Hydrogen-deficient central stars revisited

W.-R. Hamann, H. Todt and G. Gräfener

Universität Potsdam, Institut für Physik, Astrophysik

Previous spectral analyses of Wolf-Rayet type central stars resulted in different abundance patterns for late- and early [WC] subtypes, which could not be explained in the framework of post-AGB evolutionary scenarios with any form of a late thermal pulse. Presently we re-analyze systematically these stars, using the most recent version of our non-LTE models for expanding atmospheres which now account for line blanketing by the iron-group elements. So far we revisited the early subtypes. Although for some stars the carbon abundances are revised upwards, they are still only between 24 and 40% by mass and thus systematically lower than for late subtypes. This is inconsistent with an evolutionary sequence [WCL] --> [WCE].

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