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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

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posted on 2024-08-06, 10:31 authored by N. Degenaar, D. Altamirano, M. Parker, J. C A Miller-Jones, J. M. Miller, C. O. Heinke, R. Wijnands, R. Ludlam, A. Parikh, J. W T Hessels, N. Gusinskaia, Adam DellerAdam Deller, A. C. Fabian
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 ≃4.8σ. 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.

Funding

Feeding the faintest black holes: the nature of low-luminosity accretion

Australian Research Council

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The origin and nature of relativistic jets in X-ray binaries

Australian Research Council

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ISSN

1365-2966

Journal title

Monthly Notices of the Royal Astronomical Society

Volume

461

Issue

4

Pagination

9 pp

Publisher

Oxford University Press (OUP)

Copyright statement

This article has been accepted for publication in the Monthly Notices of the Royal Astronomical Society ©: 2016 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Language

eng

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