On the Formation of Ultraluminous X-ray Sources with Neutron Star Accretors: the Case of M82 X-2

Jan 12, 2015
6 pages
Published in:
  • Astrophys.J.Lett. 802 (2015) 1, L5
  • Published: Mar 19, 2015
e-Print:

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Abstract: (arXiv)
The recent discovery of a neutron star accretor in the ultra-luminous X-ray source M82 X-2 challenges our understanding of high-mass X-ray binary formation and evolution. By combining binary population synthesis and detailed mass-transfer models, however, we show that the binary parameters of M82 X-2 are not surprising provided non-conservative mass transfer is allowed. Specifically, the donor-mass lower limit and orbital period measured for M82 X-2 lie near the most probable values predicted by population synthesis models, and systems such as M82 X-2 should exist in approximately 13% of the galaxies with a star-formation history similar to M82. We conclude that the binary system that formed M82 X-2 is most likely less than 50 Myr old and contains a donor star which had an initial mass of approximately 8-10 M_\odot, while the NS's progenitor star had an initial mass in the 825M8-25\,\rm M_{\odot} range. The donor star still currently resides on the main sequence, and is capable of continued MT on the thermal timescale, while in the ultra-luminous X-ray regime, for as long as 400,000 years.
Note:
  • 6 pages, 4 Figures, The Astrophysical Journal Letters (in press)