The NuSTAR Ultraluminous X-ray Source Program

The origin of the extreme luminosities displayed by ultraluminous X-ray sources (ULXs) may relate to either super-Eddington accretion or the presence of black holes more massive than standard stellar remnants, e.g. intermediate mass black holes with masses of 100's or 1000's of solar masses. As yet, this origin remains undetermined despite significant observational efforts with soft X-ray missions. The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, will probe the hard X-ray emission from ULXs, opening up a new observational window into these enigmatic sources. In combination with coordinated XMM-Newton and Suzaku observations providing simultaneous soft X-ray coverage, these high energy observations will provide unprecedented broadband X-ray spectra for a sample of highly luminous ULXs in the first two years of operation, allowing us to further probe the nature of these sources. Here, we discuss plans and predictions for the NuSTAR ULX program, and highlight some early results from this program.