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NICER discovery of millisecond x-ray pulsations and an ultracompact orbit in IGR J17494-3030

NICER discovery of millisecond x-ray pulsations and an ultracompact orbit in IGR J17494-3030
NICER discovery of millisecond x-ray pulsations and an ultracompact orbit in IGR J17494-3030

We report the detection of 376.05 Hz (2.66 ms) coherent X-ray pulsations in NICER observations of a transient outburst of the low-mass X-ray binary IGR J17494-3030 in 2020 October/November. The system is an accreting millisecond X-ray pulsar in a 75-minute ultracompact binary. The mass donor is most likely a ≃0.02M⊙ finiteentropy white dwarf composed of He or C/O. The fractional rms pulsed amplitude is 7.4%, and the soft (1-3 keV) X-ray pulse profile contains a significant second harmonic. The pulsed amplitude and pulse phase lag (relative to our mean timing model) are energy dependent, each having a local maximum at 4 and 1.5 keV, respectively. We also recovered the X-ray pulsations in archival 2012 XMM-Newton observations, allowing us to measure a longterm pulsar spin-down rate of ν= -2.1(7) × 10-14 Hz s-1 and to infer a pulsar surface dipole magnetic field strength of ≃109 G. We show that the mass transfer in the binary is likely nonconservative, and we discuss various scenarios for mass loss from the system.

2041-8205
Ng, Mason
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Ray, Paul S.
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Bult, Peter
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Chakrabarty, Deepto
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Jaisawal, Gaurava K.
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Malacaria, Christian
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Altamirano, Diego
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Arzoumanian, Zaven
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Gendreau, Keith C.
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Güver, Tolga
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Kerr, Matthew
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Strohmayer, Tod E.
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Wadiasingh, Zorawar
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Wolff, Michael T.
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Ng, Mason
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Ray, Paul S.
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Bult, Peter
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Chakrabarty, Deepto
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Jaisawal, Gaurava K.
4d5dcd39-0881-426d-8ad7-f378238405ae
Malacaria, Christian
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Altamirano, Diego
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Arzoumanian, Zaven
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Gendreau, Keith C.
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Güver, Tolga
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Kerr, Matthew
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Strohmayer, Tod E.
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Wadiasingh, Zorawar
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Wolff, Michael T.
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Ng, Mason, Ray, Paul S., Bult, Peter, Chakrabarty, Deepto, Jaisawal, Gaurava K., Malacaria, Christian, Altamirano, Diego, Arzoumanian, Zaven, Gendreau, Keith C., Güver, Tolga, Kerr, Matthew, Strohmayer, Tod E., Wadiasingh, Zorawar and Wolff, Michael T. (2021) NICER discovery of millisecond x-ray pulsations and an ultracompact orbit in IGR J17494-3030. Astrophysical Journal Letters, 908 (1), [L15]. (doi:10.3847/2041-8213/abe1b4).

Record type: Article

Abstract

We report the detection of 376.05 Hz (2.66 ms) coherent X-ray pulsations in NICER observations of a transient outburst of the low-mass X-ray binary IGR J17494-3030 in 2020 October/November. The system is an accreting millisecond X-ray pulsar in a 75-minute ultracompact binary. The mass donor is most likely a ≃0.02M⊙ finiteentropy white dwarf composed of He or C/O. The fractional rms pulsed amplitude is 7.4%, and the soft (1-3 keV) X-ray pulse profile contains a significant second harmonic. The pulsed amplitude and pulse phase lag (relative to our mean timing model) are energy dependent, each having a local maximum at 4 and 1.5 keV, respectively. We also recovered the X-ray pulsations in archival 2012 XMM-Newton observations, allowing us to measure a longterm pulsar spin-down rate of ν= -2.1(7) × 10-14 Hz s-1 and to infer a pulsar surface dipole magnetic field strength of ≃109 G. We show that the mass transfer in the binary is likely nonconservative, and we discuss various scenarios for mass loss from the system.

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NICER discovery of millisecond x-ray pulsations and an ultracompact orbit in IGR J17494-3030 - Accepted Manuscript
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Accepted/In Press date: 31 January 2021
e-pub ahead of print date: 15 February 2021
Published date: February 2021
Additional Information: Publisher Copyright: © 2021. The American Astronomical Society.

Identifiers

Local EPrints ID: 447851
URI: http://eprints.soton.ac.uk/id/eprint/447851
ISSN: 2041-8205
PURE UUID: d36a8ef0-ea90-4e49-b118-a3b8ac3f1f9d
ORCID for Diego Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

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Date deposited: 24 Mar 2021 18:30
Last modified: 17 Mar 2024 06:25

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Contributors

Author: Mason Ng
Author: Paul S. Ray
Author: Peter Bult
Author: Deepto Chakrabarty
Author: Gaurava K. Jaisawal
Author: Christian Malacaria
Author: Zaven Arzoumanian
Author: Keith C. Gendreau
Author: Tolga Güver
Author: Matthew Kerr
Author: Tod E. Strohmayer
Author: Zorawar Wadiasingh
Author: Michael T. Wolff

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