# 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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Publication Date: 2016-10-01

Journal Title: Monthly Notices of the Royal Astronomical Society

Publisher: Oxford University Press

Volume: 461

Issue: 4

Pages: 4049-4058

Language: English

Type: Article

This Version: VoR

Citation: Degenaar, N. D., Altamirano, D., Parker, M. A., Miller-Jones, J., Miller, J., Heinke, C., Wijnands, R., et al. (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. https://doi.org/10.1093/mnras/stw1593

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 $\textit{NuSTAR}$, $\textit{Swift}$, and $\textit{Chandra}$ 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 $L_\text{X}$ $\simeq$ (2–3) × 10$^{37}$($D$/5.8 kpc)$^2$ erg s$^{−1}$ (0.5–10 keV). The $\textit{NuSTAR}$ 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 $i$ $\simeq$ 27$^{\circ}$–35$^{\circ}$ and extended close to the neutron star, down to $R_\text{in}$ $\simeq$ 5–7.5 gravitational radii ($\simeq$11–17 km). This inner disc radius suggests that the neutron star magnetic field strength is $B$ $\lesssim$ 2 × 10$^8$ G. We find a narrow absorption line in the $\textit{Chandra}$/HEG data at an energy of $\simeq$7.64 keV with a significance of $\simeq$4.8$\sigma$. This feature could correspond to blueshifted Fe $\small \text{XXVI}$ and arise from an accretion disc wind, which would imply an outflow velocity of $v_\text{out}$ $\simeq$0.086$c$ ($\simeq$25 800 km s$^{−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_\text{orb}$ $\lesssim$ 3 h) binary orbit.

Keywords: accretion, accretion discs, stars: individual: 1RXS J180408.9–342058, stars: neutron, stars: winds, outflows, X-rays: binaries

Sponsorship: 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.

Embargo Lift Date: 2100-01-01

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External DOI: https://doi.org/10.1093/mnras/stw1593

This record's URL: https://www.repository.cam.ac.uk/handle/1810/263056

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Autor: Degenaar, Nathalie DeborahAltamirano, D Parker, Michael AndrewMiller-Jones, JCAMiller, JMHeinke, COWijnands, RLudlam, RParikh, AHe

Fuente: https://www.repository.cam.ac.uk/handle/1810/263056

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