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Disc reflection and a possible disc wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9–342058

Disc reflection and a possible disc wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9–342058
Disc reflection and a possible disc wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9–342058
1RXS J180408.9–342058 is a transient neutron star low-mass X-ray binary that exhibited a bright accretion outburst in 2015. We present NuSTAR, Swift, and Chandra observations obtained around the peak brightness of this outburst. The source was in a soft X-ray spectral state and displayed an X-ray luminosity of LX ? (2–3) × 1037(D/5.8?kpc)2?erg?s?1 (0.5–10 keV). The NuSTAR data reveal a broad Fe–K emission line that we model as relativistically broadened reflection to constrain the accretion geometry. We found that the accretion disc is viewed at an inclination of i ? 27°–35° and extended close to the neutron star, down to Rin ? 5–7.5 gravitational radii (?11–17 km). This inner disc radius suggests that the neutron star magnetic field strength is B ? 2 × 108 G. We find a narrow absorption line in the Chandra/HEG data at an energy of ?7.64 keV with a significance of ?4.8?. This feature could correspond to blueshifted Fe xxvi and arise from an accretion disc wind, which would imply an outflow velocity of vout ? 0.086c (?25 800?km?s?1). However, this would be extreme for an X-ray binary and it is unclear if a disc wind should be visible at the low inclination angle that we infer from our reflection analysis. Finally, we discuss how the X-ray and optical properties of 1RXS J180408.9–342058 are consistent with a relatively small (Porb ? 3 h) binary orbit
0035-8711
4049-4058
Degenaar, N.
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Altamirano, D.
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Parker, M.
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Miller-Jones, J.C.A.
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Miller, J.M.
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Heinke, C.O.
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Wijnands, R.
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Ludlam, R.
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Parikh, A.
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Hessels, J.W.T.
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Gusinskaia, N.
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Deller, A.T.
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Fabian, A.C.
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Degenaar, N.
54149051-d74e-4e43-a7cd-501ec4023511
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Parker, M.
f35e48ca-14b4-4c90-b172-f24c84861250
Miller-Jones, J.C.A.
de372f09-251a-4a6c-93d9-a30ec089473f
Miller, J.M.
078305f0-03c7-4982-95ff-a92bc2f75b54
Heinke, C.O.
81e86af6-563d-4efc-ba4f-8e2902b2c9da
Wijnands, R.
382893ee-0e03-45e3-9321-db8b9fc74914
Ludlam, R.
14eb530f-6cbb-4886-8f0f-ef7f1bc34c32
Parikh, A.
827ba362-a0c9-4838-8bc4-01a1f7bf0500
Hessels, J.W.T.
4d281d39-14f4-4ca7-a6f9-05bdc0eb7b9f
Gusinskaia, N.
93c92e0c-f8c6-4c9d-92c5-aee00fe6eb8c
Deller, A.T.
d9eab233-8cf7-4f14-a590-e02da059b13d
Fabian, A.C.
0c353376-f159-4129-b03e-d3993c0c5406

Degenaar, N., Altamirano, D., Parker, M., Miller-Jones, J.C.A., Miller, J.M., Heinke, C.O., Wijnands, R., Ludlam, R., Parikh, A., Hessels, J.W.T., Gusinskaia, N., Deller, A.T. and Fabian, A.C. (2016) Disc reflection and a possible disc wind during a soft X-ray state in the neutron star low-mass X-ray binary 1RXS J180408.9–342058. Monthly Notices of the Royal Astronomical Society, 461 (4), 4049-4058. (doi:10.1093/mnras/stw1593).

Record type: Article

Abstract

1RXS J180408.9–342058 is a transient neutron star low-mass X-ray binary that exhibited a bright accretion outburst in 2015. We present NuSTAR, Swift, and Chandra observations obtained around the peak brightness of this outburst. The source was in a soft X-ray spectral state and displayed an X-ray luminosity of LX ? (2–3) × 1037(D/5.8?kpc)2?erg?s?1 (0.5–10 keV). The NuSTAR data reveal a broad Fe–K emission line that we model as relativistically broadened reflection to constrain the accretion geometry. We found that the accretion disc is viewed at an inclination of i ? 27°–35° and extended close to the neutron star, down to Rin ? 5–7.5 gravitational radii (?11–17 km). This inner disc radius suggests that the neutron star magnetic field strength is B ? 2 × 108 G. We find a narrow absorption line in the Chandra/HEG data at an energy of ?7.64 keV with a significance of ?4.8?. This feature could correspond to blueshifted Fe xxvi and arise from an accretion disc wind, which would imply an outflow velocity of vout ? 0.086c (?25 800?km?s?1). However, this would be extreme for an X-ray binary and it is unclear if a disc wind should be visible at the low inclination angle that we infer from our reflection analysis. Finally, we discuss how the X-ray and optical properties of 1RXS J180408.9–342058 are consistent with a relatively small (Porb ? 3 h) binary orbit

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Accepted/In Press date: 30 June 2016
e-pub ahead of print date: 4 July 2016
Published date: 1 October 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 401431
URI: http://eprints.soton.ac.uk/id/eprint/401431
ISSN: 0035-8711
PURE UUID: cf0fb99c-8aff-4a67-a061-ba7e2e5f6bea
ORCID for D. Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

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Date deposited: 13 Oct 2016 13:40
Last modified: 17 Dec 2019 01:35

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