A Population of Ultraluminous X-Ray Sources with an Accreting Neutron Star
Abstract
Most ultraluminous X-ray sources (ULXs) are believed to be X-ray binary systems, but previous observational and theoretical studies tend to prefer a black hole rather than a neutron star (NS) accretor. The recent discovery of 1.37 s pulsations from the ULX M82 X-2 has established its nature as a magnetized NS. In this work we model the formation history of NS ULXs in an M82- or Milky Way (MW)-like Galaxy, by use of both binary population synthesis and detailed binary evolution calculations. We find that the birth rate is around 10-4 yr-1 for the incipient X-ray binaries in both cases. We demonstrate the distribution of the ULX population in the donor mass-orbital period plane. Our results suggest that, compared with black hole X-ray binaries, NS X-ray binaries may significantly contribute to the ULX population, and high-mass and intermediate-mass X-ray binaries dominate the NS ULX population in M82- and MW-like Galaxies, respectively.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2015
- DOI:
- 10.1088/0004-637X/802/2/131
- arXiv:
- arXiv:1502.03905
- Bibcode:
- 2015ApJ...802..131S
- Keywords:
-
- accretion;
- accretion disks;
- stars: evolution;
- stars: neutron;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 13 pages, 5 figures, accepted for publication in ApJ