Over the last decade we have witnessed a rapid change in our understanding of the late stages of stellar evolution. A major stimulus to this has been the synthesis of observational data from different wavebands of the electromagnetic spectrum. The advent of infrared astronomy has led to the discovery of many luminous. late-type stars obscured by their circumstellar dust envelope. Sources discovered in the IRC and AFGL infrared sky surveys were followed up by radio observa tions, leading to the widespread use of the OH and CO molecules as probes of the circumstellar envelopes. Advances in the technique of aperture synthesis have made possible observations with unprecedent resolving power, both in spectral-line and continuum. The success of the recent IRAS sky survey, with the detection of over 250,000 sources, brings the promise of even more exciting years ahead. This area of astronomical research is also blessed with the close collaboration between theorists and observers. New ideas are constantly being quantitatively tested by new data. Theoretical predictions are eagerly used as guides for further observations. This conference was initiated with the following objective: bring together workers in optical, infrared, radio and theoretical astronomy and let them confront each other. Based on the post-conference res ponses we received, many of the participants have indeed found this Workshop a stimulating experience. The Workshop on the Late Stages of Stellar Evolution was held from 2-5 June 1986 in Calgary, Canada."

ThlS volume contalns a serles of lectures presented at the NATO Advanced Study Instltute on Hlgh Energy Phenomena Around Collapsed Stars, held ln Cargese, CorSlca from September 2 tlll Septemcer 13, 1985. The course was planned ln collaboratlon wlth a SClentlflC Organiz ing Commlttee (C. Cesarsky, France; A. Lyne, U.K.; D. Plnes, USA; J. Trlimper, W. Germany; E. Van den Heuvel, The Netherlands and L. Wolt]er, E.S.O., Mlinlch) and was fully supported by the NATO SClentlflc Affalrs Dlvlsion. It was organized wlth the alm of provldlng students and young researchers with an up-to-date account on the subject of galactlc hlgh energy astrophyslCS and was attended by about 60 researchers from many countrles. The lectures and seminars dld represent a complete coverage of our present knowledge and understandlng of Supernovae, Supernovae Remnants, Pulsars, sources of hlgh energy photons and partlcles. Most of them are reproduced ln thlS volume although unfortunately a few speakers chose not to submlt thelr text Slnce they felt that the materlal was already amply avallable ln the eXlstlng llterature. I wlsh to express my gratltude to the SClentlflc Affalrs Dlvislon of the North Atlantlc Treaty Organlzatlon for the generous support glven to the Instltute and to the lecturers and particlpants who contributed so much to the success of the course."

The idea to hold a Symposium on Star Forming Regions in Japan, be fore or after the New Delhi General Assembly of the IAU, originated in 1981. One of the main reasons was that the 45-m telescope was expected to be inoperationby 1982. In addition it was considered that Japan had been very active in the theory of star formation as well as in mm and IR observations of star forming regions. At the Patras General Assembly of the IAU the issue was brought up for discussion at meetings of Commis sions 34 (Interstellar Matter) and 40 (Radioastronomy), the former agreed to sponsor the Symposium, while the latter agreed to co-sponsore it. The IAU Executive Committee accepted the proposal to hold the Symposium on September 1983. The Symposium was held in Tokyo on 11-15 November 1985, just before the New Delhi General Assembly. It was attended by 250 scientists from 18 countries, and 212 papers were presented. The Scientific Organizing Committee elaborated a superb program of invited and review presentations. The Conference consisted of oral and poster sessions. The oral sessions included review papers, invited papers and a few of the contributed papers; after each presentation a discussion was held. The poster ses sions included most of the contributed papers and were very well attended. We consider that the scientific goals of the meeting were amply achieved and we express our thanks to all the participants and specially to the members of the SOC for making them possible."

