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arXiv · 2208.04721

The discovery of the 528.6 Hz accreting millisecond X-ray pulsar MAXI J1816-195

Peter Bult·Diego Altamirano·Zaven Arzoumanian·Deepto Chakrabarty·Jérôme Chenevez·Elizabeth C. Ferrara·Keith C. Gendreau·Sebastien Guillot·Tolga Güver·Wataru Iwakiri·Gaurava K. Jaisawal·Giulio C. Mancuso·Christian Malacaria·Mason Ng·Andrea Sanna·Tod E. Strohmayer·Zorawar Wadiasingh·Michael T. Wolff
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Abstract

We present the discovery of 528.6 Hz pulsations in the new X-ray transient MAXI J1816-195. Using NICER, we observed the first recorded transient outburst from the neutron star low-mass X-ray binary MAXI J1816-195 over a period of 28 days. From a timing analysis of the 528.6 Hz pulsations, we find that the binary system is well described as a circular orbit with an orbital period of 4.8 hours and a projected semi-major axis of 0.26 light-seconds for the pulsar, which constrains the mass of the donor star to $0.10-0.55 M_\odot$. Additionally, we observed 15 thermonuclear X-ray bursts showing a gradual evolution in morphology over time, and a recurrence time as short as 1.4 hours. We did not detect evidence for photospheric radius expansion, placing an upper limit on the source distance of 8.6 kpc.

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Peter Bult, Diego Altamirano, Zaven Arzoumanian, Deepto Chakrabarty, Jérôme Chenevez, Elizabeth C. Ferrara, Keith C. Gendreau, Sebastien Guillot, Tolga Güver, Wataru Iwakiri, Gaurava K. Jaisawal, Giulio C. Mancuso, Christian Malacaria, Mason Ng, Andrea Sanna, Tod E. Strohmayer, Zorawar Wadiasingh, Michael T. Wolff. 2022-08-09. The discovery of the 528.6 Hz accreting millisecond X-ray pulsar MAXI J1816-195. https://doi.org/10.3847/2041-8213%2Fac87f9

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