F. 1964b, Astr. Tsirk, no. 305, 2. Dravskikh, Z. V., Dravskikh, A. F., Kolbasov, V. A. Dravskikh, A. F., Dravskikh, Z. V., Kolbasov, V. A., Misezhnikov, G. S., Nikulin, D. E., 1965, Dokl. Akad. Nauk SSSR, 163, 332. Shteinshleiger, V. B. 1966, Astrophys. J., 144, 1225. Goldberg, L. 1965a, Science, 150, 339, 347· Hoglund, B., Mezger, P. G. 1965b, Astr. J., 70, 678. Hoglund, B., Mezger, P. G. 1966a, Nature, 209, 468. Lilley, A. E., Menzel, D. H., Penfield, H., Zuckerman, B. 1966b, Nature, 211, 174. Lilley, A. E., Palmer, P., Penfield, H., Zuckerman, B. 1966, Astr. J., 71, 171. Mezger, P. G. 1966, Astrophys. J. (in press). Mezger, P. G., Hoglund, B. 1966, Nature, 209, 1118. Palmer, P., Zuckerman, B. 1966, Can. J. Phys., 44, 1663. Pulley, H. C., Shuter, W. L. H. 1965, Trudy fiz. Inst. Akad. Nauk SSSR, 28, 90. Sorochenko, R. L. 1965, Dokl. Akad. Nauk SSSR, 163, 603. Sorochenko, R. L., Borodzich, E. V.

Other Lines 1965, Can. J. Phys., 43, 496. Douglas, A. E., Elliot, G. A. 1966, Astrophys. J., 145, 707. Goss, W. M. 1966, Chap. 12 in Nebulae and Interstellar Matter, Vol. 7 of Stars and Stellar Kerr, F. J. Systems, Eds. Kuiper, G. P., Middlehurst, B. M., Univ. of Chicago Press, Chicago, (in press). 1964, Astrophys. J., 139, 198. Malville, ]. M. 1966, Phys. Rev. Lett., 16, 3· Phelps, D. H., Dalby, F. W. 1965, lnf. Bull. Southern Hemisphere, no. 6, 37· Robinson, B.]., McGee, R. X.

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E. EXTRAGALACTIC RADIO ASTRONOMY: COSMOLOGY

(Prepared by I.

J.

R. Shakeshaft)

General Remarks

The past three years have seen considerable progress in studies of extra-galactic radio sources, with the completion of large-scale surveys in both hemispheres, with improvements in positional accuracies and, consequently, the number of optical identifications, and with advances in knowledge of the spectra, brightness distributions and polarization of sources. Our understanding of these phenomena, however, remains rudimentary and it is not yet clear at the time of writing, for instance, what relationship, if any, exists between quasi-stellar sources (QSS) and radio galaxies, nor even whether the QSS are local objects or at cosmological distances. The situation as of December 1963 is described at length in the proceedings of the first Texas Symposium (Robinson et al. 1965). Other reviews include those by Priester and Rosenberg (1964), Bolton (1965), Ryle (1966), Schmidt {I966), Smith, H. J. {I966), and Burbidge, E. M. {I967). The proceedings of the NASA Symposium held in New York in December I962 have been edited by Maran and Cameron {I964). 2.

Surveys, accurate positions and identifications

All the information available in May I964 on 1292 discrete sources was collated by Howard and Maran {I965), but since then Pauliny-Toth, Wade and Heeschen {I966) have used the N.R.A.O. 92 m antenna to check the 3C survey, the 4C survey has been completed in two parts (Pilkington and Scott I965, Gower et al. I967) with a total of 4843 sources in the range - 05° < 8 < + 8o0 and having flux densities > 2 x Io- 26 w m- 2 Hz-1 at I78 MHz, and the Parkes catalogue has been published in four parts (Bolton et al. I964, Price and Milne 1965, Day et al. I966, Shimmins et al. 1966a) with a total of 1673 sources in the range - 90° < 8 < + 20°. Further surveys have been carried out by Heeschen and Wade {I964) to determine the radio emission from bright galaxies, by Braccesi et al. (1965) at 408 MHz for the range - 30° < 8 < - 20°, by Davis et al. (1965) at 400 MHz, by Kellermann and Read (1965) at I421 MHz which is, so far, the highest frequency at which a substantial area of sky has been surveyed in detail, by MacLeod et al. (1965) at 6Io·5 MHz, by Dixon et al. (1965) and Nash (I965) at 6oo and I415 MHz, by Kraus et al. (1966) at I4I5 MHz, by Williams, P. J. S., et al. (I 966) of I o67 sources at 38 MHz and by Kenderdine et al. (I 966) with the aperture synthesis telescope at Cambridge. The latter is the 5C·I survey at 408 MHz which lists Io6 sources in an area of about 12 square degrees, the weakest having flux densities S ~ 25 x lo- 29 w m- 2 Hz-1 and positional accuracies ~ 5" arc. In order to identify sources (Minkowski 1964) with galaxies fainter than I6m-17m better positional accuracies are required than are, in general, provided by the large-scale surveys. Special observations have therefore been made at the Owens Valley Radio Observatory (Fomalont et al. I964, Wyndham and Read 1965), at Pulkovo (Bystrova et al. 1964, Gol'nev and Parijskij 1965, Gol'nev et al. I965), at the Mullard Radio Astronomy Observatory (Clarke, M. E., I964, Wills and Parker 1966) and at Parkes (Shimmins et al. 1966b). These have reduced the errors to values typically 10"-15". For smaller numbers of sources positions have been determined to within a few seconds of arc by the method of lunar occultation (references later) and by interferometric techniques such as those at the Royal Radar Establishment, Malvern (Adgie I964, Adgie and Gent I966), at the N.R.A.O., Green Bank (Wade et al. 1965, Clark, B. G. and Hogg 1966) and at Cambridge (Parker et al. 1966). These measurements rely upon calibration of the equipment by means of accurately determined optical positions of sources (e.g. Griffin I963, Veron 1966a).

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Identification work following from these and other surveys has been described by Shobbrook (1963}, Hazard et al. (1964) Ryle and Sandage (1964), de Vaucouleurs (I965), Longair (x965}, Shakeshaft and Longair (I965), Shobbrook and Hunstead (I966) and Wyndham (I965, I966); the latter paper gives finding-charts and descriptions of objects in the neighbourhood of most of the sources in the revised 3C survey. Many identifications have been suggested from study of the Parkes catalogues by Bolton et al. (I 96 sa, I 96 sb ), Ekers and Bolton (I 96 5}, Bolton and Ekers (I966a, I966b, I966c, I966d}, Bolton and Kinman (I966), Bolton et al. (I966), Clarke, M. E. et al. (I966), Westerlund and Smith {I966), both with galaxies and also blue stellar objects. Comparison of lists of such objects with the 4C catalogue has also revealed significant coincidences (Aizu I966, Scheuer and Wills I966, Wills I966a, Caswell and Wills I967}, although for the great majority of them the radio emission is either extremely weak or undetectable (Dickel and McVittie 1965, Braccesi et al. I966a, I966b, Kellermann and Pauliny-Toth I966a, Kinman I966, Shapiro and Weinreb I966). Many of the identifications recently proposed remain to be confirmed, or otherwise, by improved radio positions and optical studies; this work is described in the report to Commission 28.

