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Fe Kα Profiles from Simulations of Accreting Black Holes
By Brooks E. Kinch, Jeremy D. Schnittman, Timothy R. Kallman, Julian H. Krolik
Published in The Astrophysical Journal 826, 52 (Wednesday, July 20, 2016)


We present the first results from a new technique for the prediction of Fe Kα profiles directly from general relativistic magnetohydrodynamic (GRMHD) simulations. Data from a GRMHD simulation are processed by a Monte Carlo global radiation transport code, which determines the X-ray flux irradiating the disk surface and the coronal electron temperature self-consistently. With that irradiating flux and the disk's density structure drawn from the simulation, we determine the reprocessed Fe Kα emission from photoionization equilibrium and solution of the radiation transfer equation. We produce maps of the surface brightness of Fe Kα emission over the disk surface, which—for our example of a $10{M}_{\odot }$ Schwarzschild black hole accreting at 1% the Eddington value—rises steeply one gravitational radius outside the radius of the innermost stable circular orbit and then falls ∝r −2 at larger radii. We explain these features of the Fe Kα radial surface brightness profile as consequences of the disk's ionization structure and an extended coronal geometry, respectively. We also present the corresponding Fe Kα line profiles as would be seen by distant observers at several inclinations. Both the shapes of the line profiles and the equivalent widths of our predicted Kα lines are qualitatively similar to those typically observed from accreting black holes. Most importantly, this work represents a direct link between theory and observation: in a fully self-consistent way, we produce observable results—iron fluorescence line profiles—from the theory of black hole accretion with almost no phenomenological assumptions.