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 (1) , Tolga Güver , Wataru Iwakiri , Gaurava K. Jaisawal , Giulio C. Mancuso , Christian Malacaria , Mason Ng , Andrea Sanna , Tod E. Strohmayer , Zorawar Wadiasingh , Michael T. Wolff

1 IRAP - Institut de recherche en astrophysique et planétologie

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 hr and a projected semimajor axis of 0.26 lt-s for the pulsar, which constrains the mass of the donor star to 0.10-0.55 M _⊙. 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 hr. We did not detect evidence for photospheric radius expansion, placing an upper limit on the source distance of 8.6 kpc.

Keywords: Low-mass x-ray binary stars; Millisecond pulsars; X-ray bursts; Astrophysics - High Energy Astrophysical Phenomena

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Peter Bult, Diego Altamirano, Zaven Arzoumanian, Deepto Chakrabarty, Jérôme Chenevez, et al.. The Discovery of the 528.6 Hz Accreting Millisecond X-Ray Pulsar MAXI J1816-195. The Astrophysical journal letters, 2022, 935, ⟨10.3847/2041-8213/ac87f9⟩. ⟨insu-03863536⟩