GRMHD beyond Kerr: An extension of the HARM code for thin disks to non-Kerr spacetimes

Abstract

Black hole based tests of general relativity have proliferated in recent times with new and improved detectors and telescopes. Modelling of the black hole neighborhood, where most of the radiation carrying strong-field signature originates, is of utmost importance for robust and accurate constraints on possible violations of general relativity. As a first step, this paper presents the extension of general relativistic magnetohydrodynamic simulations of thin accretion disks to parametrically deformed black holes that generalize the Kerr solution. The extension is based on \textsc{harmpi}, a publicly available member of the \textsc{harm} family of codes, and uses a phenomenological metric to study parametric deviations away from Kerr. The extended model is used to study the disk structure, stability, and radiative efficiency. We also compute the Fe K$\alpha$ profiles in simplified scenarios and present an outlook for the future.