On the Formation of Hot DQ White Dwarfs

ALTHAUS, L. G.; GARCÍA-BERRO, E.; CÓRSICO, A. H.; MILLER BERTOLAMI, M. M.; ROMERO, A. D.

The Astrophysical Journal Letters

IOP Publishing

Lugar: Bristol; Año: 2009 vol. 693 p. 23 - 26

2041-8205

We present the first full evolutionary calculations aimed at exploring the origin of hot DQ white dwarfs.These calculations consistently cover the whole evolution from the born-again stage to the white dwarfcooling track. Our calculations provide strong support for the diffusive/convective mixing picture for theformation of hot DQs. We find that the hot DQ stage is a short-lived stage and that the range of effectivetemperatures where hot DQ stars are found can be accounted for by different masses of residual heliumand/or different initial stellar masses. In the frame of this scenario, a correlation between the effectivetemperature and the surface carbon abundance in DQs should be expected, with the largest carbon abundancesexpected in the hottest DQs. From our calculations, we suggest that most of the hot DQs could be the coolerdescendants of some PG 1159 stars characterized by He-rich envelopes markedly smaller than those predictedby the standard theory of stellar evolution. At least for one hot DQ, the high-gravity white dwarf SDSSJ142625.70+575218.4, an evolutionary link between this star and the massive PG 1159 star H1504+65, is plausible.