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Paper: Carbon in Hot DB White Dwarfs: A New Challenge for the Theory of the Spectral Evolution of White Dwarfs
Volume: 334, 14th European Workshop on White Dwarfs
Page: 49
Authors: Fontaine, G.; Brassard, P.
Abstract: We present a model to account for the presence of traces of carbon in hot (~20,000 K to ~30,000 K) DB white dwarfs. Recent observations have revealed that, as a class, these stars appear to be polluted by traces of carbon and, interestingly, there appears to be no other significant pollutant. Contrary to cooler DB stars, they do not show signs of accretion, and we suggest instead that the carbon observed in their photospheres is primordial and that its presence is most likely due to a mechanism that slows down its downward diffusion. Such a mechanism could be a residual wind and we further investigate that possibility here. Within that framework, we suggest that a transition might exist along the DB cooling track around Teff ~ 20,000 K where dying winds are replaced by accretion.
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