Peculiar Characteristics of the Hyper-Luminous X-Ray Source M82 X-1

Abstract

M82 X-1 is the strongest candidate for an intermediate-mass black hole. The peak luminosity of M82 X-1 is higher than those of ultra-luminous X-ray sources (ULXs) by more than one order of magnitude. We therefore call this object a hyper-luminous X-ray source (HLX). To clarify what is going on in such a luminous object, we analyzed the ASCA spectrum of M82 X-1. Since the spatial resolution of ASCA is not sufficient to resolve M82 X-1, we estimated the contamination from X-ray sources other than M82 X-1 by using Chandra. The spectrum of M82 X-1 can be fitted by the multi-color disk model, and we found that there is no correlation between the innermost disk temperature and the X-ray luminosity, which is quite different from ULXs. The results are not consistent with theoretical models such as standard accretion disk model with a Kerr black hole, and a slim disk model.