%0 Journal Article
%T Cutoff in the hard X-ray spectra of the ultraluminous X-ray sources HoIX X-1 and M82 X-1
%A Sergey Sazonov
%A Alexander Lutovinov
%A Roman Krivonos
%J Physics
%D 2013
%I arXiv
%R 10.1134/S1063773714030062
%X 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.
%U http://arxiv.org/abs/1312.1777v1