Title:	AstroSat and NuSTAR obser v ations of XTE J1739 −285 during the 2019–2020 outburst
Authors:	Beri, Aru Sharma, Rahul Roy, Pinaki Gaur, Vishal Altamirano, Diego Andersson, Nils Gittins, Fabian Celora, T.
Keywords:	Accretion, Accretion discs –stars: Neutron –X-ray: Binaries –X-rays: Bursts –X-rays: Individual (XTE J1739 −285)
Issue Date:	24-Mar-2023
Publisher:	Royal Astronomical Society
Citation:	Monthly Notices of the Royal Astronomical Society,2023,Vol.521, p5904
Abstract:	We report results from a study of XTE J1739 −285, a transient neutron star low mass X-ray binary observed with AstroSat and NuSTAR during its 2019–2020 outburst. We detected accretion-powered X-ray pulsations at 386 Hz during very short intervals (0.5–1 s) of X-ray flares. These flares were observed during the 2019 observation of XTE J1739 −285. During this observation, we also observed a correlation between intensity and hardness ratios, suggesting an increase in hardness with the increase in intensity. Moreo v er, a thermonuclear X-ray burst detected in our AstroSat observation during the 2020 outburst revealed the presence of coherent burst oscillations at 383 Hz during its decay phase. The frequency drift of 3 Hz during X-ray burst can be explained with r modes. Thus, making XTE J1739 −285 belong to a subset of NS-LMXBs which exhibit both nuclear- and accretion-po wered pulsations. The po wer density spectrum created using the AstroSat - LAXPC observations in 2020 showed the presence of a quasi-periodic oscillation at ∼0.83 Hz. Our X-ray spectroscopy revealed significant changes in the spectra during the 2019 and 2020 outburst. We found a broad iron line emission feature in the X-ray spectrum during the 2020 observation, while this feature was relatively narrow and has a lower equivalent width in 2019, when the source was accreting at higher rates than 2020. Hard X-ray tail was observed during the 2019 observations, indicating the presence of non-thermal component in the X-ray spectra.
Description:	Open Access
URI:	http://hdl.handle.net/2289/8203
ISSN:	0035-8711 (print) 1365-2966 (online)
Alternative Location:	https://ui.adsabs.harvard.edu/abs/2023MNRAS.521.5904B/abstract https://arxiv.org/abs/2303.13085 https://doi.org/10.1093/mnras/stad902
Copyright:	2023, The Author(s)
Appears in Collections:	Research Papers (A&A)

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