Timing the Pulsations of the Accreting Millisecond Pulsar SAX J1808.4–3658 during Its 2019 Outburst
Author(s)Bult, Peter; Chakrabarty, Deepto; Arzoumanian, Zaven; Gendreau, Keith C.; Guillot, Sebastien; Malacaria, Christian; Ray, Paul. S.; Strohmayer, Tod E.; ... Show more Show less
MetadataShow full item record
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.
DepartmentMIT Kavli Institute for Astrophysics and Space Research
American Astronomical Society
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
Final published version