X-Ray Emissions from Three-Dimensional Magnetohydrodynamic Coronal Accretion Flows

Abstract

Abstract We calculated the radiation spectrum and its time variability of a black-hole accretion disk-corona system based on a three-dimensional magnetohydrodynamic (MHD) simulation. In explaining the spectral properties of active galactic nuclei, it is often assumed that they consist of a geometrically thin, optically thick disk and hot, optically thin corona surrounding the thin disk. As for a model of the corona, we adopted the simulation data of three-dimensional, non-radiative MHD accretion flows calculated by Y. Kato and coworkers, while for a thin disk we assumed a standard-type disk. We performed Monte-Carlo radiative transfer simulations of the corona, while taking into account the Compton scattering of soft photons from the thin disk by hot thermal electrons and coronal irradiation heating of the thin disk, which emits blackbody radiation. By adjusting the density parameter of the MHD coronal flow, we could produce emergent spectra that are consistent with those of typical Seyfert galaxies. Moreover, we found rapid time variability in the X-ray emission spectra, originating from a density fluctuation produced by a magnetorotational instability in the MHD corona. The features of reflection component including iron fluorescent line emission are also briefly discussed.