A complete and comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The text presents an overview of the models developed to explain the stability, dynamics and evolution of the stars, and great care is taken to detail the various stages in a star's life. The authors have succeeded in producing a unique text based on their own pioneering work in stellar modeling.
Since its publication, this textbook has come to be considered a classic by both readers and teachers in astrophysics. This study edition is intended for students in astronomy and physics alike.

In the early summer of '89 a very informal meeting on the bulge of our Galaxy was held in Leiden. During that meeting Michael Rich proposed to hold a more properly organised symposium on "Galactic Bulges" in a few years time. After some discussion a Scientific Organising Committee was founded and after some manoeuvring a chairman was chosen, a local organiser was assigned and two editors were given instructions. A good thing about the location of the meeting was that Ghent is a very beautiful city and had never before hosted an IAU symposium. It could be that this, plus the fact that he is a very keen amateur astronomer led H. M. the King of Belgium to offer his patronage to the meeting - an offer that we gratefully and - we hope - gracefully accepted. The meeting took place at a resort some 15 km outside Ghent. Most participants were housed on the premises - a very convenient situation. This feeling of togeth erness made up for the small shortcomings of the lecture room, which is normally used as a sports hall. The weather was fair, except on the day of the barbecue when pouring rain forced us to go inside.

This book contains the proceedings of the first large IAU Symposium dedicated to the bulges of spiral galaxies. Detailed attention is paid to the bulge of the Milky Way, one of the major building blocks of this system. Topics include the definition of the bulge in our Galaxy and its relation to the so-called spheroid. Discussions are presented regarding the stars contained in this bulge, their astrophysical properties, their motions and the metallicity variations which appear to be present. The possible existence of a bar in the bulge and its origin and future are also examined. The same topics are discussed in less detail for the bulges of other galaxies.

In July 1992, over 300 astronomers attended the Third Tetons Summer School on the subject of "The Environment and Evolution of Galaxies". This book presents 28 papers based on invited review talks and a panel discussion on "The Nature of High Redshift Objects". The major themes include: the interstellar and intergalactic medium, galaxy formation and evolution, cooling flows, quasars and radiation backgrounds, and interactions between galaxies/AGNs and their environment. Recent advances with the ROSAT, COBE and Hubble Space Telescope are discussed, together with current theoretical developments. The tutorial nature of the papers should make this book a useful supplement for professional astonomers, graduate students, and senior undergraduates. As with previous Tetons conferences, this book provides both the current state of observational and theoretical research and material complementary to courses in extragalactic and interstellar astrophysics.

In the last few years great improvements in the study of stellar jets and bipolar outflows have been achieved, both observationally and theoretically. High resolution observations at various frequencies (radio, IR, optical and X-ray) of these features in different types of objects have shown a large variety of morphologies at all scales often revealing contrasting symmetries which do not allow straightforward kinematic interpretations valid for all cases. In particular, at present, it seems very difficult to give a statistical definition of what the "standard properties" of jets and bipolar outflows are. On the theoretical side, the identification of physical processes capable of producing the observed rich morphological variety of jets and bipolar outflows and supporting them over long lifetimes is still controversial. Furthermore several models are actively discussed in an attempt of reaching a complete understanding of the phenomenon. The workshop provided an unique opportunity for both observers and theoreticians to gather together and produce an updated and exhaustive picture of the field. In addition the meeting has been enriched by the presentation of some works on jets in external galaxies. This topic was focused on what people working on stellar jets could learn from colleagues working on extragalactic jets and vice versa. Invited papers were prepared with the aim of giving the state of the art about scientific subjects; contributed papers and some selected poster papers presented, on the contrary, very recent results in the various fields.

In July 1992, over 300 astronomers attended the Third Tetons Summer School on the subject of The Environment and Evolution of Galaxies'. This book presents 28 papers based on invited review talks and a panel discussion on The Nature of High Redshift Objects'. The major themes include: the Interstellar and Intergalactic Medium, Galaxy Formation and Evolution, Cooling Flows, Quasars and Radiation Backgrounds, and Interactions between Galaxies/AGNs and their Environment. Recent advances with the ROSAT, COBE and Hubble Space Telescope are discussed, together with current theoretical developments. The tutorial nature of the papers make this book a valuable supplement for professional astonomers, graduate students, and senior undergraduates. As with previous Tetons conferences, this book provides both the current state of observational and theoretical research and material complementary to courses in extragalactic and interstellar astrophysics.