The chemical processes of formation and destruction of molecules have been found to be widespread in astronomical scenario. It occurs in comets, planetary atmospheres including ionospheres, early solar system, stellar atmospheres, circumstellar shells, interstellar clouds, and possibly even in the early universe. Physical conditions are naturally different in the different situations, but there is unity in the underlying physics and chemistry in this diversity. Therefore, a need was felt to gather together astronomers, physicists and chemists in these and allied interdisciplinary fields to enrich each other with their experiences. This International Astronomical Union Symposium No.120 on Astrochemistry, the proceedings of which is this, has partially fulfilled this need. This symposium, held at the beautiful and scenic sea resort of Goa, India, between December 3-7, 1985, under the sponsorship of the IAU Commission No.34 and co-sponsorship of IAU Commissions 14, 15, 29 and 36, was attended by 116 registered participants with 19 accompanied guests from 19 countries. The scientific programme comprised of 34 review talks, 15 invited talks and 47 contributed poster papers, clima xed by a grand finale by Professor A. Dalgarno with an overview of th whole symposium. The Symposium covered almost all aspects of astro chemistry from the early universe to comets and meteorites, except iono spheres and planetary atmospheres. Basic atomic and molecular physics, experimental and observational results, and theoretical calculations and modelling, all were stressed."

This is the first time that the International Astronomical Union has held a symposium on objects of totally unknown nature. In fact. M. Rees has pointed out that the mass of the individual particles that make up the dark matter is unknown to > 70 orders of magnitude. Since dark matter appears to make up ~ 90 % of the mass of the Universe. it presents us with one of the most fundamental problems in astrophysics. IAU Symposium 117 on Dark Matter in the Universe was held on June 24 - 28. 1985. Our hosts were Princeton University and the Institute for Advanced Study. which together form one of the most active centers of work on the dark matter problem. There were ~ 190 participants from 16 countries. These proceedings include the 31 review and invited papers. 72 of the 85 poster papers. and the two general discussions. The idea that the Universe might contain much more mass than we see in gas. stars and their remnants has been with us for over 50 years. In 1933. F. Zwicky pointed out that the Coma Cluster could be in equilibrium at the large observed velocity dispersion only if a great deal of unseen matter were present. However. in the absence of other evidence. the idea of "dark matter" was not widely pursued.

This volume contains papers presented at IAU Colloquium No. 90. at the Crimean Astrophysical Observatory in May of 1985. A few additional contributions are included from authors who for various reasons were unable to attend the meeting. Four years have passed since the last major international conference on chemically peculiar stars of the upper main sequence was held in Liege. Belgium in 1981. Previous conferences were held in 1975 (Vienna. Austria) and in 1965 (Greenbelt. Maryland. USA). As the proceedings of this Colloquium show. the recent availability of ultraviolet spectra of large numbers of normal and chemically peculiar A and B stars is having a major impact on the way we study these objects. and has led to many new. exciting and unanticipated results. Simultaneously. the more traditional study of optical spectra has been advanced through the increasing use of very high spectral resolution with high signal-to-noise detectors. The chemically peculiar (CP) stars on the upper main sequence belong in the standard framework within which we understand stellar evolution and the history of matter. Recent work has made it clear that the unusual chemistry and magnetic structure of these objects is of relevance across the broad domain of stellar astronomy. from the upper main sequence to horizontal branch stars and white dwarfs. Metal poor (J>. Boo) as well as metal rich (Ap. Am) stars are an integral part of the picture.

It was a general feeling among those who attended the NATO / ARW meeting on the Galaxy Distances and Deviations from Universal Expansion, that during the week in Hawaii a milestone had been passed in work on the distance scale. While not until the last minute did most of the participants know who else would be attending, no one was displeased with the showing. As it turned out, scarcely a single active worker in the field of the distance scale missed the event. Few knew all of the outstanding work that was to be revealed, and/or the long-term programs that were to be encapsulated in the first few days. Areas of general agreement were pinpointed with candid speed, and most of the discussion moved on quickly to new data, and areas deserving special new attention. As quickly as one project was reported as being brought successfully to a close, a different group would report on new discoveries with new directions to go. New data, new phenomena; but the sentiment was that we were building on a much safer foundation, even if the Universe was unfolding in a much more complex and unexpected way than was previously anticipated. In editing these proceedings a decision was made well in advance of the Meet ing that no attempt would made to record the discussion. This was done for many reasons."