3· Spectra: flux density variations Because of their uniformity the spectral results by Conway et al. (I963) (see also Long et al. I963, Conway I96¥, Conway and Moran I964) have been widely used, although further measurements (Long and Shuter I963, Razin and Fedorov I963, Kellermann I96¥, 1964b, Zaharov et al. 1964, Boischot et al. I965, Clarke, M. E., I965, Conway et al. I965, Vetuhnovskaja and Kuz'min I965, Artjuh et al. 1966) are now available. Kellermann (I964c) has reviewed some of these new data and their interpretation. Howard et al. (I965) have also derived a uniform flux density system based on many earlier surveys but present studies (e.g. Long et al. I966) make use of the more reliable surveys recently completed (see section (z)). In virtually all of these papers, the flux densities quoted have been measured by comparison with those of intense sources. To calibrate them, absolute flux density measurements (Findlay I966) are required. These are not easy and for low frequencies the errors are still 1o-2o%. At high frequencies, however, the use of horn antennas (Lastochkin et al. I963a, I963b, Findlay et al. I965, Medd and Ramana 1965a, 196sb, Allen and Barrett 1966, Wilson and Penzias I966) has enabled the errors to be reduced to a few percent only. The range of frequencies over which flux densities have been measured has been extended; at low frequencies ( < 38 MHz) by the group at Kharkov (Bazeljan et al. 1964, Bazeljan et al. 1965a, 1965b, Braude 1966a), by Erickson and Cronyn (1965) at 26 MHz, Andrew (I967) at 13"1 MHz and by Guidice (1966). At high frequencies(> 3 GHz) observations have been made by Broten et al. 1965, Dent and Haddock (x965a, 1966), Gol'nev and Parijskij (1965), Williams, D. R. W. et al. (1965), Kellermann (1966a), Kostenko and Matveenko (1966), Maxwell and Rinehart (1966) and Yokoi et al. (1966). From these and other measurements it has become clear (e.g. Howard et al. 1964) that the spectra of a number of sources cannot be represented by the usual power law. In the microwave range, for example, the fluxes of 3C 84 (NGC 1275) and 3C 279 increase with increasing frequency (Dent and Haddock, 1965b). This phenomenon is associated with time variations of flux (see later) and small angular size (Barber et al. I966). At low frequencies it is found that some sources exhibit a relative reduction of flux (Williams, P. J. S. 1963) which is correlated with high brightness temperatures. This result has been interpreted in terms of synchroton self-absorption (Slys 1963) though there are other possibilities (Gajlitis and Cytovic 1963, Braude 1965a, Scheuer I965a, Hornby and Williams 1966). In other cases there is a relative increase at low frequencies which can be attributed BB2

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to components in the source with different spectral indices. Two examples are 3C 273 (Bailey et al. 1964, Conway et al. 1964, Solomickij et al. 1965a, Hazard et al. 1966a, von Hoerner 1966) and 3C 84 (Baars et al. 1965, Roger et al. 1965, Slepcova et al. 1965, Braude 1966b). Solomickij et al. (1964a, 1964b, 1965b) have found some other sources with apparently peculiar spectra but confirmation of this work is required. The spectra of some of the stronger sources have been studied in detail (Braude 1963, 1965b, Hrulev 1963, Baars et al. 1964, Lastockin 1964, Slys 1964, Stankevic 1964, Bazeljan 2t al. 1965c, 1966, Braude et al. 1966, Clark, T. A., 1966). A particularly interesting one is 1934-63, the radio spectrum of which is broadly peaked near qoo MHz and falls off rapidly above and below this frequency (Bolton et al. 1963, Kellermann 1966b). Sklovskij (1965a, 1965b) points out that there may be a detectable secular variation of its spectrum. This has not yet been found but the reality of irregular flux variations in certain other sources is now well established (after searches by Mayer et al. 1965), following the work of Dent (1965) on the quasi-stellar objects 3C 273, 279 and 345· It appears (Maltby and Moffet 1965a, Bartlett 1966, Kellermann and Pauliny-Toth 1966b, Moffet 1966a, Pauliny-Toth and Kellermann 1966, Yang and Dickel 1966) that the magnitude of the variations in these sources tends to increase with frequency above about 1 GHz; at centimetric and millimetric wavelengths there can be very rapid changes (Epstein 1965a, 1965b, Low 1965, Epstein et al. 1966). Another variable source (Dent 1966) is 3C 84, particularly significant because of its association with the Seyfert galaxy NGC 1275 rather than a quasi-stellar object. The first QSS reported as variable was CTA-102, (Solomickij 1965a, 1965b) from observations at 920 MHz. His later results (1966a) indicate a very regular fluctuation of intensity of a circularly-polarized component with a period 102 days. No other observers (Boischot 1965, Caswell and Wills 1965, Maltby and Moffet 1965b, Bologna et al. 1966, Nicholson, G. D. 1966) have detected any variation, though none has used precisely the same frequency or polarization. The evolutionary changes to be expected in source spectra are the subject of papers by Gajlitis and Cytovic 1964, Ohtani and Kogure (1964), Lequeux (1965), Souffrin and Chesnay (1965), de Ia Beaujardiere (1966) and Kellermann (1966c, 1966d). Studies of the radio spectra of 'normal' galaxies have been made by Hazard (1963), Kuril'cik (1964, 1965a, 1966a), Kenderdine and Baldwin (1965) and Kuril'Cik and Sycko (1965). 4· Brightness distribution Work on the structure of extragalactic sources has been reviewed by Moffet (1964a, 1966b), Hazard (1965) and Palmer (1965). Information on the brightness distribution in relatively extended sources can be obtained directly by means of antennas with narrow beams (Boischot et al. 1963, Little, A. G. 1963, Balklav 1964, Ko 1964, Labrum et al. 1964, Little, A. G. et al. 1964, Milne and Scheuer 1964, Parijskij and Prozorov 1964, Parijskij and Timofeeva 1964, Boischot and Kazes 1965, Broten et al. 1965, Scheuer 1965b, Thompson and Krishnan 1965, Little, A. G. and Bracewell 1966), but for higher resolution it is necessary to employ interferometric techniques or the method of lunar occultation (for zodiacal sources, Nicholson, W. 1965). A discussion of errors in measuring diameters has been given by von Hoerner (1965). The principal developments in interferometry have been the use of extended base-lines (Adgie et al. 1965, Anderson et al. 1965, Barber et al. 1966, Palmer 1966), revealing that some sources, particularly QSS, have structure subtending o'!r arc or less; and the production of a pencil-beam as small as 23" by means of 'aperture synthesis' (Ryle et al. 1965a, 1965b, Macdonald et al. 1966, Shakeshaft 1966), which has shown, inter alia, that the QSS 3C 47 has a double structure indistinguishable from that characteristic of most radio galaxies, and that some radio galaxies, e.g. 3C 465, have multiple components. Other interferometric work included that by Maltby

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et al. (1963) who discuss 24 identified sources in detail, by Moffet (1964b, 1964c), Tanaka et al. (1965), Zisk (1965), Clark, B. G. and Hogg (1966), Hogg (1966) and Wade (1966) who has found fine structure in each of the two radio components of Cyg A. The technique for analysing observations of a lunar occultation devised by Scheuer (1963) and developed by von Hoerner (1964a) has been applied to observations of 3C 273 by Bailey et al. (1964), Conway et al. (1964), Hughes (1965), Scheuer (1965a, 1965c), Hazard et al. (1966b) and von Hoerner (1966). Occultation observations of other sources include those of CTA 21 (Clarke, R. W. and Batchelor 1965, Taylor 1966), 3C 444 (de Jong 1966a, Taylor I966), MSH 19-27 (Brown 1966a), MSH 21-23 (Brown 1966b), 0938 + 18 and 1101 + II (Cohen and Kundu 1966), NGC 6523 (Larionov and Solomickij 1966, Solomickij 1966b), 3C I7 and 3C 132 (Taylor 1966). The prediction of occultations of radio sources for I7 radio observatories has been continued by the Nautical Almanac Office of the Royal Greenwich Observatory; details are given in the Explanatory Supplement. Information on small-scale structure ( < 1" arc) in sources can come from two other types of observation: (a) that of interplanetary scintillation due to the solar wind (Hewish et al. I964, Cohen 1965, Hogg and Menon 1966, Sinigaglia I966, Vitkevic et al. 1966). The manner in which scintillations vary with the angular distance between a source and the Sun is dependent upon the angular size and structure of the source (Cohen et al. 1966, Little, L. T. and Hewish I966); (b) low-frequency spectral cut-offs. If it is assumed that such a cut-off is due to synchroton self-absorption then there is a relationship between the brightness temperature, red-shift, magnetic field and cut-off frequency for the source (e.g. Hornby and Williams 1966). Knowledge of angular sizes can then put upper limits on the field strengths in sources (Williams, P. J. S., I966a) or, alternatively, assumptions about field strengths give upper limits to angular sizes. Williams, P. J. S. (1966b) has shown in this way that the ratio of separation to component sizes in the double source 3C 343/343'1 (previously studied by Moffet I965) is at least 2000:1. Gardner and Bolton (1965) have described another widelyspaced double source MSH 13-33. The dependence of source structure upon wavelength has been considered by Moffet and Palmer (1965) and by Jennison (1965).

