http://arxiv.org/abs/1711.03285
It is not known how single white dwarfs with masses less than 0.5Msolar — low-mass white dwarfs — are formed. One way in which such a white dwarf might be formed is after the merger of a helium-core white dwarf with a main-sequence star that produces a red giant branch star and fails to ignite helium. We use a stellar-evolution code to compute models of the remnants of these mergers and find a relation between the pre-merger masses and the final white dwarf mass. Combining our results with a model population, we predict that the mass distribution of single low-mass white dwarfs formed through this channel spans the range 0.37 to 0.5Msolar and peaks between 0.45 and 0.46Msolar. Helium white dwarf–main-sequence star mergers can also lead to the formation of single helium white dwarfs with masses up to 0.51Msolar. In our model the Galactic formation rate of single low-mass white dwarfs through this channel is about 8.7X10^-3yr^-1. Comparing our models with observations, we find that the majority of single low-mass white dwarfs (<0.5Msolar) are formed from helium white dwarf–main-sequence star mergers, at a rate which is about $2$ per cent of the total white dwarf formation rate.
X. Zhang, P. Hall, C. Jeffery, et. al.
Fri, 10 Nov 17
35/55
Comments: 6 pages, 7 figures, MNRAS accepted, in press
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