More than two centuries have elapsed since the story of interacting binary stars began with the rediscovery of the variability of Algol by John Goodricke and the interpretation he proposed for explaining the regular periodic brightness variations which he found. Over this long span of time our knowledge about these systems has been growing, and we have now reached a fairly good understanding of the structure and behaviour of this interesting group of objects. This book contains a timely summary of our present knowledge of interacting binary stars. The chapters have been written by distinguished scientists who have done relevant research in the field of interacting binary stars.

Planetary nebulae are a keystone for the understanding of the evolution of stars, for deep insights into the physical processes prevailing in highly excited dilute nebulae, and for the chemical evolution in galaxies. These objects, displaying an intriguing morphology, have a `short' lifetime of a few tens of thousands of years, and have become one of the best studied classes of celestial sources. However, despite large and successful efforts from both the observational and theoretical side, planetary nebulae still keep some of their secrets (like the widely unknown distances) and will undoubtedly also be objects of thorough investigations in the years to come.

The motivation for the workshop on which this book is based was the discovery in recent years of a large number of binary and millisecond radio pulsars, in the galactic disk as well as in globular star clusters, the oldest stellar systems in our galaxy. These discoveries have revolutionized our thinking on many aspects concerning the interior structure and evolution of neutron stars, and have revived the interest in the study of neutron star physics in general. In this book some three dozen of the world's experts in the field of radio pulsars, X-ray binaries, stellar evolution, neutron star interiors and stellar dynamics review the latest observational discoveries as well as the current theoretical thinking on the formation and physics of binary X-ray sources and of the binary and milli-second pulsars. These include discoveries such as that of the elevent millisecond pulsars in the globular cluster 47 Tucanae, the relativistic effects in the new double neturon star system PSR 1534+12 and spectacular results from Germany's ROSAT X-Ray Observatory.

Our view of the Galaxy has recently been undergoing an increasing divergence from the traditional standpoint. In this book, ten authors discuss in eight chapters how the conceptions of the Milky Way have moved in new directions. Starting with the inner parsec and the Centre of the Galaxy, the book gradually moves on to the bulge and its relation to the globular clusters and to the disk, of which the presence of a bar is argued. A new look on the HI distribution in the disk, a synthesis of molecular line surveys and the study of stellar populations are discussed in the last three chapters.

One approach to learning about stellar populations is to study them at three different levels of resolution. First in our own galaxy; secondly from nearby galaxies where stars can still be resolved; and thirdly in remote galaxies in which the stellar population can only be studied in integrated light. This International Astronomical Union Symposium covered the range of galaxies in its study of their stellar populations. Interspersed with theoretical papers, the observational papers provide a presentation of the progress that has been made in the field.

Clusters and superclusters of galaxies are the largest objects in the Universe and are the subject of intense observational study at a variety of wavelengths, from radio to X-ray which has provoked much theoretical debate and advanced the understanding of the recent evolution of the large-scale structure the universe. The subject is reviewed in this volume by researchers who lectured at a NATO Advanced Study Institute held in Cambridge in July 1991. Much of the material is presented in a pedagogical manner and should be useful to scientists, astronomers and graduate students interested in extragalactic astronomy.

The previous Saas-Fee Advanced Course dedicated to the interstellar medium took place in 1972. The tremendous scientific advances that have occurred in this field since then, in particular owing to the availabihty of receivers working at completely unexplored wavelength bands, fuUy justified a new set of lectures. As a consequence, the members of the Swiss Society for Astrophysics and As tronomy voted that "The Galactic Interstellar Medium" should be the subject of the 1991 course. The 21st Saas Fee Advanced Course took place in Les Diablerets from 18 to 23 March 1991, gathering together about 80 participants from all over the world, but mostly from Europe. According to a rule that has proved to lead to success, but also to chal lenge the lecturers' energy, the format of a Saas-Fee Advanced Course consists traditionally of 28 lectures of 45 minutes which take place in the morning and late afternoon, leaving ample time for discussions, self-study, hiking or skiing. Despite the inordinate work load imposed, this year's lecturers felt that the subject was sufficiently dense to increase the lecture time by 1/3! This proved judicious and left more time for questions and discussions during the lectures.

