July 11-15, 2011
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Stellar Parameters of the Galactic WC stars

Andreas Sander (Universitšt Potsdam)

Wolf-Rainer Hamann, Universitšt Potsdam

Since the last bigger sample of Galactic WC stars had been analyzed in the middle of the 1990s, significant improvements have been achieved in the simulation of stellar-wind spectra. We have (partly re-)analyzed all available Galactic WC stars with the current generation of stellar atmosphere models computed with the Potsdam Wolf-Rayet (PoWR) code. In contrast to previous results, the obtained stellar parameters now show a close correlation with the WC subtype. The stellar temperatures form a sequence from 45kK (WC9 subtype) to about 120kK (WC4).

For those stars with known distance, we also derived luminosities using flux-calibrated spectra and photometry. We established an empirical mass loss-luminosity relation and obtained the positions of the Galatic WC stars in the HR diagram. We conclude that the Galactic WC stars evolved from initial masses in the range between 20 and 45 solar masses, likely after having passed through a red supergiant phase and the WNE stage. In combination with our previous results from WN analyses, the empirical HRD indicates that stars with initial masses above 60 Msun generally do not reach the WC stage, but keep some of their hydrogen envelope till they explode as a supernova while appearing as a WNL star or LBV.

Mode of presentation: poster