Proceedings of the 116th Symposium of the International Astronomical Union, held at Porto Heli, Greece, May 26-31, 1985

Proceedings of the 116th Symposium of the International Astronomical Union, held at Porto Heli, Greece, May 26-31, 1985

The idea to hold a conference on the Evolution of Close-Binary X-ray sources grew in the summer of 1984. At that time we were hoping that some new results would be harvested in the months to come which would stimulate further work. We were particularly looking towards the Euro pean X-ray Observatory, EXOSAT, for new contributions. How lucky we were; quite unexpected developments took place. Just prior to the conference, quasi-periodic oscillations (now known as QPO) were discovered in three bright low-mass X-ray binaries: GX 5-1, Sco X-1, and Cyg X-2. They played an important role at the meeting. The possibility that QPOs imply a neutron star magnetic dipole field, and a neutron star rotation period in the millisecond range, received a lot of attention. This is not surprising, as it lends support to the idea, suggested earlier, that the 6-msec binary radio pulsar PSR 1953+29 evolved from a stage in which it was a bright low-mass X-ray binary. There was special interest in the possibility of white dwarf collapse into a neutron star. This is a. particularly attractive way to form the bright low-mass X-ray binaries, often referred to as galactic bulge sources. It would allow for the possibility of a very young neutron star in a very old binary system. The relatively high magnetic fields that one could infer from QPO could then be explained."

As it was said by one of the participants to this workshop" In our attempts to understand the spectral evolution of galaxies, we are fortunate indeed to have the ability to look back in time and observe galaxies as they were billions of years ago. Perhaos in no other discipline is it possible to gain such a direct view to hJstory. The galaxies we seek to study are remote, their light faint, and thus only recently has it become technicaJlv feasible to sample the spectra of normal luminosity galaxies at lookback times of five billion years or more" .... or, perhaps. even to see galaxies in the process of their formation. or shortly afterwards. This fourth workshop organized by the "Advanced School ot Astronomy was indeed centered on the "Spectral Evolution of Galaxies." on reviewing and discussing the relevant astrophysical processes and on assessing our current ability to model and understand the evolution of stellar populations. Following an opening session dealing with some outstanding questions of galaxy evolution. Session I addressed the specific problems of galaxy and star formation processes. topics of uncertainty and controversy to which IRAS observations may give novel perspectives. The properties of stellar populations in the local group of galaxies formed the basis of Session II. Session III dealt with the fundaments of the theory of spectral and photometrical evolution of stellar populations. and with recent developments in the theory of stellar structure. a necessary step to model and understand galactic evolution.

Proceedings of International Meeting held in Trieste, Italy, April 10-13, 1985

Adriaan Blaauw; Emeritus Professor of Astronomy at the Universities of Groningen and Leiden, former Directo.r of the Kapteyn Laboratory and of the European Southern Observatory, celebrated his 70th anniversary on 12 April 1984. To mark this event, an international Symposium was con- vened on the subject "Birth and Evolution of Massive Stars and Stellar Groups", a subject which has played the leading role in Blaauw's scien- tific research. The present volume contains the Scientific Proceedings of that Symposium. The meeting was organized by a Committee consisting of: W.H.W.M. Boland (Secretary), W.N. Brouw, W.B. Burton, E.P.J. van den Heuvel, H. van der Laan and H. van Woerden (Chairman). Together, these six persons represented the Executive Committees of the Netherlands Foundation for Astronomical Research (ASTRON) and the Netherlands Foundation for Radio Astronomy (RZM), two organizations in which Blaauw has held key offices. The scientific program was planned in full consultation with Adri- aan Blaauw himself. Only section 5, "A profile of Adriaan Blaauw", was kept secret to him. The other four sections: Structure of star-forming regions, Stellar content of young groups, Evolution of massive stars, and Extragalactic perspective on star formation, each represent an im- portant aspect of the overall theme of the Symposium. The program in- cluded 6 major review papers, 18 invited papers, 17 contributed papers, some of which were given as posters, and ample time for discussion.