5. Polarization The whole subject of polarization, for the galactic continuum radiation as well as for sources, has been reviewed recently by Gardner and Whiteoak (1966). Further observations of the linearly polarized radiation from sources have been made by Seielstad and Wilson (1963), Seielstad et al. (1963), Conway (1964b), Haddock and Hobbs (1964), Hollinger et al. (1964), Mayer (1964), Mayer et al. (1964), Morris and Berge (1964), Morris et al. (1964a), Radhakrishnan (1964), Roberts (1964), Rose (1964), Bologna et al. (1965), Gol'nev and Soboleva (1965), Boland et al. (1966), Gardner and Davies (1966) and Maltby and Seielstad (1966). These are nearly all measurements at various centimetric wavelengths of the percentage polarization and position angle of the electric vector for the integrated radiation from sources. It will clearly be vital to a full understanding of sources to know the distribution of polarization across them as a function of wavelength (as already determined for Centaurus A by the group at Parkes, e.g. Cooper et al. 1965). Examples of such measurements are those for Cygnus A with the fan-beam of the Pulkovo antenna (Soboleva and Timofeeva 1963, Soboleva 1966) for Pictor A (Broten et al. 1965), for Fornax A (Gardner and Price 1967), and for the source MSH 13-33 (IC 4296) (Gardner and Davies 1964) in which the intrinsic position angle of the electric vector from each of the three widely separated components is closely parallel to the axis of the source. Interferometric studies are, however, necessary in most cases in order to obtain higher resolution. These have so far been carried

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out only at the Owens Valley Radio Observatory (Morris et al. 1964-h, 1964£, Seielstad 1966) and at Parkes (referred to by Gardner and Whiteoak 1966). It is now clear that nearly all of the Faraday rotation observed for sources occurs in the Galaxy and can give information on magnetic field structure therein (Ginzburg and Pisareva 1963; see Section (C) for other references), but the decrease of polarization with increasing wavelength must be largely due to Faraday rotation occurring within the source; this has been considered by Pacholczyk (1963), Burn and Sciama (1964), Morris et al. (196 1oo MeV. Low Energy Solar X-rays, 8-14A. Cosmic and Solar Charged Particles, Gamma Rays.

Ames Research Center. Peterson, Univ. of California. Kraushaar, Clark, Garmire, Mass. Inst. of Technology. Teske, Univ. of Michigan. Kaplon, Deney, Denrik, Univ. of Rochester.

OSO-F Pointed section

Location Regions on Sun of Soft X-rays 3-18A. XUV Spectroheliograph, 284-1216A. Solar Spectroscopic Monitoring 1-4ooA.

Boyd, Willmore, University College, London; Pounds, University of Leicester. Purcell, Detwiler, Tousey, Naval Research Laboratory. Neupert, White, Goddard Space Flight Center.

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Wheel section Profile Solar and Geocoronal Lyman-oc.

Solar X-ray Monitoring o·s-6oA. Low Energy Solar and Cosmic Gamma Rays. Polarization Zodiacal Light. Solar XUV Monitoring, z8o-roJoA. Pointed section

Blamont, Centre National Recherche Scientifique. Chubb, Kreplin, Friedman, Naval Research Laboratory. Frost, Horstman, Roth, Goddard Space Flight Center. Ney, Univ. of Minnesota. Rense, Parker, Univ. of Colorado.

OSO-G

Offset Pointing Spectrometer-Spectroheliometer, JOo-rJooA. Location and Spectra Solar X-rays r-6oA. Wheel section Solar XUV Monitoring in Lines of He, 0 and N. Solar X-ray Line Monitoring, r6-4oA.

Brightness, Polarization Zodiacal Light. Solar X-rays and Gamma-rays, 2-zoo KeV. High Energy Neutrons zo-130 MeV.

Goldberg, Reeves, Parkinson, Huber, Harvard College Observatory. Kreplin, Chubb, Meekins, Friedman, Naval Research Laboratory. Boyd, Woodgate, University College London. Argo, Bergy, Evans, Henke, Los Alamos Scientific Laboratory. Carroll, Aller, Rutgers University. Brini, University of Bologna. Leavitt, University of New Mexico.

2.2 ESRO projects Dr B. Bolin has communicated an account of ESRO spacecraft and experiments, to be launched during the next few years. Those concerned with solar astronomy are as follows: ESRO 1: polar orbit of 90° inclination; apogee 1500 km; perigee 275 km; total weight 78 kg; scheduled for launching September-November 1967. Experiments include the measurement of auroral particles and solar protons in five experiments by three different groups, namely, (r) Kiruna Geophysical Observatory, Dr. Hultqvist; (2) Science Research Council, Slough, Dr Dalziel; (3) Ionosphere Laboratory, Lyngby. Mr Peterson is coordinator of all five experiments. ESRO II: near polar orbit of 98° inclination; spin stabilized; apogee 1100 km; perigee 350 km; scientific payload 20 kg; scheduled for launching, March 1967; intended for studies in the field of cosmic rays and solar astronomy, of cosmic rays in interplanetary space, modulation mechanism of primary cosmic radiation; electron component, solar corpuscles and electromagnetic radiation and trapped protons of the inner Van Allen belt. Solar experiments include (r) Study of the variations of X-rays below 2oA from the quiet Sun, with five proportional counters, by Boyd, University College, London and Stewardson, University of Leicester; (2) Study of the variations of X-rays in the region 44-7oA, with two proportional counters, by de Jager, Utrecht Observatory; (3) Measurement of flux and energy spectrum of solar protons (35 MeV-1 GeV) with telescope comprising solid state detectors, by Labeyrie, Centre d'Etudes Nucleaires de Saclay. TD-1: the first ESRO medium size stabilized (Sun pointing) satellite; near polar circular orbit of 98° inclination; altitude 56o km; scientific payload So kg; scheduled for launching in early 1970. Two solar experiments are (r) Monitoring of solar X-rays, 40-300 KeV with scintillation counter, by de Jager, Utrecht Observatory and (2) X-ray spectrometry 3-30 KeV, with proportional counter, by Labeyrie, Saclay. A second satellite in the series, TD-2, is a solar maximum satellite, to be launched

OBSERVATIONS AU-DEHORS DE L'ATMOSPHERE TERRESTRE 983 TD-1:

by an improved Thor Delta during the latter part of 1969 into an orbit of as yet undetermined inclination, with apogee 1200 km and perigee 350 km. The satellite will carry a number of solar experiments: ( r) High resolution spectrometry of solar X-ray emission with a crystal spectrometer, by Stewardson, University of Leicester; (2) Monitoring of the profile of the solar Lyman-o.: line, with a hydrogen or deuterium cell and photomultipliers, by Blamont, C.N .R.S.; (3) Monitoring of solar particles (13-160 MeV protons) with a solid-state detector telescope, by de Jager, Utrecht Observatory; (4) Monitoring of solar particles (o·6-28 MeV protons) with a scintillator employing solid state detectors, by Liist, Max Planck Institute, Munich; (5) Extreme ultraviolet solar spectrography, with a spectraheliograph, by Boyd, University College, London.

HEOS-A: inclination of orbit 33°; apogee 240 ooo km; perigee 200 km; spin stabilized, scheduled for launching in July 1968, will carry eight experiments for the measurement of particles and fields in the interplanetary medium. 2.3 Other proposed experiments 2.3.1 Utrecht Observatory. According to C. de Jager, the new Space Research Laboratory of Utrecht Observatory participated or is participating in the following projects: (r) Rocket observations of soft solar X-rays (44-6oA), in the French national program, and with ESRO (launchings in 1964, 1965, 1966). Precise measurements of the soft X-ray flux were obtained during the years of solar minimum activity. (2) A satellite experiment in the same wavelength band has been prepared for launching in the ESRO II satellite in April 1967. (3) Balloon launchings for the detection of hard solar X-ray bursts between 20 and 6oo KeV take place regularly. (4) An extreme ultraviolet and X-ray solar heliograph will be flown early in 1967 in a sun-pointing NASA rocket at White Sands. The heliograph is based on the Fresnel-type zone plate principle and is designed to obtain solar images in Si IX 5IA; Fe VIII-X r8oA; He II 304A and He I 584A. (5) A high-resolution solar spectrophotometer for the region 44-64A is in preparation for flight in an ESRO sun-pointing rocket in November 1966. 2.3.2 University of Tokyo. Dr Z. Suemoto reports that an institute of space and aeronautical science was established in 1964 in the University of Tokyo to promote the further development of space and aeronautical science in Japan. It is expected that the facilities of the new institute will be utilized by scientists in relevant fields of research throughout Japan. The new institute has a launching site at Uchinoura Kagoshima in Kyushu, which began operation late in 1963. Typical sounding rockets now in use in Japan are the K-9M, which carries a payload of 6o kg to a maximum height of 350 km and the L-3 with a payload of uo kg and a maximum height of uoo km. The so-called MU rockets, which are capable of launching satellites, are under development and satellite projects are being seriously considered. To date only some preliminary experiments on the height variation of the solar Lyman-o.: flux have been performed (II).

