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arXiv · 1904.00914

Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-XRT

Aru Beri·D. Altamirano·R. Wijnands·N. Degenaar·A. S. Parikh·K. Yamaoka
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Abstract

MAXI J1957+032 is a transient Low-mass X-ray binary (LMXB) that underwent four short outbursts in 1.5 years since its discovery in 2015. The nature of the compact object in MAXI J1957+032 is not clear, but it was proposed to be a neutron star based on the short-duration of its outbursts. Here, we report the results obtained after performing spectral analysis using data obtained with the X-ray telescope aboard the Neil Gehrels Swift satellite. When describing the spectrum with an absorbed power law, we found that the spectra softens (the power-law index increases from $\sim$ 1.8 to 2.5) as the luminosity decreases. Near the end of its outbursts the observed value of power-law index ($Γ$) is $\sim$ 2.5. To identify the nature of the compact object in this system, we used $Γ$ as a tracer of the spectral evolution with luminosity. We found that for the distance of 4 kpc, our results suggest that the source harbours a neutron star.

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Aru Beri, D. Altamirano, R. Wijnands, N. Degenaar, A. S. Parikh, K. Yamaoka. 2019-04-01. Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-XRT. https://doi.org/10.1093/mnras%2Fstz938

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