This volume is the product of Lecturers in the fourth Course of the International School of Cosmic-Ray Astrophysics held at the Ettore Majorana Center in Erice, Sicily in November, 1984. The Course, devoted to "Cosmic Radiation in Contemporary Astrophysics," was concurrently a NATO-sponsored Advanced Study Institute (ASI). Cosmic-ray research is in a state of ferment. Precise measure ments - some made with instruments aboard sattelites and space probe- have been confronting models and theories with severe constraints. The observations of gamma-ray sources, notably Cyg X-3, at energies up to 16 10 eV, have opened up tantalizing possibilities of direct source iden tification. This ASI was devoted largely to interdisciplinary phenomena in cosmic-ray astrophysics whose understanding requires input from the other channels in astronomy. It explored the ways in which progress in cosmic-ray science might clarify phenomena observed in related disciplines. In trying to achieve this aim, we assembled a staff of lecturers representing various astrophysical specialties, such as radio astronomy, optical astronomy, X-ray astronomy, gamma-ray astronomy, and of course, particle astronomy (i.e., cosmic radiation). Students and other participants were likewise drawn from diverse backgrounds. Vigorous discussions enlivened almost every session."

IAU Symposium No. 111, "Calibration of Fundamental Stellar Quanti- ties", was held at Villa Olmo, Como, Italy, on May 24-29, 1984. Meet- ings held in the past ten years on related topics include: IAU Symposium No. 109, '*Astrometric Techniques", held at the University of Florida in Jan. , 1984, "The MK Process and Stellar Classification", held at the University of Toronto in June, 1983, "Stellar Absolute Energy Distri- butions", an unpublished Joint Meeting (Commissions 25 and 45), held at the General Assembly of the IAU in Patras, Greece in August, 1982, IAU Colloquium No. 62, "Current Techniques in Double and Multiple Star Re- search", held at Northern Arizona University in May, 1981, the ESO Work- fl shop: "Methods of Abundance Determination for Stars , held in Geneva in March, 1980, "Problems of Calibration of Multicolor Photometric Sys tems", held at Dudley Observatory in March, 1979, IAU Colloquium No. 48, "Modern Astrometry", held at the University of Vienna in Sept. , 1978, IAU Colloquium No. 50, "High Angular Resolution Stellar Interferometry" held at the University of Maryland in Aug. , 1978, "Spectral Classifice. - tion of the Future", held at the Vatican in July, 1978 and IAU Sympos- ium No. 72, "Abundance Effects in Classification", held at the Univer- sity of Lausanne in July, 1975. The present meeting was the first to cover the broad range of the calibration of fundamental stellar qU8T". ti- ties in one meeting. Nine commissions of the IAU co-sponsored the meeting.

Red giant and supergiant stars have long been favorites of professional 6 and amateur astronomers. These enormous stars emit up to 10 times more energy than the Sun and, so, are easy to study. Some of them, specifically the pulsating long-period variables, significantly change their size, brightness, and color within about a year, a time scale of interest to a single human being. Some aspects of the study of red giant stars are similar to the study of pre-main-sequence stars. For example, optical astronomy gives us a tantalizing glimpse of star forming regions but to really investi gate young stars and protostars requires infrared and radio astronomy. The same is true of post-main-sequence stars that are losing mass. Optical astronomers can measure the atomic component of winds from red giant stars that are undergoing mass loss at modest rates 6 (M $ 10- M9/yr.). But to see dust grains and molecules properly, 5 especially in stars with truly large mass loss rates, ~ 10- M9/yr, one requires IR and radio astronomy. As this stage of copious mass loss only lasts for ~105 years one might be tempted to ask, "who cares?".

This book is the proceedings of a workshop on stellar continuum radio astronomy that was held in BoUlder, Colorado on August 8-10, 1984. Although it was originally intended to be a small workshop with participants mainly from North America, it evolved to a workshop with 72 partiCipants from twelve countries (U.S.A. 52, Canada 3, the Netherlands 3, United Kingdom 3, Australia 2, Ireland 2, Italy 2, France 1, Mexico 1, Switzerland 1, West Germany 1, and U.S.S.R. 1). This workshop was sponsored by the Joint Institute of Laboratory Astrophysics (JILA) and the University of Colorado. In order to preserve a workshop atmosphere, while still presenting both extensive reviews and contributed papers, an experimental format was adopted. All contributed papers related to the topiCS of the day were presented in poster form in the early morning and were accessible all day. During each morning (or afternoon) session review papers were presented, followed by a coffee break in the poster area adjacent to the conference room. Then the review papers and contributed papers were discussed for roughly one and a half hours. The last session was devoted to invited panel papers and discussion of current and future problems in the field of stellar radio astronomy.

