Timing the Pulsations of the Accreting Millisecond Pulsar SAX J1808.4–3658 during Its 2019 Outburst
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Bult_2020_ApJ_898_38.pdf
Description
Published version
Size
1012.29 KB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Bult, Peter
Chakrabarty, Deepto
Arzoumanian, Zaven
Gendreau, Keith C.
Guillot, Sebastien
Malacaria, Christian
Ray, Paul. S.
Strohmayer, Tod E.
Date Issued
July 2020
Journal
Astrophysical Journal
Publisher
American Astronomical Society
Citation
Bult, Peter et al. "Timing the Pulsations of the Accreting Millisecond Pulsar SAX J1808.4–3658 during Its 2019 Outburst. " Astrophysical Journal 898, 1 (July 2020): 38 © 2020 The American Astronomical Society
Version
Final published version
Abstract
In this paper we present a coherent timing analysis of the 401 Hz pulsations of the accreting millisecond X-ray pulsar SAX J1808.4-3658 during its 2019 outburst. Using observations collected with the Neutron Star Interior Composition Explorer (NICER), we establish the pulsar spin frequency and orbital phase during its latest epoch. We find that the 2019 outburst shows a pronounced evolution in pulse phase over the course of the outburst. These phase shifts are found to correlate with the source flux and are interpreted in terms of hot-spot drift on the stellar surface, driven by changes in the mass accretion rate. Additionally, we find that the long-term evolution of the pulsar spin frequency shows evidence for a modulation at the Earth's orbital period, allowing for pulsar timing based astrometry of this accreting millisecond pulsar.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.3847/1538-4357/ab9827