2.3.3 Stockholm Observatory. DrY. Ohman reports that he is designing a spectrograph for recording the spectrum of various parts of the solar surface from an unstabilized rocket. The instrument uses a large number of small lenses placed on a spherical surface. The focus of all these lenses is situated in the center of curvature. Here a very small (about o·5 mm) reflecting sphere is used, functioning as a slit for a spectrograph. By using a continuously moving film, tracings are obtained when the various lenses happen to project the solar image on the small sphere. The instrument is mainly intended for the study of the Mg II lines at 28ooA in solar flares. Dr K. Fredga is developing an improved instrument for recording solar images in the Mg n line at 2802·7A for flight in the near future. J. 0. Stenflo has started the design of a spectrograph, which he hopes to use in space research for studying solar magnetic fields in small structure elements of the solar surface. HH2

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2.3.4 Meudon Observatory. Dr A. Dollfus reports as follows on his plans to photograph the solar corona from high altitude balloons: 'En ce qui conceme plus particulierement les activites de moo laboratoire, je prepare une serie de vols en ballons, depuis le Centre de Lancement de Aire-sur-Adour (Landes) pour Ia photographie des grands jets de Ia couronne solaire. L'instrument est un petit coronographe precede d'une poutrelle portant un cache a 4 metres en avant de l'objectif et destine a porter ombre sur celui-ci, afin de reduire la lumiere diffusee a UO facteur Io-8 ; le contour de Ce cache est forme de 36o dents de o·4s mm de profondeur afin de diminuer la brillance de la lumiere refractee par ce contour. La nacelle stabilisee et le dispositif de pointage automatique ont ete ooo m 3 en construits par la Societe Frans;aise 'Compagnie des Compteurs'. Le halloo de feuille plastique de polyethylene de 4op. d'epaisseur atteint !'altitude de 30 ooo metres. Le premier vol est prevu pour le debut de l'annee 1967.' 2-3·S University College, London. At the University College, London, R. L. F. Boyd and his collaborators are planning to make accurate absolute measurements of the flux of solar Lyman IX at intervals in the solar cycle. An experiment to study the center to limb variation in Lyman IX was to be flown during the annular solar eclipse of IS May 1966. The University College group in collaboration with Leicester are preparing satellite-borne instruments containing arrays of proportional counters to study the wavelength bands 1-2oA and 44-7oA on board OSO-D and the band 1-2oA on ESRO II. 2.3.6 Imperial College. Dr R. Speer, Imperial College, U.K., has called attention to a unique opportunity to observe XUV radiation at the solar limb with very high spatial resolution during the solar eclipse of March 1970, which passes over the Wallops Island Launching Facility of NASA. He comments that: 'The azimuth, geographic coordinates and speed of the umbra permit trailing stabilised rocket trajectories capable of yielding chromospheric limb scan rates in the range o·2 to o·4 seconds of arc per second of time. It is proposed that, at minimum, three stabilised Aerobee 3SO rockets be launched, carrying modified STRAP control systems. These launchings will occur at equal intervals during a three-minute period centred around maximum eclipse. It is suggested at this stage that a carefully chosen selection of emissions be made from ions of HI, He I, He II and the Li-like iso-electronic series, together with a portion of the continuum at 14ooA-16ooA associated with the chromosphericfphotospheric temperature reversal. A measurement of the Balmer IX line of helium II at 164oA, if combined with observations of the other helium II lines outside of eclipse would provide the first direct measurement of helium abundance in the chromosphere.' 2.3.7 Geneva Observatory. Professor M. Golay is preparing to launch a rocket equipped to carry out photoelectric photometry of the Sun in several regions of the UV spectrum.

so

3· Solar Ultraviolet, X-rays and Gamma Rays Most observations of the Sun's XUV radiation during the past two to three years have been made in the short wavelength region below sooA. Important gains have been made in spectroscopic resolution, in the mapping of the ultraviolet solar spectrum above the limb, in the spatial resolution of ultraviolet and X-ray images and in X-ray spectroscopy. Most of the results have been obtained by the use of sounding rockets, but small satellites have played an important role in the monitoring of X-rays. 3.1 Solar Spectra The high resolution echelle spectrograph first flown in 1961 by the Naval Research Laboratory was reflown on 19 November 1964 and the solar spectrum extended from 22ooA to 210oA (3). No measurements from either of these spectra have been reported but there are plans to publish a list of lines with identifications and an atlas showing intensity profiles. With the aid of a

OBSERVATIONS AU-DEHORS DE L'ATMOSPHERE TERRESTRE 985 new tri-axial stabilization system developed for the Skylark rocket, the Culham Laboratory flew a spectrograph on 9 April I965 with the entrance slit placed about ten arc sec outside the solar limb (12, I3)· Photographs of the ultraviolet spectrum between 95oA and 295oA show about 300 emission lines, including intersystem transitions inC III, N IV, 0 v and new forbidden transitions in Fe XI and Fe XII (I4). New measurements of absolute fluxes in the solar XUV spectrum were made by photoelectric scanning from 3IoA to 55A (IS, I6, I7) and by photography in the spectral intervals 25oA to 37oA and 33A to 7oA (IS). Absolute fluxes in the spectral region from I75oA to I A have been tabulated for relatively quiet solar conditions (I9)· The first recordings of solar X-ray spectra with a Bragg crystal spectrometer were carried out in I963 to a short-wavelength limit of I3A (2o). In the U.S.S.R., photographs and spectra of the Sun in short-wave ultraviolet and X-radiation were obtained with apparatus on board two geophysical rockets, which attained heights of nearly 500 km on 20 September and I October I965 (2I). During the I October flight, photographs and spectra of the Sun were obtained for the first time during the beginning stages of an X-ray flare. During the flare, the intensity of the Fe XVII line at ,\ = I5·oA increased by two orders of magnitude as compared with its intensity in the absence of solar flares. A review of the variability of the solar X-ray spectrum below I5A has been published (22), based on U.K. observations with sounding rockets and the Ariel satellite during the period I959-63. H. Friedman reports the observation by NRL, on 4 October I966, of solar X-ray emission lines identified with Na XI, Mg XI, Al XII, Si XIII and Si XIV in the spectral region 6A to 8A. 3.2 Ultraviolet images The first monochromatic photographs of the Sun in the Mg II line at 2802·7 A were obtained with a Cassegrain-Maksutov telescope and a Sole-type birefringent filter on board an Aerobee rocket on I2 April and 2 December I965 (23). A photoionization detector behind a pinhole placed at the focus of a Cassegrain telescope of two seconds of arc resolution recorded the fine structure of the Sun in Lyman oc during an Aerobee flight on 20 October I965 (24). Rapid progress is being made in the improvement of techniques for solar imaging at extreme ultraviolet and soft X-ray wavelengths. The Culham Laboratory in the U.K. has developed a compact extreme ultraviolet spectroheliograph in which a pinhole camera is combined with a plane diffraction grating used at grazing incidence (I3). The instrument was flown in a stabilized Skylark rocket on 9 April I965 and recorded monochromatic images at 304A (He II), I7I A (Fe IX), and strongly limb brightened emission in the wavelength band between 6oA and I 5o A. High quality monochromatic images have recently been obtained by the Naval Research Laboratory with a normal incidence concave grating spectroheliograph in such lines as Fe xv 284A, Fe XVI 335 A 36I A, He II 304A, and many others, the most recent flight having taken place on 28 April I966 (25). The emission in the strongest lines was observed to extend five arc minutes or more beyond the limb. Accordingly, a photographic extreme ultraviolet heliograph, consisting of an off-axis paraboloidal mirror, with filters transmitting a band from I7I A to about 4ooA, was flown on 27 July 1966 and revealed emission above active regions extending at least to thirty arc minutes above the limb (26). 3·3 X-ray images The distribution of X-ray emitting sources over the solar disk has been studied in four different ways: (1) from the widths of X-ray emission lines observed with a Bragg crystal spectrometer (2o), (2) by means of slit scans of the solar disk in broad X-ray wavelength bands (2o), (3) by pinhole photography (27-30) and (4) by photography with a grazing incidence imaging telescope (3I, 32). The newest observations (32) suggest that X-ray images may soon be recorded with spatial resolution of one second of arc or better.