This book contains the proceedings of IAU Symposium No. 151 `Evolutionary Processes in Interacting Binary Stars,' which was held from 5 to 9 August 1991 in Cordoba, Argentina. The primary aim of this conference was to review and evaluate our current understanding of the evolutionary processes in wide variety of interacting binary stars from their births to their deaths. Subjects included the formation of binaries, mass flow and transfer, accretion processes, and binaries with collapsed components, such as novae, X-ray binaries and binary pulsars. As the field covered is both broad and diverse, there were in all thirty-seven invited talks; sixty-two contributed papers were also presented. In addition, these proceedings contain comments from a panel discussion of the major unsolved problems of interacting binary stars.

This book contains the proceedings of IAU Symposium No. 151 Evolutionary Processes in Interacting Binary Stars, ' which was held from 5 to 9 August 1991 in Cord ba, Argentina. The primary aim of this conference was to review and evaluate our current understanding of the evolutionary processes in wide variety of interacting binary stars from their births to their deaths. Subjects included the formation of binaries, mass flow and transfer, accretion processes, and binaries with collapsed components, such as novae, X-ray binaries and binary pulsars. As the field covered is both broad and diverse, there were in all thirty-seven invited talks; sixty-two contributed papers were also presented. In addition, these proceedings contain comments from a panel discussion of the major unsolved problems of interacting binary stars.

The Andromeda Galaxy, or M31, is an attractive galaxy for astronomers. It is close to us, it is of about the size of our galaxy, it provides some intriguing observational puzzles because the galaxy is nearly edge-on, and many objects can be studied in detail, because they are still sufficiently bright. With the current developments in instrumentation with which increasingly detailed studies of the Andromeda Galaxy can be made, this book provides a solid foundation for the start of new observations. This book is a mine of information about M31. It can be used as a reference by insiders, and at the same time it provides easy access for newcomers to the field.

Classical stellar evolution theories have undergone some drastic changes in recent decades. New insights into the development of stellar interiors were obtained from studying stars in various stages of their lives, as well as with the help of fast computers, which gave a boost to the branch of numerical modelling of stellular structure and evolution. This book is divided into two parts. The first part deals with the general aspects of stellular structure and evolution including a chapter on numerical modelling. The second part deals with specific evolutionary aspects of single and binary stars with a variety of masses. The last chapter gives several models of stars with specific masses. The book is intended as an introduction for students, as well as a reference for researchers.

Classical stellar evolution theories have undergone some drastic changes in recent decades. New insights into the development of stellar interiors were obtained from studying stars in various stages of their lives, as well as with the help of fast computers, which gave a boost to the branch of numerical modelling of stellular structure and evolution. This book is divided into two parts. The first part deals with the general aspects of stellular structure and evolution including a chapter on numerical modelling. The second part deals with specific evolutionary aspects of single and binary stars with a variety of masses. The last chapter gives several models of stars with specific masses. The book is intended as an introduction for students, as well as a reference for researchers.

The morphological scheme devised by Hubble and followers to classify galaxies has proven over many decades to be quite effective in directing our quest for the fundamental pa rameters describing the extragalactic manifold. This statement is however far more true for spirals than for ellipticals. Echoing the concluding remarks in Scott Tremaine's sum mary talk at the Princeton meeting on Structure and Dynamics of Elliptical Galaxies, "the Hubble classification of spirals is useful because many properties of spirals (gas con tent, spiral arm morphology, bulge prominence, etc. ) all correlate with Hubble time. By contrast, almost nothing correlates with the elliptical Hubble sequence El to E7. " During the last few years much effort has been put into the search for a more meaningful classification of ellipticals than Hubble's. Concomitantly, forwarded by some provocative conjectures by R. Michard, the classical question of whether E galaxies form a physically homogeneous family has been brushed up once more. Results of these and other parallel studies look rather promising and point to suture part of the dichotomy between ellipticals and disk galaxies which had become popular in the early eighties, owing to dynamical arguments. At the same time it appears more and more clear that, besides the usual genetic varieties of galaxies, products of environmental evolution must also be contemplated in building our modern picture of the "reign of galaxies" . The above considerations prompted us to solicit Prof."

One approach to learning about stellar populations is to study them at three different levels of resolution. First in our own Galaxy; secondly from nearby galaxies where stars can still be resolved; and thirdly in remote galaxies in which the stellar population can only be studied in integrated light. This IAU Symposium covered the entire range of galaxies in its study of their stellar populations. Interspersed with theoretical papers, the wealth of observational results provides an important state-of-the-art presentation of the progress that has been made in this field.

