A review of ultra luminous X-ray sources

This talk will review the observational characteristics of ULXs in nearby galaxies, and will present the new Chandra data on the ULX population of the Antennae. ULXs are exciting sources because they may be due to Intermediate Mass Black Holes (IMBH, m > 100 Msol), however this extraordinary claim requires a high level of scrutiny. Alternate models involving beamed radiation have been proposed, that do not require IMBHs. The observational implications for these different models will be discussed.