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3·4 Monitoring of Solar X-ray Emission The Solrad satellites of the Naval Research Laboratory have been monitoring the total flux from the Sun in the three wavelength ranges 2-SA, 8-2oA and 44-6oA. Results have been reported from three such satellites, I963-2I-C (33) I964-oi-D (34, 35, 36), and I965I6-D (37). Observations made by the Injun I satellite during the second half of I96I at wavelengths shorter than I4A have also been reported (38). The first orbiting solar observatory monitored solar X-rays at 2-8A and at 20-IOO keV (39). The 2-8A X-ray flux was found to be highly variable, comprising a slowly varying component that correlated well with plage activity and additional variations in time periods ranging from one second to several hours (40). A number of high energy bursts accompanying solar flares were observed in the 2Q-IOO keV range (41). Observations of solar X-rays in wavelength bands peaked at about 2A and about 4A were made from a Vela satellite during the period I8 October to I November I963 (42). An important set of measurements of the spectral energy distribution of solar flare X-rays was carried out with a low-resolution proportional counter spectrometer for the region 4-I4A on board the U.K. satellite Ariel I between 26 April and I November I962 (43, 44). Soft X-radiation from the Sun in two spectral intervals, 2-10A and 8-I8A, were carred out during flights of the cosmic stations Electron II and Electron IV in the U.S.S.R. (45). Measurements with the Electron II station extended from 30 January to I6 March I964. The X-ray flux was well correlated with the area of active spots, with the flux of radio radiation at I0·7 em wavelength and with the flux of radio radiation from discrete sources at 6·6 em wavelength. Many X-ray flares were observed both with and without the accompaniment of chromospheric flares. Two cases were observed in which X-ray flares were associated with an increase in the flux of heavy nuclei with Z > I 5 (46). No indication of a statistically significant flux of solar gamma rays in the energy range up to IO MeV could be detected from balloon measurements of the quiet Sun (47, 48). 4· Visible and Infrared Radiatian Observations of visible and infrared solar radiation and of the zodiacal light have been carried out from aircraft, balloons, rockets and satellites. The solar spectrum from I40-IOOO cm-1 was recorded with a Michelson interference spectrometer flown in a balloon on 10 August 1965 (49). Jet aircraft were employed at the eclipse of 20 July 19i}3 for the observation both of the coronal spectrum A37oo-..\4900 (5o) and of the solar corona at large distances from the Sun (51). Coordinated observations of the corona from the solar limb to the zodiacal light were also carried out during the same eclipse from the ground, from a balloon at 100 ooo feet (30 km) altitude and from a jet aircraft (52). White light coronagraphs were also flown in stratospheric balloons on 5 March 1964 (53), 3 June I965 and I July 1965 (54), and from Aerobee rockets on 28 June 1963 (55) and in 1966 (56). The balloon observations in 1965 were closely coordinated with ground observations including those during the total solar eclipse of 30 May I965. During this eclipse, profiles of the emission line ..\5303 were obtained with a Fabry-Perot interferometer (57) from an aircraft instrumented by the Los Alamos Scientific Laboratory. On 14 June I966, the outer solar corona was photographed with the Surveyor I television camera on the surface of the Moon after the solar disk had set behind the western horizon (58). The corona was traced out to an estimated 3 to 4 solar radii from the center of the disk and a very prominent coronal streamer, corroborated by ground-based measurements, was also apparent. A Japanese K-9M rocket was flown on 26 July 1965 with equipment to measure the zodiacal light photoelectrically at three wavelengths, 43ooA, 53ooA and 6oooA (59). The measured region was approximately 40° to 15° from the Sun, which covers the well-known gap between the observation of the zodiacal light and of the corona. The zodiacal light was also observed at 5oooA and 42ooA from a balloon flown by H. Tanabe and M. Huruhata of the Tokyo

OBSERVATIONS AU-DEHORS DE L'ATMOSPHERE TERRESTRE 987 Observatory at an altitude of Z5 km on Z7 September 1966. Photoelectric measurements of the zodiacal light were obtained from apparatus in the wheel section of OSO II, beginning in February 1965 (6o).

5· Laboratory and Theoretical Spectra, Identifications The very large number of unidentified lines in the ultraviolet solar spectrum continues to challenge astrophysicists and laboratory spectroscopists. It has been suggested that many of the unidentified solar emission lines below Al5oo may be attributed to the attachment of quarks to ions of C, Nand 0 (6x, 62). Considerable progress has been made in the identification of lines in the region z5-25oA (63--70). All of the strong lines in the solar spectrum between 167 A and zzoA have now been classified and identified by means of a number of ingenious laboratory techniques, (71--74). At the Culham Laboratory the wave numbers of lines are traced back along an isoelectronic sequence to well-classified ions. Another way of differentiating between atomic spectra and high stages of ionization is to photograph the spectra separately with two sources of considerably different excitation (75--78). Nearly all of the strong lines from 167A to 188A in the solar spectrum arise from the ions Fe vm-Fe XII. Intense lines between 188A and zzoA are shown to be due to unclassified lines of Fe xn-Fe XIV. The majority of the emission lines in the solar spectrum in the range 6oA-17oA are due to Fe and Ni, mostly the former. Other solar emission lines in the region from 310A to 55A have been identified on the basis of term differences in the tables of atomic energy levels (79). The resonance lines of Fe XIV have not been observed in the laboratory and therefore their solar identification presents a special problem. One aid to identification is the requirement that two lines having a common upper state and terminating in the ground term must be separated by an amount corresponding to the wave number of the forbidden line 5303 A (3). The intensity variations of extreme ultraviolet lines observed from the OS0-1 satellite also provide added clues to the identifications (So--82). It has been shown that the very low electron density in the solar corona relative to laboratory sources causes anomalies in the relative intensities within certain multiplets, notably the P-D multiplet of Fe XIV at 21o-zzoA (73). Shock-excited absorption spectra of solar-abundant atoms and molecules are being produced in the Shock Tube Laboratory of the Harvard College Observatory to assist in the identification of the solar spectrum between 3000 A and 1500 A. The identification of the fourth positive system of CO in the solar spectrum by this technique (83) has now been confirmed in detail at the Naval Research Laboratory (84).

6. Problems of Interpretation 6.1 Opacity near 16ooA The recognition that bound-free absorption by Si I and Mg I (85) and band absorption by the fourth positive system of CO (83) are the major sources of opacity in the spectral region 155oA-18ooA has provided a fresh basis for the interpretation of solar radiation from the region of the temperature minimum at the interface photosphere-chromosphere. New discussion of possible models of the region of the temperature minimum has been carried out in conjunction with careful laboratory measurements of the relevant cross-sections (86). Improved measurements of energy distribution and limb darkening are required for a definitive model. Various methods of correcting for instrumental broadening of the solar ultraviolet limb darkening profile have been investigated (S,). Theoretical profiles for the solar autoionizing lines of AI I at A. 1930 show that at the limb the profiles are extremely sensitive to the choice of model and may possibly exhibit emission reversals (88). The profiles of Lyman a: scattered by free electrons in the solar corona have been calculated for a number of points above the solar limb (89).