The emphasis in these proceedings of lAD Symposium No. 113, Dynafrri-, ' s of Star Clusters. and.. .Le. mab rPIHlon for orZ'lnizinp: thE" symposium in the spring of 1984, was the rapid increase during the preceeding year in our understanding of core collapse. The last I.A.D. Symposium to discuss the dynamics of star clusters at length was No.69, Dynamics of Stellar Systems held in Besan on in 1974. For a few years afterwards, globular clusters receiveu much attention due to the discovery of X-ray bursters and the mounting evidence that X-ray sources in globular clusters were formed in completely different ways than those within our galaxy. Globular clusters, which until this time had a reputation for sedate old age, turned out to lead violent private lives at high energies. However, in the early 80's globular clusters seemed to lose some of the glamor of the 70's. The grand speculations of heavy black holes lurking in their centers had to make way for a variety of observational evidence which indicated that the X-ray sources are low-mass close binaries instead. But, though dynamical fashion turned to heavy galac tic halos and so on, some of the unsolved theoretical problems regard ing the evolution of star clusters kept their fascination for a number of relatively isolated workers. After several years of inconspicuous labor, a number of preprints suddenly appeared in the spring of 1983 that studied the evolution of globular clusters after core collapse."

The idea of this colloquium was first put forward by Prof. P. Keenan when he visited the Centre de Donnees Stellaires, in September 1982. Dr. A. Florsch, Director of the Strasbourg Observatory, kindly accepted to field it at Strasbourg. The scientific organization of the colloquium was in charge of a Committee chaired by Prof. P.C. Keenan and composed by M. Feast, A. Florsch, B. Gustafsson, D. Harmer, M. Jaschek (secretary), R. McClure, A. Maeder, W. Straizys and T. Tsuji. The members of the Committee helped to translate the idea into a very successful meeting. It should be added that this colloquium was the first meeting devoted to late-type peculiar stars. The program was organized by sessions devoted to the following topics : taxonomy, photometric properties, distribution and space motions, chemical com- position, model atmosphere, binary systems and evolutionary tracks. Each session started with a review paper, followed by contributed papers presented as posters. The different sessions were chaired by W. Bidelman, R. Cayrel, Ch. Cowley, A. Heck, H.R. Johnson, J.P. Kaufmann and T. Tsuji, who did an excellent job. The President of the "Louis Pasteur University of Strasbourg", Prof. H. Duranton, welcomed the participants to the University where the sessions were held; Dr. A. Florsch welcomed the participation on be.balf of the French astrono- mical community and Prof. P. Keenan spoke on behalf on the Scientific Organizing Committee.

In June 1983 the Astronomical Institute of the State University of Groningen, founded by Kapteyn about 100 years ago, celebrated its one-hundredth anniversary. At the suggestion of its Chairman, R.J. Allen, the Kapteyn Institute invited the International Astronomical Union to mark the centenary by holding a Symposium on "The Milky Way Galaxy". The purpose of the Symposium was to review recent progress in the study of our Galaxy, to define current problems, and to explore prospects for future development. The Symposium programme would emphasize the large-scale characteristics of our Galaxy, and highlight both the historical development of our understanding of the Milky Way Galaxy and the importance of studies of external galaxies to this understanding. The Symposium was sponsored by four IAU Commissions: 33 (Structure and Dynamics of the Galactic System), 28 (Galaxies), 34 (Interstellar Matter) and 41 (History of Astronomy). The Scientific Organizing Committee, listed on page xviii, represented a broad range of nationalities and of expertise, including two historians of science. A meeting of the Committee, held during the IAU General Assembly at Patras, provided an excellent opportunity to discuss plan and format of the Symposium, topics and speakers; thereafter, the-Committee was regularly consulted by letter and telephone. IAU Symposium 106 was held at Groningen on 30 May - 3 June 1983, in the new building occupied by the Kapteyn Institute since January 1983. There were about 200 participants, coming from as many as 25 countries.

