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P. Kaaret (Harvard-Smithsonian CfA), S. Corbel (CEA/Saclay), A.H. Prestwich, A. Zezas (Harvard-Smithsonian CfA)
The physical nature of ultraluminous x-ray sources is uncertain. Stellar mass black holes with beamed radiation and intermediate black holes with isotropic radiation are two plausible explanations. We discovered radio emission from an ultraluminous x-ray source in the dwarf irregular galaxy NGC 5408. The x-ray, radio and optical fluxes as well as the x-ray spectral shape are consistent with beamed relativistic jet emission from an accreting stellar black hole. If confirmed, this would suggest that the ultraluminous x-ray sources may be stellar-mass rather than intermediate mass black holes. However, interpretation of the source as a jet-producing intermediate-mass black hole cannot be ruled out at this time.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.