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6.2 Emission line intensities A new method for computing the total intensities of emission lines formed out of thermodynamic equilibrium (90) has been applied to compute the intensities of the solar ultraviolet lines and continua of H, He 1 and He II (91, 92). Another investigation deals with the formation of the Lyman continuum in an isothermal atmosphere (93). Both electron temperature and density may be inferred from the observed total intensities of Lyman a: and f3 (94). Extreme ultraviolet line intensities inferred theoretically from radio emission measures are at least ten times stronger than those observed (95). The discrepancy can be eliminated by invoking an inhomogeneous model. The method of analysis originally developed by Pottasch for the derivation of chemical abundances in the solar corona from far ultraviolet line intensities has been rediscussed in two separate investigations in which the ratios Fe to Si (96) and Fe to H (97) are found to be approximately ten times greater than in the photosphere. Other investigators obtain relative abundances of heavy elements (98) and abundances relative to H (99) which are consistent with those found in the photosphere. The abundances of C, Mg, S and Al relative to Si also seem to be consistent with photospheric abundances according to line intensities observed in the spectral regions 4o-62A and 256-356A (xoo). 6.3 X-ray emission The interpretation of the X-ray emission from the quiet Sun and from flares has received a great deal of attention. Solar X-radiation has been classified as quasi-thermal (emitted from quiet Sun, active regions and flares) or nonthermal (emitted from solar flares only) with a further sub-division for flare associated bursts (101). Detailed calculations (102, 103) support the assumption of a thermal origin of X-ray radiation from the quiet Sun and from active regions. Above ISA, the main contribution to the spectrum is from lines of C, Nand 0. At wavelengths shorter than I 5 A, the chief contribution is from recombination of highly ionized species of the same and other elements (102, 104). In the absence of solar flares, the radiative flux consists of a quasi-constant component generated in the undisturbed region of the corona on which is superposed a slowly varying component generated in the hotter, denser, active regions of the corona. It can be shown that when the emission measure and the electron temperature of active regions in the corona are derived from radio spectroheliograms of the Sun at a wavelength of 10·7 em, the calculated and experimental values of the X-ray flux are in good agreement (IOJ, 105). A number of detailed theoretical investigations concerned with possible mechanisms for the origin of X-ray flares have been carried out in the U.S.S.R. Compton scattering of thermal photons by relativistic electrons has been examined (xo6xo8) as well as the thermal synchrotron radiation of accelerated electrons (109). The inverse Compton effect has been criticized on the grounds that any quantity of relativistic electrons producing a measureable amount of inverse Compton photons will always produce a greater flux of high energy Bremsstrahlung photons than has been observed (no). It has been suggested that electrons with energy in the range Io-30 keV, which are produced during solar flares, may ionize atoms through K-shell ionization and that the resulting X-rays would contribute to the total X-ray emission of flares (111). The expectations with respect to gamma-ray emission have been calculated for a simple model of a solar flare (112). The detection of such radiation from a flare seems feasible. 6.4 Ionization equilibrium The importance of dielectronic recombination as a major factor in the theory of ionization equilibrium of the solar corona is now firmly established (113). A convenient general formula has been provided for the calculation of the relevant rates which may surpass the corresponding radiative rates by I to 3 orders of magnitude (114). The collisional excitation of autoionizing levels and subsequent ionization may in individual cases increase the rate of ionization by about a factor of 2 (115).

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XUV heliograms, paper presented at AAS Special Meeting 26. Purcell,]. D., Tousey, R. on Solar Astronomy, Boulder, Colorado, 3-5 Oct. 1966. 1964, Solar 27. Zhitnik, I. A., Krutov, V. V., Malyaukin, L. P., Mandel'Shtam, S. L. images in the far ultraviolet part of the spectrum, Cosmic Res., 2, Sox, translated from Kosm. Issled., 2, 920, 1964. 1965, Soft X-ray image of the Sun, Nature, 205, 6S4. 28. Russell, P. C. 1965, Further soft X-ray images of the Sun, Nature, 208, 2S1. 29. Russell, P. C. 1966, Improved resolution X-ray photographs of the 30. Russell, P. C., Pounds, K. A. Sun, Nature, 209, 490. 1965, 31. Giacconi, R., Reidy, W. P., Zehnpfennig, T., Lindsay, J. C., Muney, W. S. Solar X-ray images obtained using grazing incidence optics, Astrophys. J., 142, 1274. X-ray photographs of the solar corona, paper pre32. Underwood, J. H., Muney, W. S. sented at AAS Special Meeting on Solar Astronomy, Boulder, Colorado, 3-5 Oct. 1966. 1964, Observations of solar X-ray emission in the band 44-6oA from 33· Thomas, L. U.S. Naval Research Laboratory satellite 1963-21-C, Nature, 203, 962. 1965, NRL solar radiation monitoring satellite: description of instru34· Kreplin, R. W. mentation and preliminary results, Space Res., 5, 951. 1965, Measurements of solar X-ray 35· Thomas, L., Venables, F. H., Williams, K. M. fluxes by the U.S. Naval Research Laboratory satellite 1964-ox-D, Planet. Space Sci., 13, So7. 1964, Some 36. Landini, M., Piattelli, M., Righini, G., Russo, D., Tagliaferri, G. L. preliminary results from the solar monitoring satellite NRL 1964 1 D obtained at the Arcetri station, Ann. Astrophys., 27, 765 (also in 1964, IAU Symposium No. 23, Liege). Monitoring of X-rays by Solrad-8 (1965-16-D), Report of Seventh 37· Friedman, H. COSPAR Space Science Symposium, Vienna, Austria 1966. 1965, Solar X-ray observa38. Van Allen, J. A., Frank, L.A., Maehlum, B., Acton, L. W. tions by Injun 1, J. geophys. Res., 70, 1639. 1965, Comments on X-rays emitted by the Sun, Ann. Astrophys., 28, 39· Lindsay, J. C. 586 (also in 1964, IAU Symposium No. 23, Liege). 1964, Space Res., 4, 771. 40. White, W. A. 1965, Comments on high energy X-ray bursts observed by OSO-x, Space 41. Frost, K. ]. Res., 5, 513. 1965, 42· Conner, ]. P., Evans, W. D., Montgomery, M. D., Singer, S., Stogsdill, E. E. Solar flare X-ray emission measurements, Space Res., 5, 546. Singer, S., Conner, J. P., Evans, W. D., Montgomery, M. D., Stogsdill, E. E. 1965, and Plasma observations at 105 km, Space Res., 5, 546. 1964, 43· Bowen, P. ]., Norman, K., Pounds, K. A., Sanford, P. W., Willmore, A. P. Measurements of the solar spectrum in the wavelength band 4 to 14A, Proc. R. Soc. London Ser. A, 281, 538. 1965, Recent solar X-ray studies in the United Kingdom, Ann. Astrophys., 44· Pounds, K. A. 28, 132 {also in 1964, IAU Symposium No. 23, Liege). 1965, Investigation of Cosmic Space, Nauka, Moscow. 45· Tindo, I. P. 46. Kumosova, L. V., Mandel'Shtam, S. L., Razorenov, L. A., Tindo, I. P., Fradkin, M. I. 1966, Kosm. Issled., 4, 170. 1966, A search for the quiet-time solar gamma 47· Frost, K. ]., Rothe, E. D., Peterson, L. E. rays from balloon altitudes, J. geophys. Res., 71, 4079. 1966, The upper 48. Peterson, L. E., Schwartz, D. A., Pelling, R. M., McKenzie, D. limit solar gamma-ray spectrum to 10 MeV, J. geophys. Res., 71, 5778. 1966. Decrement of the solar continuum in the far infra-red, Nature, 209, 1226. 49· Beer, R. 1964, An airborne observation of the coronal spectrum at go. Deutsch, A. ]., Righini, G. the eclipse of 20 July, 1963, Astrophys. J., 140, 313. 1966, Observations of the 1963 July 20 solar eclipse. I. 51. Blackwell, D. E., Petford, A. D. Spectroscopic separation of the F and K components of the solar corona at large distances from the Sun, Mon. Not. R. astr. Soc., 131, 383. 1964, Observations of the solar corona from the 52. Gillett, F. C., Stein, W. A., Ney, E. P. limb of the Sun to the zodiacal light, July 20, 1963, Astrophys. J., 140, 292.

