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Mass transfer in white dwarf-neutron star binaries

Bobrick, Alexey LU ; Davies, Melvyn B. LU and Church, Ross P. LU (2017) In Monthly Notices of the Royal Astronomical Society 467(3). p.3556-3575
Abstract
We perform hydrodynamic simulations of mass transfer in binaries that contain a white dwarf and a neutron star (WD-NS binaries), and measure the specific angular momentum of material lost from the binary in disc winds. By incorporating our results within a long-term evolution model, we measure the long-term stability of mass transfer in these binaries. We find that only binaries containing helium white dwarfs (WDs) with masses less than a critical mass of M-WD, (crit) = 0.2 M-circle dot undergo stable mass transfer and evolve into ultracompact X-ray binaries. Systems with higher mass WDs experience unstable mass transfer, which leads to tidal disruption of the WD. Our low critical mass compared to the standard jet-only model of mass-loss... (More)
We perform hydrodynamic simulations of mass transfer in binaries that contain a white dwarf and a neutron star (WD-NS binaries), and measure the specific angular momentum of material lost from the binary in disc winds. By incorporating our results within a long-term evolution model, we measure the long-term stability of mass transfer in these binaries. We find that only binaries containing helium white dwarfs (WDs) with masses less than a critical mass of M-WD, (crit) = 0.2 M-circle dot undergo stable mass transfer and evolve into ultracompact X-ray binaries. Systems with higher mass WDs experience unstable mass transfer, which leads to tidal disruption of the WD. Our low critical mass compared to the standard jet-only model of mass-loss arises from the efficient removal of angular momentum in the mechanical disc winds, which develop at highly super-Eddington mass-transfer rates. We find that the eccentricities expected for WD-NS binaries when they come into contact do not affect the loss of angular momentum, and can only affect the long-term evolution if they change on shorter time-scales than the mass-transfer rate. Our results are broadly consistent with the observed numbers of both ultracompact X-ray binaries and radio pulsars with WD companions. The observed calcium-rich gap transients are consistent with the merger rate of unstable systems with higher mass WDs. (Less)
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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
hydrodynamics, methods: numerical, binaries: close, stars: neutron, white dwarfs
in
Monthly Notices of the Royal Astronomical Society
volume
467
issue
3
pages
20 pages
publisher
Oxford University Press
external identifiers
  • scopus:85039170078
ISSN
0035-8711
DOI
10.1093/mnras/stx312
language
English
LU publication?
yes
id
9f4d026e-425e-41e7-8dfa-8f8b2abfccff
date added to LUP
2018-09-27 19:58:52
date last changed
2020-12-29 01:18:45
@article{9f4d026e-425e-41e7-8dfa-8f8b2abfccff,
  abstract     = {We perform hydrodynamic simulations of mass transfer in binaries that contain a white dwarf and a neutron star (WD-NS binaries), and measure the specific angular momentum of material lost from the binary in disc winds. By incorporating our results within a long-term evolution model, we measure the long-term stability of mass transfer in these binaries. We find that only binaries containing helium white dwarfs (WDs) with masses less than a critical mass of M-WD, (crit) = 0.2 M-circle dot undergo stable mass transfer and evolve into ultracompact X-ray binaries. Systems with higher mass WDs experience unstable mass transfer, which leads to tidal disruption of the WD. Our low critical mass compared to the standard jet-only model of mass-loss arises from the efficient removal of angular momentum in the mechanical disc winds, which develop at highly super-Eddington mass-transfer rates. We find that the eccentricities expected for WD-NS binaries when they come into contact do not affect the loss of angular momentum, and can only affect the long-term evolution if they change on shorter time-scales than the mass-transfer rate. Our results are broadly consistent with the observed numbers of both ultracompact X-ray binaries and radio pulsars with WD companions. The observed calcium-rich gap transients are consistent with the merger rate of unstable systems with higher mass WDs.},
  author       = {Bobrick, Alexey and Davies, Melvyn B. and Church, Ross P.},
  issn         = {0035-8711},
  language     = {eng},
  month        = {06},
  number       = {3},
  pages        = {3556--3575},
  publisher    = {Oxford University Press},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Mass transfer in white dwarf-neutron star binaries},
  url          = {http://dx.doi.org/10.1093/mnras/stx312},
  doi          = {10.1093/mnras/stx312},
  volume       = {467},
  year         = {2017},
}