Non-LTE metal abundances in V652 Her and HD144941
N. Przybilla, M. F. Nieva, U. Heber, C. S. Jeffery
Abstract
Two evolutionary scenarios are proposed for the formation of extreme helium stars: a post-AGB star suffering from a late thermal pulse, or the merger of two white dwarfs. An identification of the evolutionary channel for individual objects has to rely on surface abundances. We present preliminary results from a non-LTE analysis of CNO, Mg and S for two unique objects, V652 Her and HD144941. Non-LTE abundance corrections for these elements range from negligible values to ~0.7 dex. Non-LTE effects typically lead to systematic shifts in the abundances relative to LTE and reduce the uncertainties.
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