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53· Newkirk, G., Jr., Bohlin, J. D. 1965, Coronascope II: Observation of the white light corona from a stratospheric balloon, Ann. Astrophys., 28, 234 (also in 1964, IAU Symposium No. 23, Liege). 54· Bohlin, J. D., Hansen, R. T., Newkirk, G. A. The three dimensional structure of a coronal streamer and the inner solar wind, paper presented at AAS Special Meeting on Solar Astronomy, Boulder, Colorado, 1-3 Oct. 1966. 55· Tousey, R. 1965, Observations of the white light corona by rocket, Ann. Astrophys., 28, 6oo (also in 1964, IAU Symposium No. 23, Liege). 56. Koomen, M. J., Purcell, J. D., Tousey, R. The white light corona from R = 4 to I I"S R. Paper presented at AAS Special Meeting on Solar Astronomy, Boulder, Colorado, 1-3 Oct. 1966. Coronal emission line profiles of A5303 obtained at the 30 May 57· Liebenberg, D. H. 1965 total solar eclipse, paper presented at 123rd meeting of the Amer. Astr. Soc., Los Angeles, 27-30 Dec. 1966. 58. Gunn, J. E., Norton, R. H. Surveyor I observations of the solar corona, paper presented at AAS Special Meeting on Solar Astronomy, Boulder, Colorado, 1-3 Oct. 1966. In preparation. 59· Tanabe, H., Huruhata, M. 1966, Observations of the sky, Earth, and airglow from OSOB, 6o. Ney, E. P., Huch, W. F. Astr. J., 71, 393 (also in AAS Meeting, Hampton, Virginia, March 1966). 61. Sinanoglu, 0., Skutnik, B., Tousey, R. 1966, Search for quarks in the far ultraviolet solar spectrum, Phys. Rev. Lett., 17, 785. 62. Bennett, W. R., Jr. 1966, Detection of quarks in the ultraviolet solar spectrum. Phys. Rev. Lett., 17, 1196. 1964, A method of differentiating between 63. Alexander, E., Feldman, U., Fraenkel, B. S. atomic spectra of high degrees of ionization, J. quantit. Spectrosc. radiat. Transfer, 4, sox, 1966, Unclassified Jp 6 3d-3p 5 3d 4S transition lines of 64. Feldman, U., Fraenkel, B. S. Fe VIII, Mn VII, and Cr VI, Astrophys. J., 145, 959· 1966, 65. Fawcett, B. C., Gabriel, A. H., Irons, F. E., Peacock, N.J., Saunders, P. A. H. Extreme ultra-violet spectra from laser-produced plasmas, Proc. Phys. Soc., 88, 1051. 1966, New inner-shell resonance lines in highly 66. Deutschman, W. A., House, L. L. ionized sulfur and chlorine, Astrophys. J., 144, 435· 1964, Comparison of solar and 67. House, L. L., Deutschman, W. A., Sawyer, G. A. laboratory iron spectra in the vacuum ultraviolet, Astrophys. J., 140, 814. 1964, Origin of 68. Elton, R. C., Kolb, A. C., Austin, W. E., Tousey, R., Widing, K. certain solar emission lines between 170 and 22oA, Astrophys. J., 140, 390. 69. House, L. L. 1964, The laboratory production of solar iron lines in the vacuum ultraviolet, Ann. Astrophys., 27, 763 (also in 1964, IAU Symposium No. 23, Liege). 1965, Labora70. Mandel'Shtam, S. L., Fedoseyev, S. P., Kononov, E. Ya., Lebedev, S. V. tory reproduction of the short-wavelength portion of the solar spectrum, Optics Spectrosc., 18, 522. 71. Gabriel, A. H., Fawcett, B. C., Jordan, C. 1965, Classification of iron lines in the spectrum of the Sun and Zeta in the range 167 A to 22oA, Nature, 206, 390. 72. Fawcett, B. C., Gabriel, A. H. 1965, New spectra of the iron transition elements of astrophysical interest, Astrophys. J., 141, 343· 73· Gabriel, A. H., Fawcett, B. C., Jordan, C. 1966, Classification of iron VIII to XII and XIV lines in the solar XUV spectrum and their isoelectronic sequences from argon to nickel, Proc. phys. Soc., 87, 825. 1966, Spectra from 3Pn - 3Pn-l 3d transitions of iron 74· Fawcett, B. C., Gabriel, A. H. period elements in Cl I and S I isoelectronic sequences, Proc. phys. Soc., 88, 262. 1965, Identifications of solar ultraviolet lines 75· Feldman, U., Fraenkel, B. S., Hoory, S. resulting from a study of the Ar I and K I isoelectronic sequences, Astrophys. J., 142, 719. 1965, 3P6 - 3P 5 3d transitions 76. Alexander, E., Feldman, U., Fraenkel, B. S., Hoory, S. of Fe IX and Ni XI in the solar spectrum, Nature, 206, 175. 77· Cowan, R. D., Peacock, N. J. 1965, Identification of some intense iron lines in the solar spectrum near 17oA, Astrophys. J., 142, 390.

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78. Gabriel, A. H., Fawcett, B. C. I965, Identification of the solar spectrum in the region 6o-I7oA, Nature, zo8, 8o8. I964, Identification of extreme ultraviolet solar emission lines, Astrophys. J., 79· Zirin, H. I400 I332. I965, Intensity variations in the solar extreme ultraviolet spectrum So. Neupert, W. M. observed by OSO-I, Ann. Astrophys., z8, 446 (also in I964, IAU Symposium No. 23, Liege). Sr. Neupert, W. M., Smith, E. V. P. I964, Possible identification of permitted Fe XIV lines in the extreme ultraviolet solar spectrum, Astr. J., 69, 554 (also in I964, paper presented at I I 6th meeting AAS, Flagstaff). Sz. Stockhausen, R. I965, The UV lines of Fe XIV in the solar corona, Astrophys. J., 141, 277· I965, Carbon monoxide in the ultra83. Goldberg, L., Parkinson, W. H., Reeves, E. M. violet solar spectrum, Astrophys. J., 141, I293· 84. Porter, J. R., Tilford, S. G., Widing, K. G. Carbon monoxide in the solar ultraviolet spectrum (in press). 85. Rich, J. C., Gingerich, 0. I966, Metallic continuous absorption coefficients in the solar ultraviolet, Astr. J., 71, I6I. 86. Rich, J. C. Silicon and carbon monoxide absorption in the solar ultraviolet spectrum, Ph.D. Thesis, Harvard University, Nov. I966. 87. Lacis, A. A., Matsushima, S. I965, Method of correction for instrumental broadening to determine the solar ultraviolet limb-darkening, Astr. J., 70, I42 (also in I964, paper presented at I I 7th meeting AAS, Montreal). 88. Withbroe, G. L. 1966, Theoretical profiles for the solar auto-ionization lines of AI I, Astrophys. J., 146, 294· 89. Hughes, C. J. 1965, Profiles of Lyman-alpha scattered by free electrons in the solar corona, Astrophys. J., I4Z, 321. 1965, Theoretical line intensities: I. Strong enission lines; II. Excitation 90. Athay, R. G. of chromospheric He II and hydrogen, Astrophys. J., I4Z, 724. 1965, Theoretical line intensities: III. Solar UV lines and continua of 91. Athay, R. G. H, He I, and He II and the chromospheric model, Astrophys. J., I4Z, 755· 9Z. Athay, R. G. 1966, Theoretical line intensities: IV. Source functions and equivalent widths, Astrophys. J., 144, II59· 93· Dietz, R. D., House, L. L. 1965, The formation of the Lyman continuum: isothermal atmosphere, Astrophys. J., 141, 1393. 94· Hearn, A. G. 1966, An interpretation of the total intensities of the Lyman a: and fJ lines of hydrogen emitted by the Sun, U.K. Atomic Energy Authority, Research Group, Culham. 1964, Spotty appearance of the solar disk as inferred from 95· Suemoto, Z., Moriyama, F. the comparison between EUV and radio intensities, Ann. Astrophys., z7, 77S (also in I964, IAU Symposium No. 23, Liege). 96. Jordan, C. 1966, The relative abundance of silicon, iron, and nickel in the solar corona, Mon. Not. R. astr. Soc., IJZ, 463. 97· Jordan, C. 1966, The abundance of iron in the solar corona, Mon. Not. R. astr. Soc., IJZ, SIS. 98. Athay, R. G. 1966, Theoretical line intensities: V. Solar UV emission lines of heavy elements, Astrophys. J., 145, 784. 99· Dupree, A. K., Goldberg, L. 1967, Solar abundance determination from ultraviolet emission lines, Solar Physics, I, 229. 196s, Silicon in the solar corona, Ann. Astrophys., 28, roo. Widing, K. G., Porter, J. R. 779 (also in 1964, IAU Symposium No. 23, Liege). IOI. de Jager, C. 1965, Solar X-radiation, Ann. Astrophys., z8, 12S (also in 1964, IAU Symposium No. 23, Liege). roz. Mandel'Shtam, S. L. 196s, On X-ray radiation of the quiet Sun, Ann. Astrophys., 28, 614 (also in 1964, IAU Symposium No. 23, Liege). IOJ. Mandel'Shtam, s. L. I96s, Space Sci. Rev., 4. s87.

