Testing relativistic reflection models with GRMHD simulations of accreting black holes

TL;DR

This paper uses GRMHD simulations and ray-tracing to evaluate the accuracy of relativistic reflection models in measuring black hole parameters, highlighting their effectiveness at high inclinations and minor discrepancies at low inclinations.

Contribution

It introduces a method to test reflection models against simulated realistic accretion disk spectra in Kerr spacetime.

Findings

Reflection models recover parameters accurately at high inclination angles.

Minor discrepancies occur at low inclination angles.

Simulation-based validation of reflection models for black hole studies.

Abstract

X-ray reflection spectroscopy is currently one of the leading techniques for studying the inner part of accretion disks around black holes, measuring black hole spins, and even testing fundamental physics in strong gravitational fields. However, the accuracy of these measurements depends on the reflection models employed for the spectral analysis, which are sometimes questioned. In this work, we use a general relativistic magnetohydrodynamic (GRMHD) code to generate a thin accretion disk in Kerr spacetime and ray-tracing techniques to calculate its relativistically broadened reflection spectrum. We simulate NuSTAR observations and we test the capability of current reflection models based on Novikov-Thorne disks to recover the correct input parameters. Our study shows that we can measure the correct input parameters in the case of high inclination angle sources, while we find some minor discrepancy when the inclination angle of the disk is low.