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Thermal and radiation driving can produce observable disk winds in hard-state X-ray binaries

Thermal and radiation driving can produce observable disk winds in hard-state X-ray binaries
Thermal and radiation driving can produce observable disk winds in hard-state X-ray binaries
X-ray signatures of outflowing gas have been detected in several accreting black-hole binaries, always in the soft state. A key question raised by these observations is whether these winds might also exist in the hard state. Here, we carry out the first full-frequency radiation hydrodynamic simulations of luminous ($\rm{L = 0.5 \, L_{\mathrm{Edd}}}$) black-hole X-ray binary systems in both the hard and the soft state, with realistic spectral energy distributions (SEDs). Our simulations are designed to describe X-ray transients near the peak of their outburst, just before and after the hard-to-soft state transition. At these luminosities, it is essential to include radiation driving, and we include not only electron scattering, but also photoelectric and line interactions. We find powerful outflows with $\rm{\dot{M}_{wind} \simeq 2 \,\dot{M}_{acc}}$ are driven by thermal and radiation pressure in both hard and soft states. The hard-state wind is significantly faster and carries approximately 20 times as much kinetic energy as the soft-state wind. However, in the hard state the wind is more ionized, and so weaker X-ray absorption lines are seen over a narrower range of viewing angles. Nevertheless, for inclinations $\gtrsim 80^{\circ}$, blue-shifted wind-formed Fe XXV and Fe XXVI features should be observable even in the hard state. Given that the data required to detect these lines currently exist for only a single system in a {\em luminous} hard state -- the peculiar GRS~1915+105 -- we urge the acquisition of new observations to test this prediction. The new generation of X-ray spectrometers should be able to resolve the velocity structure.
astro-ph.HE, astro-ph.IM, astro-ph.SR
0035-8711
5271-5279
Higginbottom, Nick
99609bfd-0a53-4110-b099-6b23fbc1044e
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Sim, Stuart A.
67bb8102-b981-4e2e-9617-8c7806ef1329
Long, Knox S.
2195d0ac-518d-4738-8e89-3e8e7a035a6c
Matthews, James H.
8aa37525-32b9-460c-bb83-01c89269ac31
Hewitt, Henrietta A.
c4ab711c-bb1c-449f-82c4-51eb625bfd44
Parkinson, Edward J.
c1b87057-e577-499a-a3e6-7b31b075d3dc
Mangham, Sam W.
1dcf004d-4b2a-4e9f-9f7a-ad9b3d77675b
Higginbottom, Nick
99609bfd-0a53-4110-b099-6b23fbc1044e
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Sim, Stuart A.
67bb8102-b981-4e2e-9617-8c7806ef1329
Long, Knox S.
2195d0ac-518d-4738-8e89-3e8e7a035a6c
Matthews, James H.
8aa37525-32b9-460c-bb83-01c89269ac31
Hewitt, Henrietta A.
c4ab711c-bb1c-449f-82c4-51eb625bfd44
Parkinson, Edward J.
c1b87057-e577-499a-a3e6-7b31b075d3dc
Mangham, Sam W.
1dcf004d-4b2a-4e9f-9f7a-ad9b3d77675b

Higginbottom, Nick, Knigge, Christian, Sim, Stuart A., Long, Knox S., Matthews, James H., Hewitt, Henrietta A., Parkinson, Edward J. and Mangham, Sam W. (2020) Thermal and radiation driving can produce observable disk winds in hard-state X-ray binaries. Monthly Notices of the Royal Astronomical Society, 492 (4), 5271-5279. (doi:10.1093/mnras/staa209).

Record type: Article

Abstract

X-ray signatures of outflowing gas have been detected in several accreting black-hole binaries, always in the soft state. A key question raised by these observations is whether these winds might also exist in the hard state. Here, we carry out the first full-frequency radiation hydrodynamic simulations of luminous ($\rm{L = 0.5 \, L_{\mathrm{Edd}}}$) black-hole X-ray binary systems in both the hard and the soft state, with realistic spectral energy distributions (SEDs). Our simulations are designed to describe X-ray transients near the peak of their outburst, just before and after the hard-to-soft state transition. At these luminosities, it is essential to include radiation driving, and we include not only electron scattering, but also photoelectric and line interactions. We find powerful outflows with $\rm{\dot{M}_{wind} \simeq 2 \,\dot{M}_{acc}}$ are driven by thermal and radiation pressure in both hard and soft states. The hard-state wind is significantly faster and carries approximately 20 times as much kinetic energy as the soft-state wind. However, in the hard state the wind is more ionized, and so weaker X-ray absorption lines are seen over a narrower range of viewing angles. Nevertheless, for inclinations $\gtrsim 80^{\circ}$, blue-shifted wind-formed Fe XXV and Fe XXVI features should be observable even in the hard state. Given that the data required to detect these lines currently exist for only a single system in a {\em luminous} hard state -- the peculiar GRS~1915+105 -- we urge the acquisition of new observations to test this prediction. The new generation of X-ray spectrometers should be able to resolve the velocity structure.

Text
2001.08547v2 - Accepted Manuscript
Available under License Other.
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More information

Accepted/In Press date: 20 January 2020
e-pub ahead of print date: 25 January 2020
Published date: March 2020
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2020 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: astro-ph.HE, astro-ph.IM, astro-ph.SR

Identifiers

Local EPrints ID: 437918
URI: http://eprints.soton.ac.uk/id/eprint/437918
ISSN: 0035-8711
PURE UUID: 2a2b40cf-aff1-422a-a5b9-765c25a824a5

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Date deposited: 24 Feb 2020 17:30
Last modified: 06 Oct 2020 22:42

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