Hydrogen-deficient central stars revisited
W.-R. Hamann, H. Todt and G. Gräfener
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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