"If simple perfect laws uniquely rule the universe, should not pure thought be capable of uncovering this perfect set of laws without having to lean on the crutches of tediously assembled observations? True, the laws to be discovered may be perfect, but the human brain is not. Left on its own, it is prone to stray, as many past examples sadly prove. In fact, we have missed few chances to err until new data freshly gleaned from nature set us right again for the next steps. Thus pillars rather than crutches are the observations on which we base our theories; and for the theory of stellar evolution these pillars must be there before we can get far on the right track. " These words written by Martin Schwarzschi1d in his famous book en titled "Structure and Evolution of the Stars"(1958) remind us how necessary and fruitful is the interplay of stellar evolution theory and observations. Clearly, observations are the great censor by their possibility of confirming or contradicting theoretical constructions. In addition, they have a driving role: new and sometimes unexpected facts may give rise to progressive ideas and stimulate further theoretical developments. In turn, theory, in its major role of sifting out and placing the facts in a logical sequence based on physical laws, must also be predictive and indicate new and pertinent observations to be undertaken."

"If simple perfect laws uniquely rule the universe, should not pure thought be capable of uncovering this perfect set of laws without having to lean on the crutches of tediously assembled observations? True, the laws to be discovered may be perfect, but the human brain is not. Left on its own, it is prone to stray, as many past examples sadly prove. In fact, we have missed few chances to err until new data freshly gleaned from nature set us right again for the next steps. Thus pillars rather than crutches are the observations on which we base our theories; and for the theory of stellar evolution these pillars must be there before we can get far on the right track. " These words written by Martin Schwarzschi1d in his famous book en titled "Structure and Evolution of the Stars"(1958) remind us how necessary and fruitful is the interplay of stellar evolution theory and observations. Clearly, observations are the great censor by their possibility of confirming or contradicting theoretical constructions. In addition, they have a driving role: new and sometimes unexpected facts may give rise to progressive ideas and stimulate further theoretical developments. In turn, theory, in its major role of sifting out and placing the facts in a logical sequence based on physical laws, must also be predictive and indicate new and pertinent observations to be undertaken."

I.A.U. symposium No. 110 on VLBI and Compact Radio Sources was held in Bologna, Italy from June 27 to July 1, 1983. 166 participants from 19 countries were registered and 106 invited and contributed papers were registered. The scientific presentations and discussion concentrated on VLBI observation and interpretation of galactic and extragalactic radio sour ces, including topics as diverse as quasars and galactic nuclei, inter stellar masers, pulsars, and astrometry. Geodetic applications and tech nical development were treated only briefly, as these topics have been the subject of other recent international symposia. Since the first VLBI observations in 1967, sensitivity, resolution, and image quality have improved dramatically. Radio maps shown at the symposium were of comparable quality to conventional synthesis maps be ing made at the time of the first VLBI experiments 15 years ago, but with a resolution more than a factor of 1000 better. We wanted to accommodate the large number of contributed papers in this rapidly developing field, but there was inadequate time for normal oral presentations and discussion. We therefore asked that all contrib uted papers be put on display for at least 24 hours prior to a brief oral summary. A question and discussion period followed groups of oral pres entations on the same or similar topic. In this way the opportunity for interactive discussion, not available in conventional poster displays, was preserved."

I.A.U. symposium No. 110 on VLBI and Compact Radio Sources was held in Bologna, Italy from June 27 to July 1, 1983. 166 participants from 19 countries were registered and 106 invited and contributed papers were registered. The scientific presentations and discussion concentrated on VLBI observation and interpretation of galactic and extragalactic radio sour ces, including topics as diverse as quasars and galactic nuclei, inter stellar masers, pulsars, and astrometry. Geodetic applications and tech nical development were treated only briefly, as these topics have been the subject of other recent international symposia. Since the first VLBI observations in 1967, sensitivity, resolution, and image quality have improved dramatically. Radio maps shown at the symposium were of comparable quality to conventional synthesis maps be ing made at the time of the first VLBI experiments 15 years ago, but with a resolution more than a factor of 1000 better. We wanted to accommodate the large number of contributed papers in this rapidly developing field, but there was inadequate time for normal oral presentations and discussion. We therefore asked that all contrib uted papers be put on display for at least 24 hours prior to a brief oral summary. A question and discussion period followed groups of oral pres entations on the same or similar topic. In this way the opportunity for interactive discussion, not available in conventional poster displays, was preserved."

Proceedings of IAU Symposium No. 108 held in Tubingen, West Germany, September 5-8, 1983"