Highly ionized atoms in the general interstellar gas of the galactic disk were first detected through interstellar absorption line observations of 0 VI with the Copernicus satellite (Rogerson et al. 1973). Survey measurements by Jenkins (1978) of interstellar 0 VI absorption toward 72 stars demonstrated the general presence of 0 VI in the interstellar medium of the galactic disk. This researcIi. and parallel observational studies of the soft X-ra}' background (Williamson et al. 1974; McCammon et al. 1983; Marshall and ClarK 1984) provided direct evidence for the existence of hot low density gas in the mterstellar medium of the galactic disk. The extension of the aDsorption line studies to the distant gas of the galactic halo required the launch of the International Ultraviolet Explorer (IUE) satellite in 1978. The first measures of highly ionized gas m the galactic halo were obtained with the IDE when it was used to record high resolution spectra of bright stars in the Large Magellanic Cloud (Savage and de Boer 1979). Those early spectra revealed the presence of absorption by Si IV and C IV in the galactic nalo and have been followed by a number of surveys with IUE of nighly ionized gas in the galactic disk and halo (Savage and de Boer 1981; Pettini and West 1982; Savage and Massa 1987). The study of UV emission from highly ionized gas in the halo has progressed more slowly because of the intrinsic faintness of the emission.

I. Initial Angular Momentum Distribution.- Angular Momentum Effects in Star Formation.- Evolutionary Properties of Intermediate-Mass Protostar.- Small-Scale Structure and Angular Momentum Transfer in Protostellar Environments.- Ekman Pumping in a Rotating Protostar.- Rotation in Pre-Main Sequence Stars; Properties and Evolution.- Disks Associated with Intermediate Mass Stars.- Differential Rotation of Fully Convective Pre-Main Sequence Stars.- The X-ray Emission from PMS Stars in Taurus-Auriga, and the Relationship with Other Diagnostics of Activity.- Multifrequency Monitoring of RU Lupi; Observational Results and a Model.- Polarimetry and CCD Imaging of Herbig Ae/Be Stars and Star Forming Regions.- II: Angular Momentum Evolution.- Rotational Velocities of Low Mass Stars in Young Clusters.- Rotation of Young Stars in the Orion Nebula Region.- Rotational Velocities of Stars in Open Clusters; the Time-Dependence Revisited.- Main Sequence Angular Momentum Loss in Low-Mass Stars.- The Angular Momentum Evolution of Young and Old Binary Components.- Ages of Spotted Late-Type Stars.- Rotation of Evolved Stars.- Rotational Discontinuity of Evolved Stars; What Interpretation?.- III: Consequence of Rotation.- Magnetic Activity and Rotation.- Lithium, Rotation and Age.- Rotation, Chromospheric Activity, and Lithium Abundances in G and K Dwarfs of the Pleiades.- Lithium Abundance and Rotation in Southern Chromospherically Active Stars.- Lithium Depletion Induced by Rotation in Young Stars.- Rotational Mixing and Lithium in Young Stars.- IV: Internal Rotation and Models.- Internal Solar Rotation.- Stellar Activity Belts as Potential Indicators of Internal Rotation and Angular Momentum Distribution.- Dynamics of Spot Groups and Rotation of the External Convective Layers in the Sun and Magnetically Active Stars.- Theory of Magnetic Braking of Late-Type Stars.- Pre-Main Sequence and Main Sequence Rotational Evolution; Constraints on Models Derived from Observations.- Evolutionary Models of Rotating Stars.- The Internal Rotation of the Sun; Implications on the History of its Angular Momentum.- Angular Momentum Transport, Rotational Instabilities, Magnetic Fields and Mixing.- The Spin-Down of Main Sequence Stars Based on Observed Magnetic Field Strength.- Session V: Observational Perspectives.- Observational Perspectives.- PRISMA: a Space Facility for Studying Rotation and Activity.- The Spectrum-UV Project.- Summary of the Workshop.- Panel Discussion: Initial Angular Momentum.- Panel Discussion: Dynamos and Internal Rotation.- Author Index.- Object Index.

One of the most spectacular discoveries of molecular astronomy has been the detection of maser emission. The same radiation that is generated in the laboratory only with elaborate, special equipment occurs naturally in interstellar space. This intense radiation probes the smallest structures that can be studied with radio telescopes. By a fortunate coincidence maser radiation is generated in both star forming regions and the envelopes of late-type stars. The early and late stages in the life of a star are considered to be the most interesting phases of stellar evolution. Maser emission has also been detected in external galaxies. This book provides an extensive coverage of the interstellar maser phenomenon. A precondition for maser action is departure from thermal equilibrium. The book therefore starts with a detailed coverage of the basic background concepts required for an understanding of line formation and radiative transfer. It goes on to describe the theoretical and phenomenological aspects of interstellar masers, their formation sites and the inversion mechanisms. The book will interest active researchers in astronomy and astrophysics as well as in other areas of physics. It is suitable as a textbook in a graduate course and will enable a graduate student to embark on research projects in this exciting area in particular, and molecular radio astronomy in general.

