Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/ftp/stsci/library/abstracts/1089.abs Дата изменения: Fri Oct 25 22:26:23 1996 Дата индексирования: Sun Dec 23 00:14:43 2007 Кодировка: Поисковые слова: внешние планеты

\documentstyle{preprint}

\begin{document}

\title{MASSIVE STAR EVOLUTION IN DIFFERENT ENVIRONMENTS\/\thanks{Invited
review to appear in ``Active Galactic Nuclei,
Dense Stellar Systems, and their Environments,'' Eds.\ S.~A.\ Lamb,
J.~J.\ Perry, ASP Conf.~Series, 1996}}

\author{Daniel Schaerer\/\thanks{Also Geneva Observatory, CH-1290
Sauverny, Switzerland}\\
\\
Space Telescope Science Institute\\
\\
3700 San Martin Drive\\
\\
Baltimore, MD 21218\\
\\
(schaerer@stsci.edu)}

\pub{{\em the proceedings of the symposium on}\\
~\\
AGN, Dense Stellar Systems, and their Environments\\
~\\
{\em held January 1996 in Poona, India}}

\maketitle

\begin{abstract}
We review the properties of massive star evolution in different
environments, where the major environmental factor is metallicity.
Comparisons between evolutionary models and observations
of massive OB, WR stars and related objects are presented.
We also review several observations asking for future improvements of
stellar models and theoretical developments in this respect.
We summarize evolutionary scenarios for the most massive stars and
try to clarify recent questions regarding their evolutionary status
as core-H or core-He burning objects.

Another environmental effect, which might affect stellar evolution
is a cluster environment with a high stellar density.
As test cases of massive star evolution in dense clusters
we summarize recent work on the densest known resolved young
clusters: R136, NGC 3603, and the Galactic Center (GC) star cluster.
For the latter we present new comparisons between stellar parameters
of GC emission line stars derived by Najarro \etal (1994), Najarro (1995),
and Krabbe \etal (1995) and appropriate evolutionary models.
From their parameters we argue that most of these stars can be regarded
as WNL stars, and do hence not necessarily represent a peculiar class.
We suggest that some apparent differences with well known WR stars
can be understood in terms of their core burning stage and/or
other changes due to a high metallicity. Based on our present knowledge
we conclude that in young clusters with central stellar densities up to
$\rho_c \sim 10^{5-6} \, \msun {\rm pc}^{-3}$
no compelling evidence for a secondary effect influencing the evolution
of massive stars has yet been found.
\end{abstract}

\end{document}