Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Galactic WC stars: Stellar parameters from spectral analyses
  indicate a new evolutionary sequence   [Abridged] [...] AIMS: We aim to establish the stellar parameters and
mass-loss rates of the Galactic WC stars. These data provide the empirical
basis of studies of (i) the role of WC stars in the evolution of massive stars,
(ii) the wind-driving mechanisms, and (iii) the feedback of WC stars as input
to models of the chemical and dynamical evolution of galaxies. Methods: We
analyze the nearly complete sample of un-obscured Galactic WC stars, using
optical spectra as well as ultraviolet spectra when available. The observations
are fitted with theoretical spectra, using the Potsdam Wolf-Rayet (PoWR) model
atmosphere code. A large grid of line-blanked models has been established for
the range of WC subtypes WC4 - WC8, and smaller grids for the WC9 parameter
domain. Both WO stars and WN/WC transit types are also analyzed using special
models. Results: Stellar and atmospheric parameters are derived for more than
50 GalacticWC and two WO stars, covering almost the whole GalacticWC population
as far as the stars are single, and un-obscured in the visual. In the
Hertzsprung-Russell diagram, theWC stars reside between the hydrogen and the
helium zero-age main sequences, having luminosities L from 10^4.9 to 10^5.6
Lsun. The mass-loss rates scale very tightly with L^0.8. The two WO stars in
our sample turn out to be outstandingly hot (\approx200 kK) and do not fit into
the WC scheme. Conclusions: By comparing the empirical WC positions in the
Hertzsprung-Russell diagram with evolutionary models, and from recent supernova
statistics, we conclude that WC stars have evolved from initial masses between
20 solar masses and 45 Msun. In contrast to previous assumptions, it seems that
WC stars in general do not descend from the most massive stars. Only the WO
stars might stem from progenitors that have been initially more massive than 45
Msun.

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The categories of this paper are: econ
4
The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys