Intermediate mass black holes in accreting binaries: Formation, evolution and observational appearance

We study the origin of the ultraluminous X-ray source M82 X-1 in the nearby starburst galaxy M82. This X-ray source is of particular interest as it is currently the best candidate for an intermediate mass black hole; it is associated with a 54 mHz quasi-periodic oscillation with a relatively low (∼1 keV) blackbody temperature. We perform detailed binary evolution calculations of 2-15 M_⊙ stars which transfer mass to a 100-2000 M_⊙ black hole and present an empirical model for the X-ray characteristics expected for such binaries. Based on the binary evolution calculations and the assumption in our simulations we conclude that the most likely candidate for the bright X-ray source M82 X-l is a 10-15 M _⊙ star near the end of its main sequence or slightly evolved, which transfers mass to a ∼1000 M_⊙ black hole. We expect the system to be in the high/soft state. In that case the binary will not be visible as a source of gravitational wave radiation, but other transient X-ray binaries with lower mass donors way be rather bright sources of gravitational wave radiation.