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Paper: Peculiar Characteristics of a Hyper-luminous X-ray Source in M82
Volume: 289, The Proceedings of the IAU 8th Asian-Pacific Regional Meeting, Volume I
Page: 291
Authors: Matsumoto, H.; Tsuru, T. G.; Watari, K.; Mineshige, S.; Matsushita, S.
Abstract: M82 X-1, which is the brightest X-ray source in M82, is a strong candidate for an intermediate mass black hole of 10^3 -- 10^6 M_o. Since M82 X-1 is much brighter than ultra-luminous X-ray sources (ULXs), we call it a hyper-luminous X-ray source (HLX). We analyzed the ASCA spectra of M82 X-1 by using the multi-color disk (MCD) blackbody model, and found that the MCD model can describe the spectra of M82 X-1 as well as those of ULXs. Not only the bolometric luminosity L_bol) but also the innermost disk temperature (T_in) of M82 X-1 is higher than those of ULXs. The most striking feature is that there is no correlation between T_in and L_bol, while there is a positive correlation between those of ULXs. A lower limit on the mass of M82 X-1 obtained by assuming that L_bol is sub-Eddington is much larger than an upper limit obtained by assuming that the innermost disk radius (R_in) is larger than the gravitational radius of a black hole (BH). These characteristics are not consistent with theoretical models such as a standard accretion disk model with a Kerr BH, a slim disk model, and a beaming model, all of which might be able to explain ULXs. This may suggest either that some important processes we overlook play an important role in such luminous objects, or that the HLX is a different kind of object from ULXs.
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