One of the most spectacular discoveries of molecular astronomy has been the detection of maser emission. The same radiation that is generated in the laboratory only with elaborate, special equipment occurs naturally in interstellar space. This intense radiation probes the smallest structures that can be studied with radio telescopes. By a fortunate coincidence maser radiation is generated in both star forming regions and the envelopes of late-type stars. The early and late stages in the life of a star are considered to be the most interesting phases of stellar evolution. Maser emission has also been detected in external galaxies. This book provides an extensive coverage of the interstellar maser phenomenon. A precondition for maser action is departure from thermal equilibrium. The book therefore starts with a detailed coverage of the basic background concepts required for an understanding of line formation and radiative transfer. It goes on to describe the theoretical and phenomenological aspects of interstellar masers, their formation sites and the inversion mechanisms. The book will interest active researchers in astronomy and astrophysics as well as in other areas of physics. It is suitable as a textbook in a graduate course and will enable a graduate student to embark on research projects in this exciting area in particular, and molecular radio astronomy in general.

1-Pre-White Dwarf Evolution and White Dwarf Cooling.- New pre-white dwarf evolutionary tracks.- Influence of the phase diagram in the cooling of white dwarfs.- PG1159 stars and the PNN-white dwarf connection.- Analysis of the soft X-ray data from the central star of NGC 7293.- Planetary Nebulae Nuclei with white dwarf spectra.- Atmospheric parameters of subluminous B stars.- White dwarf space densities and birth rates reconsidered.- A spectroscopic determination of the mass distribution of DA white dwarfs.- The age and formation of the Galaxy: clues from the white dwarf luminosity function.- Early results from the ROSAT Wide Field Camera.- The stellar component of the Hamburg Schmidt Survey.- White dwarfs in the Hamburg Schmidt Survey.- 2-Asteroseismology of White Dwarfs.- Asteroseismology of white dwarf stars with the Whole Earth Telescope.- A measurement of the evolutionary timescale of the cool white dwarf G117-B15A with WET.- On the interpretation of the dP/dt measurement in G117-B15A.- The boundaries of the ZZ Ceti instability strip.- Long term variations in ZZ Cetis: G191-16 and HL Tau 76.- Predicting the white dwarf light curves.- A wavelet analysis of the ZZ Ceti star G191 16.- An adiabatic survey for ZZ Ceti stars based on a finite element code.- A study of period change rates in post-AGB stars I. PG 1159-035.- Nonadiabatic nonradial pulsations for DAV white dwarf stars.- 3-Atmospheres and Envelopes.- NLTE Analysis of four PG1159 stars.- A search for trace amounts of hydrogen in DB stars.- Abundances of trace heavy elements in hot DA white dwarfs.- New results on radiative forces on iron in hot white dwarfs.- The effective temperature of the DBV's, and the sensitivity of DB model atmospheres to input physics.- The modified hydrostatic equilibrium equations for stratified high gravity stellar atmospheres.- The DBAQ G35-26.- LP 790-29: preliminary model atmospheres for this strongly polarized carbon white dwarf.- Some effect of the UV radiation from white dwarfs on the accretion of interstellar hydrogen.- Convection in white dwarfs: application of CM theory to helium envelope WDs.- Abundances in cool DZA and DAZ white dwarfs: new results using laboratory damping constants.- Evidence for fractionated accretion of metals on cool white dwarfs.- A new look at old friends: 40 Eri B and GD 323.- The Lyman Alpha line wing in hydrogen-rich white dwarf atmospheres.- Atmospheric parameters for DA white dwarfs in the vicinity of the ZZ Ceti instability strip.- Space Telescope observations of white dwarf stars.- 4-White Dwarfs in Binaries.- A deep spectroscopic survey of white dwarfs in common proper motion binaries.- Double degenerate common proper motion binaries.- Close binary white dwarfs.- New results on cataclysmic variable white dwarfs.- Whole Earth Telescope observations of the interacting white dwarf binary system AM CVn: first results.- IUE observations of V803 Cen in high and low states.- Whole Earth Telescope observations of PG1346+082.- On the origin of LMXRBS: the ONEMG case.