Spectral Analyses of the Nearest Persistent Ultraluminous X-Ray Source M33 X-8 - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




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Abstract: We provide a detailed analysis of 12 XMM observations of the nearestpersistent extragalactic ultraluminous X-ray source ULX, M33 X-8. Nosignificant spectral evolution is detected between the observations, thereforewe combine the individual observations to increase the signal-to-noise ratiofor spectral fitting. The combined spectra are best fitted by theself-consistent p-free disk plus power-law component model with p =0.571 {-0.030}^{+0.032}, kT {in} = 1.38 {-0.08}^{+0.09} keV, and the flux ratioof the p-free disk component to the power-law component being 0.63:0.37 in the0.3 - 10 keV band. The fitting indicates that the black hole in M33 X-8 is of\sim 10 M {\odot} and accretes at a super-Eddington rate \sim 1.5 L {Edd},and the phase of the accretion disk is close to a slim disk p = 0.5. Wereport, for the first time, that an extra power-law component is required inaddition to the p-free disk model for ULXs. In super-Eddington cases, thepower-law component may possibly result from the optically thin inner region fthe disk or a comptonized corona similar to that of a standard thin disk.



Autor: Shan-Shan Weng, Jun-Xian Wang, Wei-Min Gu, Ju-Fu Lu

Fuente: https://arxiv.org/







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