The X-ray source M33 X-7 hosts a rapidly spinning, 15.65M¤ black hole orbiting an underluminous, 70M¤ main-sequence companion in a slightly eccentric 3.45-day orbit. Hitherto, there has been no satisfactory explanation for the observed properties. These authors report simulations of evolutionary tracks which reveal that if M33 X-7 started as a primary body of 85M¤–99M¤ and a secondary body of 28M¤–32M¤, in a 2.8–3.1-day orbit, its properties can be consistently explained.
- Francesca Valsecchi
- Evert Glebbeek
- Vassiliki Kalogera
