Cutoff in the hard X-ray spectra of the ultraluminous X-ray sources HoIX X-1 and M82 X-1

Abstract

Using data from the XMM-Newton and INTEGRAL observatories, we have detected a cutoff at energies above 10 keV in the X-ray spectra of the ultraluminous X-ray sources HoIX X-1 and M82 X-1. The spectra obtained can be described by a model of Comptonization of radiation in a gas cloud of moderate temperature (kT~2-3 keV) and high optical depth (tau~15-25). Such conditions can be fulfilled during supercritical accretion of matter onto a stellar-mass black hole accompanied by a strong gas outflow. The results of this work confirm the existence of a spectral state specific to ultraluminous X-ray sources, which is unlike any of the known spectral states in normal X-ray binaries.

8 pages, 5 figures, accepted for publication in Astronomy Letters

References in corpus (4)

• Super-critically accreting stellar-mass black holes as ultraluminous X-ray sources
• XMM-Newton observations of the brightest Ultraluminous X-ray sources
• Masses, Beaming and Eddington Ratios in Ultraluminous X-ray Sources
• Optical Properties of the Ultraluminous X-ray Source Holmberg IX X-1 and its Stellar Environment

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