Revised spectral analyses of Galactic WC stars
Institut für Physik und Astronomie, Universität Potsdam, Germany
Institut für Physik und Astronomie, Universität Potsdam, Germany
Institut für Physik und Astronomie, Universität Potsdam, Germany
Abstract
A grid of models for Wolf-Rayet stars of the carbon sequence (WC) has been established with the Potsdam Wolf-Rayet (PoWR) model atmosphere code. In contrast to earlier versions, clumping and iron line blanketing are now taken into account. The spectra of more than 50 Galactic WC stars with subtypes ranging from WC4 to WC9 have been analyzed by finding the best-fitting model from the grid. While the spectra of Wolf-Rayet stars of the nitrogen sequence (WN) can be nicely reproduced by a PoWR model fit, the WC spectra show a couple of features that cannot be consistently reproduced by a single model. Nevertheless, the models can be applied for their spectral analysis. The obtained parameters clearly reflect the sequence of WC spectral subtypes. From the positions of the WC stars in the Hertzsprung-Russell diagram we conclude that WC stars descend from stars with initial masses between 20 Mo and 40 Mo while stars with higher masses do not reach the WC stage.