New Spectral State of Supercritical Accretion Flow with Comptonizing Outflow - Astrophysics > High Energy Astrophysical PhenomenaReport as inadecuate




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Abstract: Supercritical accretion flows inevitably produce radiation-pressure drivenoutflows, which will Compton up-scatter soft photons from the underlyingaccretion flow, thereby making hard emission. We perform two dimensionalradiation hydrodynamic simulations of supercritical accretion flows andoutflows, incorporating such Compton scattering effects, and demonstrate thatthere appears a new hard spectral state at higher photon luminosities than thatof the slim-disk state. In this state, as the photon luminosity increases, thephoton index decreases and the fraction of the hard emission increases. TheCompton $y$-parameter is of the order of unity and thus the photon index willbe $\sim 2$ when the apparent photon luminosity is ${\sim}30L { m E}$ with$L { m E}$ being the Eddington luminosity for nearly face-on sources. Thisexplains the observed spectral hardening of the ULX NGC1313 X-2 in itsbrightening phase and thus supports the model of supercritical accretion ontostellar mass black holes in this ULX.



Author: Tomohisa Kawashima, Ken Ohsuga, Shin Mineshige, Dominikus Heinzeller, Hideaki Takabe, Ryoji Matsumoto

Source: https://arxiv.org/







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