OBSERVATIONS AU-DEHORS DE L'ATMOSPHERE TERRESTRE 993 I04. Fetisov, E. P. 1964, Solar coronal radiation shortward of 1oA, Soviet Astr., 8, 231, translated from Astr. Zu., 4I 1 299, 1964. I05. Mandel'Shtam, S. L., Prokudina, V. S., Tindo, I. P., Fetisov, E. P. 1965, X-rays from the quiet Sun, Cosmic Res., 3, 6o1, translated from the Russian Kosm. Issled., 3, 737, 1965. Io6. Zheleznyakov, V. V. 1965, The mechanism of y-ray emission of solar flares, Astr. Zu., 42. 96. 1964, The inverse Compton effect as a possible cause of the X-ray I07. Shklovsky, I. S. radiation of solar flares, Nature, 202, 276. 1965, Nature of solar X-ray emission, Soviet Astr., 8, 538, translated Io8. Shklovsky, I. S. from Astr. Zu., 4I 1 676, 1964. I09. Korchat, A. A. 1965, The solar flares of 28 September 1961, and 20 March 1958, Cosmic Res., 3, 751, 1965. no. Acton, L. W. 1964, Inverse Compton effect as a possible cause of the X-ray radiation of solar flates, Nature, 204, 64. III. Acton, L. W. 1965, Contribution of characteristic X-rays to the radiation of solar flares, Nature, 207, 737· II2. Fazio, G. G., Dolan, }. F. 1965, The gamma-ray spectrum of the Sun, Rev. Geophys., 3. 319. IIJ. Burgess, A. 1965, Dielectronic recombination in the corona, Ann. Astrophys., 28, 774 (also in 1964, IAU Symposium No. 23, Liege). II4. Burgess, A. Dielectronic recombination, 1965 Proc. Second Harvard-Smithsonian Conference on Stellar Atmospheres, p. 47· us. Goldberg, L., Dupree, A. K., Allen, J. W. 1965, Collisional excitation of autoionizing levels, Ann. Astrophys, 28, 589. ASTRONOMIE GALACTIQUE

(prepare par L. Houziaux)

I. Vehicules Spatiaux, Instruments et Projets !.1. Observations astronomiques sur orbite (OAO, U.S.A.) Aucun exemplaire de cette serie de plates-formes hautement stabilisees n'a pu encore etre mis en oeuvre avec succes. Le premier OAO emportait a son bord un ensemble de telescopes destines ala photometrie des etoiles et nebuleuses entre 1ooo et 42ooA. Le 'Celescope' de la Smithsonian Institution avait ete remplace par: (a) un detecteur de rayons gamma de haute energie (prepare par le M.I.T.), (b) un detecteur de rayons X, de Ia Lockheed Missiles and Space C 0 , (c) un detecteur de photons ayant des energies comprises entre 2000 et 18 ooo eV, mis au point par le Goddard Space Flight Center. Malheureusement, quelques heures apres la mise sur orbite, le 8 avril 1966, une temperature excessive a endommage les batteries du vehicule et la mission d'observation n'a pu etre executee. Une nouvelle tentative de lancement doit avoir lieu dans le courant de 1968. La charge utile sera composee des deux experiences prevues primitivement pour l'OAO I (Celescope du Smithsonian Astrophysical Observatory et photometrie ultraviolette des etoiles de l'Universite de Wisconsin). Deux autres vehicules OAO sont actuellement prevus. Le premier emportera un telescope Cassegrain de 36 pouces (91 em) destine a la spectrometrie a haute resolution d'etoiles, de nebuleuses et de galaxies. Cette experience est preparee par le Goddard Space Flight Center. L'Observatoire de l'Universite de Princeton (L. Spitzer et J. B. Rogerson) (I) se propose de placer sur orbite, en 1970, un telescope de 40 pouces (102 em) equipe d'un spectrographe d'un pouvoir resolvent de 104 et permettant la spectrophotometrie stellaire dans le domaine de loooA a 30ooA.

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La Nasa etudie actuellement la possibilite et !'interet d'effectuer des observations astronomiques a partir de satellites habites. Ce programme debuterait par une version de 1' 'Apollo Telescope Mount' (Programme d'Application Apollo) permettant !'observation des etoiles. En particulier, l'Observatoire de Princeton projette la realisation d'un telescope dont le pouvoir de resolution serait limite par la diffraction, et stabilise a o'!o1. II pourrait etre utilise soit par un observateur humain, soit de fa + 4 there is slight evidence for a dual (Mv, log m) relation. The observed (Mboh log m) relation is in good agreement with a series of main-sequence models with (X, Y) = (0·68, 0·30). Mrs A. E. Ringuelet-Kaswalder presented work by herself and J. Sahade on the determination of masses of Algol-type systems. Two methods are commonly used. Either one assumes that the primary component is a main-sequence star, or one assumes that the secondary component fills its equipotential lobe. In the second method, the mass-ratio derived is very sensitive to the assumed radius of the lobe, and therefore quite small photometric errors in the determination of the radius of the secondary component can lead to serious errors in the derived masses. Uniform use of the first method might eliminate the apparent anomaly of the R Canis Majoris systems. Plavec commented that the important point was to obtain good observations. For 19 out of 25 systems with well-determined elements, the two possible assumptions led to closely similar masses. Sahade replied that such agreement was to be expected in many cases, but the second method could fail badly; and, furthermore, it should be remembered that the equipotential surfaces refer to ideal stars and not to real ones. A later communication was received from V.P. Cesevic concerning recent work on eclipsing binaries in the U.S.S.R. V. Tabacnik (Odessa) has worked on the computation of elements by means of an electronic computer, and has applied his method to S Cancri. M. Kiperman and A. Sulberg (Odessa) have investigated the possibility of determining the non-linear coefficients of limb darkening, as discussed by Grygar. Cesevic himself has investigated the analysis of atmospheric eclipses with particular reference to the systems RW Trianguli and U Geminorum. He found much difficulty in the use of Linnell's tables and questions whether they can represent an observed light-curve at all. Poostylnik {Tartu) has also considered the problems of atmospheric eclipses, and computed tables based on theoretical values of the coefficient of absorption.

31. COMMISSION DE L'HEURE Report of Meetings PREsiDENT: H. M. Smith. SECRETARY: R.G. Hall. INTERPRETER: J. Bonanomi. First session, 23 August 1967

The loss was noted of two distinguished members of the Commission; A. Danjon and F. de Ia Puente. The President reported that the following people were proposed for membership in the Commission: G.M.R. Winkler, E. Proverbio, and G. Hemmleb. All were approved by the members. The President reported that the following two names were proposed as consulting members of the Commission: U. Adelsberger and J. Terrien. The transfer of L. Essen from member to consulting member was under discussion. This was approved. The President asked for comments on the Draft Report. There being none, the Report was approved. The Director of the B.I.H. reported on the activities of the B.I.H. which are given in the Draft Report. H. M. Smith, President of the Directing Board of the B. I. H., reported that it is not a function of the B.I.H. to report or note legal times of the various Governments. There was general · agreement that this was the case. The report of the Director of the B.I.H. was approved with thanks to B. Guinot. Resolutions that had been submitted to the President were then considered. A resolution from the French Commission of Geodesy and Geophysics concerning the form of the emission of time signals from HBG, Switzerland, was taken note of by the Commission. The resolution reads: Le Comite National Fran