The Discovery of the 528.6 Hz Accreting Millisecond X-Ray Pulsar MAXI J1816-195

Bult P., Altamirano D., Arzoumanian Z., Chakrabarty D., Chenevez J., Ferrara E. C., ...More

Astrophysical Journal Letters, vol.935, no.2, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 935 Issue: 2
  • Publication Date: 2022
  • Doi Number: 10.3847/2041-8213/ac87f9
  • Journal Name: Astrophysical Journal Letters
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, INSPEC, Directory of Open Access Journals
  • Istanbul University Affiliated: Yes


© 2022. The Author(s). Published by the American Astronomical Society.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.