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# Photospheric Radius Expansion and a Double-peaked Type-I X-Ray Burst from GRS 1741.9-2853

Pike, Sean N., Harrison, Fiona A., Tomsick, John A., Bachetti, Matteo, Buisson, Douglas J.K., Garcia, Javier A., Jiang, Jiachen, Ludlam, R.M. and Madsen, Kristin K. (2021) Photospheric Radius Expansion and a Double-peaked Type-I X-Ray Burst from GRS 1741.9-2853. Astrophysical Journal, 918 (1), [9].

Record type: Article

## Abstract

We present an analysis of two type-I X-ray bursts observed by NuSTAR originating from the very faint transient neutron star (NS) low-mass X-ray binary GRS 1741.9–2853 during a period of outburst in 2020 May. We show that the persistent emission can be modeled as an absorbed, Comptonized blackbody in addition to Fe Kα emission, which can be attributed to relativistic disk reflection. We measure a persistent bolometric, unabsorbed luminosity of ${L}_{\mathrm{bol}}={7.03}_{-0.05}^{+0.04}\times {10}^{36}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$, assuming a distance of 7 kpc, corresponding to an Eddington ratio of 4.5%. This persistent luminosity combined with light-curve analysis leads us to infer that the bursts were the result of pure He burning rather than mixed H/He burning. Time-resolved spectroscopy reveals that the bolometric flux of the first burst exhibits a double-peaked structure, placing the source within a small population of accreting NSs that exhibit multiple-peaked type-I X-ray bursts. We find that the second, brighter burst shows evidence for photospheric radius expansion (PRE) and that at its peak, this PRE event had an unabsorbed bolometric flux of ${F}_{\mathrm{peak}}={2.94}_{-0.26}^{+0.28}\times {10}^{-8}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}\,{{\rm{s}}}^{-1}$. This yields a new distance estimate of d = 9.0 ± 0.5 kpc, assuming that this corresponds to the Eddington limit for pure He burning on the surface of a canonical NS. Additionally, we performed a detailed timing analysis that failed to find evidence for quasi-periodic oscillations or burst oscillations, and we place an upper limit of 16% on the rms variability around 589 Hz, the frequency at which oscillations have previously been reported.

Text
Photospheric Radius Expansion and a Double-peaked Type-I X-Ray Burst from GRS 1741.9-2853 - Accepted Manuscript
Restricted to Repository staff only until 30 August 2022.
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Accepted/In Press date: 24 June 2021
Published date: 30 August 2021

## Identifiers

Local EPrints ID: 451964
URI: http://eprints.soton.ac.uk/id/eprint/451964
ISSN: 0004-637X
PURE UUID: 25f59321-dde9-4dfb-b6ee-eb8912d799f5

## Catalogue record

Date deposited: 04 Nov 2021 17:34

## Contributors

Author: Sean N. Pike
Author: Fiona A. Harrison
Author: John A. Tomsick
Author: Matteo Bachetti
Author: Douglas J.K. Buisson
Author: Javier A. Garcia
Author: Jiachen Jiang
Author: R.M. Ludlam

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