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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.
On April 28 1986 Cornelis de Jager reached the age of 65 years. On
April 30 he officially retired from the University of Utrecht where
he has held a Chair for Stellar Astrophysics, later changed into
Space Physics, since 1958. Cees de Jager, as he prefers to be
called by his friends, has had an active and successful life in
science. His interest in astronomy was raised by his father under
the clear skies of Celebes (Indonesia). He started a study in
physics and astronomy as a student of the late M. Minnaert in
Utrecht during World War II. When in 1943 the occupying forces
recruited students who did not want to sign the declaration of
loyalty for their war-efforts, Cees and three fellow students went
into hiding at the Observatory in Utrecht. During this very "quiet"
period van de Hulst developed the theory of the 21 em radiation of
neutral hydrogen and de Jager started the observations of variable
stars in the pitch dark nights of a country at war. The study of
Beta Cepheids rapid ly awoke his interest which was kept throughout
the years. In 1958 he organized an international campaign to
observe 12 Lac spectroscopically and photometrically, which was a
great success."
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 astrophysicsstudents will become
fascinated by the exciting world of the Brightest Binaries'.
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.
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 formative ideas for this symposium originated in 1978 at the
IAU Symposium No. 83 on "Mass Loss and Evolution of O-type Stars"
held at Qualicum Beach, Vancouver Island, Canada - WR stars
generally figure prominently in O-star meetings and vice versa
Following general appro val by the IAU Executive Committee the
initial ideas were cemented at a subsequent meeting, IAU Colloquium
No. 59 on "The Effects of Mass Loss on Stellar Evolution," held at
Miramare, Trieste, Italy in 1980, which was attended by the ma,
jority of the present Scientific Organising Committee and at which
meeting the outline programme for this symposium was formulated.
1981 was considered an appropriate year in which to hold a meeting
on WR stars, since the last IAU Symposium devoted to this stellar
class had been held a decade earlier, in Buenos Aires (IAU Sym
posium No. 49), and during this intervening period a wealth of new
observational material had been obtained for WR stars together with
significant advances on the theoretical front. The venue for this
sym posium was chosen from the requirement, which can be inferred
from the above, that a meeting on 'hot' stars take place in an
appropriate, sunny climate and followed upon the excellent
suggestion of Dr. C. Firmani to hold the symposium in Mexico."
The organization of this Symposium had its beginnings at the
International Astronomical Union General Assembly in Grenoble in
1976. The initial "rounding up" of the Scienti fic Organizing
Committee was begun by Drs. Snow and Swings; most of us who became
the eventual organizing committee met a few times during the
Assembly and formulated the essential outlines of the meeting.
Extensive correspondence with all the committee subsequently
established the program. The idea was to bring together both
observers and theoreticians to discuss the stellar winds and mass
loss rates and their effects on evolutions of O-type stars. On the
observational side, there are now spectroscopic data from the far
UV to the near IR regions concerning the stellar winds. There is
also information about the free-free emission in the wind from the
IR and radio portions of the spectrum. Fortunately, these different
detection methods give more or less the same mass loss rate for the
one star, s Pup" which has been observed at all wavelengths. One of
the intents of the first three sessions of this Symposium is to
outline the eXisting data on mass loss rates as it per tains to the
O-type stars."
The Proceedings of the 17th International Cosmic Ray Conference
held in Paris, July 15 to 25, 1981, appear in two sets. The Regular
Volumes, 1 to 8, contain contributed papers received at the
Secretariat by April 1st, 1981. They were issued at the opening of
the Conference. The Late Volumes, 9 to 14, contain contributed
papers received after that date, Invited and Rapporteur Talks, and
the General Index. The assiduous reader will notice several changes
with respect to the well-established traditions of the Conference.
1/ Following a recommendation of the Commission an Cosmic Rays of
IUPAP, and although an increase in the total number of papers
submitted was noticed as compared to the 16th ICRC (Kyoto, 1979),
the total number of pages has been significantly reduced, thanks to
introduction of three new rules for publication. (i) None of the
first "Preliminary" Abstracts was published. These abstracts had to
be confirmed, either by a new "Confirming Abstract" or by a Full
Paper. The Confirming Abstracts are included in the Proceedings.
(ii) The sum of the "fractional" contributions of each author
should not exceed 3 papers, and each author should not appear in
more than 10 papers. (iii) The maximum number of pages per paper
was reduced from 6 to 4. The Organizing Committee thanks all
authors who have, in their vast majority, very efficiently
cooperated by kindly complying with these new rules. The papers we
selected an the basis of the Preliminary Abstracts.
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