NICER Discovery of Millisecond X-Ray Pulsations and an Ultracompact Orbit in IGR J17494-3030
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Ng_2021_ApJL_908_L15.pdf
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Published version
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Author(s)
Ng, Mason
Ray, Paul S.
Bult, Peter
Chakrabarty, Deepto
Jaisawal, Gaurava K.
Malacaria, Christian
Altamirano, Diego
Arzoumanian, Zaven
Gendreau, Keith C.
Güver, Tolga
Date Issued
February 2021
Journal
Astrophysical Journal Letters
Publisher
American Astronomical Society
Citation
Ng, Mason, Ray, Paul S, Bult, Peter, Chakrabarty, Deepto, Jaisawal, Gaurava K et al. 2021. "NICER Discovery of Millisecond X-Ray Pulsations and an Ultracompact Orbit in IGR J17494-3030." Astrophysical Journal Letters, 908 (1).
Version
Final published version
Abstract
© 2021. The American Astronomical Society. 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.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/2041-8213/abe1b4
