C. de Loore

D. Vanbeveren

W. van Rensbergen

Massive stars are distributed all over the upper part of the Hertzsprung-Russell diagram according to their subsequent phases of stellar evolution from main sequence to supernova. Massive stars may either be single or they may be a component of a close binary. The observed single star/binary frequency is known only in a small part of the Galaxy. Whether this holds for the whole galaxy or for the whole cosmos is questionable and needs many more high quality observations. Massive star evolution depends critically on mass loss by stellar wind and this stellar wind mass loss may change dramatically when stars evolve from one phase to another. We start the book with a critical discussion of observations of the different types of massive stars, observations that are of fundamental importance in relation to stellar evolution, with special emphasis on mass loss by stellar wind. We update our knowledge of the physics that models the structure and evolution of massive single stars and we present new calculations. The conclusions resulting from a comparison between these calculations and observations are then used to study the evolution of massive binaries. This book provides our current knowledge of a great variety of massive binaries, and hence of a great variety of evolutionary phases. A large number of case studies illustrates the existence of these phases. Finally, we present the results of massive star population number synthesis, including the effect of binaries. The results indicate that neglecting them leads to a conclusion which may be far from reality. This book is written for researchers in massive star evolution. We hope that, after reading this book, university-level astrophysics students will become fascinated by the exciting world of the `Brightest Binaries'.

The Brightest Binaries

Dany Vanbeveren

The evolution of galaxies is governed mainly by the evolution of massive stars whereas the evolution of a massive star depends primarily on its mass, chemical composition and on whether or not the star is a Single object or a binary component. To study the evolution of galaxies, it is therefore essential to know how stellar masses are distributed at birth, how many stars are formed in binaries, and what the mass ratio and orbital period distribution of binaries look like. Massive stars are intrinsically the brightest stars, so that it may be possible to discover their properties in distant groups prOvided that large telescopes can be used for basic stellar observations. However, until now the observations of massive stars have been reasonably complete only for a small region of our own Galaxy (~ 3 kpc from the Sun). One hopes that the conclusions resulting from these observations hold for the whole Galaxy, for the whole cosmos. With 'The Brightest Stars' of De Jager (1980) in mind, the present monograph is an addendum and an update in which we discuss the observations of 'The Brightest Binaries' in the framework of stellar evolution. A small or intermediate mass star close to the Sun may look brighter than a massive one far away. However, within volume limited star samples, the massive stars are on average also the brightest ones. In the present monograph (similarly as in the work of De Jager), bright means massive. The book consists of four main chapters.

Massive stars occupy an exceptional place in general astrophysics. They trigger many if not all of the important processes in galactic evolution whereas due to their intrinsic brightness, they offer the (only until now) possibility to study the stellar content and stellar behaviour in distant galaxies. The last, say, 25 years, massive stars have been the subject of numerous meetings discussing the influence of massive stars on population synthesis, the number distribution of different types of massive stars, the LBV phenomenon, WR stars, X-ray binaries, stellar winds in massive stars, chemical pecularities in massive stars, supernova explosions of massive stars and the important SN1987A event, the influence of massive stars and chemical evolution of galaxies. It is clear that without a theory of stellar evolution, the study of these topics loses a lot of its significance. Massive star evolution therefore got a chance in these meetings, but rarely as a prime subject. The state of the art, the physical processes and the uncertainties in stellar evolution were barely touched. Even more, the influence of close binaries in all these massive star meetings slowly disappeared the last, say, 13 years without any scientific justification, although a significant fraction of stars occurs in close binaries with periods small enough so that both components will interact during their evolution. Denying the binaries or not discussing their influence on results and conclusions, makes the latter very uncertain or even completely unreliable.

W. van Rensbergen

Books

Your next favorite book is out there