The Discovery of the 528.6 Hz Accreting Millisecond X-Ray Pulsar MAXI J1816-195
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 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2022
- DOI:
- 10.3847/2041-8213/ac87f9
- arXiv:
- arXiv:2208.04721
- Bibcode:
- 2022ApJ...935L..32B
- Keywords:
-
- Low-mass x-ray binary stars;
- Millisecond pulsars;
- X-ray bursts;
- 939;
- 1062;
- 1814;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 8 pages, 3 figures, 2 tables. Accepted for publication in ApJ Letters