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

Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-XRT
Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-XRT
MAXI J1957+032 is a transient low-mass X-ray binary (LMXB) that underwent four short outbursts in 1.5 yr 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 (NS) 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 ∼1.8 to 2.5) as the luminosity decreases. Near the end of its outbursts the observed value of power-law index (Γ) is ∼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 NS.
X-ray: accretion, stars: neutron, X-rays: binaries, individ- ual: MAXI J1957+032
0035-8711
1620-1628
Beri, A.
69ed346a-f02a-4243-83f9-ad5ab4c4008c
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Wijnands, R.
382893ee-0e03-45e3-9321-db8b9fc74914
Degenaar, N.
54149051-d74e-4e43-a7cd-501ec4023511
Parikh, A.S.
21ab1c15-6144-40a1-ac71-618e02bc37d6
Yamaoka, K.
5657d3f1-e732-47c1-bf9f-a4c9a8a077e9
Beri, A.
69ed346a-f02a-4243-83f9-ad5ab4c4008c
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Wijnands, R.
382893ee-0e03-45e3-9321-db8b9fc74914
Degenaar, N.
54149051-d74e-4e43-a7cd-501ec4023511
Parikh, A.S.
21ab1c15-6144-40a1-ac71-618e02bc37d6
Yamaoka, K.
5657d3f1-e732-47c1-bf9f-a4c9a8a077e9

Beri, A., Altamirano, D., Wijnands, R., Degenaar, N., Parikh, A.S. and Yamaoka, K. (2019) Unveiling the nature of compact object in the LMXB MAXI J1957+032 using Swift-XRT. Monthly Notices of the Royal Astronomical Society, 486 (2), 1620-1628. (doi:10.1093/mnras/stz938).

Record type: Article

Abstract

MAXI J1957+032 is a transient low-mass X-ray binary (LMXB) that underwent four short outbursts in 1.5 yr 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 (NS) 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 ∼1.8 to 2.5) as the luminosity decreases. Near the end of its outbursts the observed value of power-law index (Γ) is ∼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 NS.

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More information

Submitted date: 2019
Accepted/In Press date: 29 March 2019
e-pub ahead of print date: 3 April 2019
Published date: June 2019
Keywords: X-ray: accretion, stars: neutron, X-rays: binaries, individ- ual: MAXI J1957+032

Identifiers

Local EPrints ID: 429871
URI: http://eprints.soton.ac.uk/id/eprint/429871
ISSN: 0035-8711
PURE UUID: 05a9d44d-9005-4618-bc5b-fc71c551e25d
ORCID for D. Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

Catalogue record

Date deposited: 08 Apr 2019 16:30
Last modified: 26 Nov 2021 03:02

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Contributors

Author: A. Beri
Author: D. Altamirano ORCID iD
Author: R. Wijnands
Author: N. Degenaar
Author: A.S. Parikh
Author: K. Yamaoka

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