Abstract

WC stars and their role in the life cycle of massive stars

Wolf-Rainer Hamann (Universität Potsdam, Germany)

Andreas Sander, Universität Potsdam, Germany

The spectral analysis of Wolf-Rayet stars requires the detailed modeling of expanding stellar atmospheres in non-LTE. The Galactic WN stars have been comprehensively analyzed with such models already some years ago. With a similarly comprehensive study, we now analyzed the Galactic WC stars, using the the Potsdam Wolf-Rayet (PoWR) model atmosphere code.Stellar and atmospheric parameters have been derived for more than 50 Galactic WC and two WO stars, covering almost the whole Galactic WC population as far as the stars are single, and un-obscured in the visual. In contrast to previous studies, we find a close correlation between the spectral subtype and the stellar parameters. From comparing the empirical WC positions in the Hertzsprung-Russell diagram with evolutionary models, and from supernova statistics, we conclude that WC stars have evolved from initial masses between 20 and 45 M_sun.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 solar masses.