  We study the origin of the ultraluminous X-ray source M82-X1 in the nearby
starburst galaxy M82. This X-ray source is of particular interest as it is
currently the best candidate intermediate mass black hole; it is associated
with a 54mHz quasi periodic oscillations with a relatively low (~1keV)
black-body temperature.
  We perform detailed binary evolution calculations of 2--15Msun stars which
transfer mass to a 100--2000Msun 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-X1 is a 10-15Msun
star near the end of its main-sequence or slightly evolved, which transfers
mass to a ~1000Msun 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.
