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

Degenaar, N. and Altamirano, D. and Parker, M. and Miller-Jones, J. C. A. and Miller, J. M. and Heinke, C. O. and Wijnands, R. and Ludlam, R. and Parikh, A. and Hessels, J. W. T. and Gusinskaia, N. and Deller, A. T. and Fabian, A. C. (2016) Disk reflection and a possible disk 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). pp. 4049-4058. ISSN 0035-8711. http://resolver.caltech.edu/CaltechAUTHORS:20160708-151940241

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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 L_X ≃ (2–3) × 10^(37)(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 R_(in) ≃ 5–7.5 gravitational radii (≃11–17 km). This inner disc radius suggests that the neutron star magnetic field strength is B ≲ 2 × 10^8 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 v_(out) ≃ 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 (P_(orb) ≲ 3 h) binary orbit.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/mnras/stw1593DOIArticle
https://academic.oup.com/mnras/article/461/4/4049/2608724PublisherArticle
http://arxiv.org/abs/1607.01780arXivDiscussion Paper
ORCID:
AuthorORCID
Heinke, C. O.0000-0003-3944-6109
Additional Information:© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 June 30. Received 2016 June 30; in original form 2016 May 4. Published: 04 July 2016. We are grateful to Belinda Wilkes, Fiona Harrison, Neil Gehrels and the Chandra, NuSTAR and Swift teams for carrying out these DDT observations. We thank the anonymous referee for constructive comments. ND thanks Ciro Pinto, Matt Middleton and Anne Lohfink for useful discussions. ND is supported by an NWO/Vidi grant and an EU Marie Curie Intra-European fellowship under contract no. FP-PEOPLE-2013-IEF-627148. DA acknowledges support from the Royal Society. JCAMJ is supported by an Australian Research Council (ARC) Future Fellowship (FT140101082) and an ARC Discovery Grant (DP120102393). RW and AP are supported by an NWO/TOP grant, module 1, awarded to RW. COH is supported by an NSERC Discovery Grant. ATD is supported by an NWO/Veni grant. JWTH is supported by NWO/Vidi and ERC/starting (337062) grants.
Group:NuSTAR
Subject Keywords:accretion: accretion disks – stars: individual (1RXS J180408.9–342058) – stars: neutron – stars: winds, outflows – X-rays: binaries
Record Number:CaltechAUTHORS:20160708-151940241
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160708-151940241
Official Citation: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, A. T. Deller, A. C. Fabian; 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, Volume 461, Issue 4, 1 October 2016, Pages 4049–4058, https://doi.org/10.1093/mnras/stw1593
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68937
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Jul 2016 22:42
Last Modified:13 Dec 2017 04:53

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