MAXI J1957+032: a new accreting millisecond X-ray pulsar in an ultra-compact binary
MAXI J1957+032: a new accreting millisecond X-ray pulsar in an ultra-compact binary
The detection of coherent X-ray pulsations at ∼314 Hz (3.2 ms) classifies MAXI J1957+032 as a fast-rotating, accreting neutron star. We present the temporal and spectral analysis performed using NICER observations collected during the latest outburst of the source. Doppler modulation of the X-ray pulsation revealed the ultra-compact nature of the binary system characterized by an orbital period of ∼1 h and a projected semimajor axis of 14 lt-ms. The neutron star binary mass function suggests a minimum donor mass of 1.7 × 10−2 M⊙, assuming a neutron star mass of 1.4 M⊙ and a binary inclination angle lower than 60 deg. This assumption is supported by the lack of eclipses or dips in the X-ray light curve of the source. We characterized the 0.5–10 keV energy spectrum of the source in outburst as the superposition of a relatively cold black-body-like thermal emission compatible with the emission from the neutron star surface and a Comptonization component with photon index consistent with a typical hard state. We did not find evidence for iron K α lines or reflection components.
L76–L80
Sanna, A.
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Bult, P.
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Ng, M.
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Ray, P.S.
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Jaisawal, G.K.
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Burderi, L.
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Di Salvo, T.
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Riggio, A.
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Altamirano, D.
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Strohmayer, T.E.
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Manca, A.
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Gendreau, K.C.
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Chakrabarty, D.
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Iwakiri, W.
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Iaria, R.
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30 August 2022
Sanna, A.
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Bult, P.
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Ng, M.
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Ray, P.S.
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Jaisawal, G.K.
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Burderi, L.
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Di Salvo, T.
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Riggio, A.
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Altamirano, D.
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Strohmayer, T.E.
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Manca, A.
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Gendreau, K.C.
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Chakrabarty, D.
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Iwakiri, W.
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Iaria, R.
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Sanna, A., Bult, P., Ng, M., Ray, P.S., Jaisawal, G.K., Burderi, L., Di Salvo, T., Riggio, A., Altamirano, D., Strohmayer, T.E., Manca, A., Gendreau, K.C., Chakrabarty, D., Iwakiri, W. and Iaria, R.
(2022)
MAXI J1957+032: a new accreting millisecond X-ray pulsar in an ultra-compact binary.
Monthly Notices of the Royal Astronomical Society: Letters, 516 (1), .
(doi:10.1093/mnrasl/slac093).
Abstract
The detection of coherent X-ray pulsations at ∼314 Hz (3.2 ms) classifies MAXI J1957+032 as a fast-rotating, accreting neutron star. We present the temporal and spectral analysis performed using NICER observations collected during the latest outburst of the source. Doppler modulation of the X-ray pulsation revealed the ultra-compact nature of the binary system characterized by an orbital period of ∼1 h and a projected semimajor axis of 14 lt-ms. The neutron star binary mass function suggests a minimum donor mass of 1.7 × 10−2 M⊙, assuming a neutron star mass of 1.4 M⊙ and a binary inclination angle lower than 60 deg. This assumption is supported by the lack of eclipses or dips in the X-ray light curve of the source. We characterized the 0.5–10 keV energy spectrum of the source in outburst as the superposition of a relatively cold black-body-like thermal emission compatible with the emission from the neutron star surface and a Comptonization component with photon index consistent with a typical hard state. We did not find evidence for iron K α lines or reflection components.
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author accepted manuscript - AAM
More information
Accepted/In Press date: 11 August 2022
e-pub ahead of print date: 16 August 2022
Published date: 30 August 2022
Identifiers
Local EPrints ID: 491634
URI: http://eprints.soton.ac.uk/id/eprint/491634
ISSN: 1745-3925
PURE UUID: 52680aa7-183e-48f0-b5c7-48e0d7a731b7
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Date deposited: 03 Jul 2024 09:11
Last modified: 12 Jul 2024 01:51
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Contributors
Author:
A. Sanna
Author:
P. Bult
Author:
M. Ng
Author:
P.S. Ray
Author:
G.K. Jaisawal
Author:
L. Burderi
Author:
T. Di Salvo
Author:
A. Riggio
Author:
T.E. Strohmayer
Author:
A. Manca
Author:
K.C. Gendreau
Author:
D. Chakrabarty
Author:
W. Iwakiri
Author:
R. Iaria
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