Evolution models of helium white dwarf--main sequence star merger remnants
Abstract
It is predicted that orbital decay by gravitational-wave radiation and tidal interaction will cause some close-binary stars to merge within a Hubble time. The merger of a helium-core white dwarf with a main-sequence star can produce a red giant branch star that has a low-mass hydrogen envelope when helium is ignited and thus become a hot subdwarf. Because detailed calculations have not been made, we compute post-merger models with a stellar evolution code. We find the evolutionary paths available to merger remnants and find the pre-merger conditions that lead to the formation of hot subdwarfs. We find that some such mergers result in the formation of stars with intermediate helium-rich surfaces. These stars later develop helium-poor surfaces owing to diffusion. Combining our results with a model population and comparing to observed stars, we find that some observed intermediate helium-rich hot subdwarfs can be explained as the remnants of the mergers of helium-core white dwarfs with low-mass main-sequence stars.
Cite
@article{arxiv.1701.02437,
title = {Evolution models of helium white dwarf--main sequence star merger remnants},
author = {Xianfei Zhang and Philip D. Hall and C. Simon Jeffery and Shaolan Bi},
journal= {arXiv preprint arXiv:1701.02437},
year = {2017}
}
Comments
10 pages, 13 figures, accepted for publication in ApJ