Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Post-merger evolution of carbon-oxygen + helium white dwarf binaries and
  the origin of R Coronae Borealis and extreme helium stars   Orbital decay by gravitational-wave radiation will cause some close-binary
white dwarfs (WDs) to merge within a Hubble time. The results from previous
hydrodynamical WD-merger simulations have been used to guide calculations of
the post-merger evolution of carbon-oxygen + helium (CO+He) WD binaries. Our
models include the formation of a hot corona in addition to a Keplerian disk.
We introduce a 'destroyeddisk' model to simulate the effect of direct disk
ingestion into the expanding envelope. These calculations indicate significant
lifetimes in the domain of the rare R Coronae Borealis (RCB) stars, before a
fast evolution through the domain of the hotter extreme helium (EHe) stars.
Surface chemistries of the resulting giants are in partial agreement with the
observed abundances of RCB and EHe stars. The production of 3He, 18O and 19F
are discussed. Evolutionary timescales combined with binary white-dwarf merger
rates from binary-star population synthesis are consistent with present-day
numbers of RCBs and EHes, provided that the majority come from relatively
recent (< 2Gyr) star formation. However, most RCBs should be produced by CO-WD
+ low-mass HeWD mergers, with the He-WD having a mass in the range 0.20-0.35
Msolar. Whilst, previously, a high He-WD mass (> 0.40 Msolar) was required to
match the carbon-rich abundances of RCB stars, the 'destroyed-disk' model
yields a high-carbon product with He-WD mass > 0.30 Msolar, in better agreement
with population synthesis results.

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The categories of this paper are: nlin
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The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph