[Previous] | [Session 20] | [Next]

[20.01] Are Ultraluminous X-ray Sources in Nearby Galaxies Intermediate Mass Black Holes?

J. A. Irwin (University of Michigan)

The presence of non-nuclear variable ultraluminous (>10³⁹ ergs s^-1) X-ray sources (ULXs) within nearby galaxies has spawned a flurry of debate regarding the nature of these objects. The X-ray luminosities of the brightest ULXs exceed the Eddington luminosity onto a neutron star by over two orders of magnitude. Taken at face value and assuming the X-ray emission is isotropic, this implies a mass of at least several hundred solar masses for the accreting object -- the much-sought-after intermediate mass black hole (IMBH). However, difficulty in creating a black hole in this mass range has led others to develop alternative descriptions of ULXs involving a black hole of mass ~10 solar masses, in which the high X-ray luminosities are accounted for by anisotropic beaming or super-Eddington accretion. In this talk I will review the properties of ULXs, as well as discuss the pros and cons of the major ULX models.

[Previous] | [Session 20] | [Next]

Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.