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The luminosity dependence of thermally-driven disc winds in low-mass X-ray binaries

The luminosity dependence of thermally-driven disc winds in low-mass X-ray binaries
The luminosity dependence of thermally-driven disc winds in low-mass X-ray binaries
We have carried out radiation-hydrodynamic simulations of thermally-driven accretion disc winds in low-mass X-ray binaries. Our main goal is to study the luminosity dependence of these outflows and compare with observations. The simulations span the range 0.04 ≤ Lacc/LEdd ≤ 1.0 and therefore cover most of the parameter space in which disc winds have been observed. Using a detailed Monte Carlo treatment of ionization and radiative transfer, we confirm two key results found in earlier simulations that were carried out in the optically thin limit: (i) the wind velocity -- and hence the maximum blueshift seen in wind-formed absorption lines -- increases with luminosity; (ii) the large-scale wind geometry is quasi-spherical, but observable absorption features are preferentially produced along high-column equatorial sightlines. In addition, we find that (iii) the wind efficiency always remains approximately constant at Mwind/Macc ≃ 2, a behaviour that is consistent with observations. We also present synthetic Fe XXV and Fe XXVI absorption line profiles for our simulated disc winds in order to illustrate the observational implications of our results.
astro-ph.HE, astro-ph.IM
0035-8711
4635-4644
Higginbottom, Nick
99609bfd-0a53-4110-b099-6b23fbc1044e
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Long, Knox S.
2195d0ac-518d-4738-8e89-3e8e7a035a6c
Matthews, James H.
8aa37525-32b9-460c-bb83-01c89269ac31
Parkinson, Edward J.
c1b87057-e577-499a-a3e6-7b31b075d3dc
Higginbottom, Nick
99609bfd-0a53-4110-b099-6b23fbc1044e
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Long, Knox S.
2195d0ac-518d-4738-8e89-3e8e7a035a6c
Matthews, James H.
8aa37525-32b9-460c-bb83-01c89269ac31
Parkinson, Edward J.
c1b87057-e577-499a-a3e6-7b31b075d3dc

Higginbottom, Nick, Knigge, Christian, Long, Knox S., Matthews, James H. and Parkinson, Edward J. (2019) The luminosity dependence of thermally-driven disc winds in low-mass X-ray binaries. Monthly Notices of the Royal Astronomical Society, 484 (4), 4635-4644. (doi:10.1093/mnras/stz310).

Record type: Article

Abstract

We have carried out radiation-hydrodynamic simulations of thermally-driven accretion disc winds in low-mass X-ray binaries. Our main goal is to study the luminosity dependence of these outflows and compare with observations. The simulations span the range 0.04 ≤ Lacc/LEdd ≤ 1.0 and therefore cover most of the parameter space in which disc winds have been observed. Using a detailed Monte Carlo treatment of ionization and radiative transfer, we confirm two key results found in earlier simulations that were carried out in the optically thin limit: (i) the wind velocity -- and hence the maximum blueshift seen in wind-formed absorption lines -- increases with luminosity; (ii) the large-scale wind geometry is quasi-spherical, but observable absorption features are preferentially produced along high-column equatorial sightlines. In addition, we find that (iii) the wind efficiency always remains approximately constant at Mwind/Macc ≃ 2, a behaviour that is consistent with observations. We also present synthetic Fe XXV and Fe XXVI absorption line profiles for our simulated disc winds in order to illustrate the observational implications of our results.

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1901.09684v1 - Accepted Manuscript
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Accepted/In Press date: 28 January 2019
e-pub ahead of print date: 1 February 2019
Published date: April 2019
Keywords: astro-ph.HE, astro-ph.IM

Identifiers

Local EPrints ID: 428283
URI: https://eprints.soton.ac.uk/id/eprint/428283
ISSN: 0035-8711
PURE UUID: be46a2f6-d5db-43f5-ab17-a93437aec40d

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Date deposited: 20 Feb 2019 17:30
Last modified: 19 Jul 2019 16:42

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