General Relativistic Numerical Simulation of sub-Keplerian Transonic Accretion Flows onto Rotating Black Holes: Kerr Spacetime

TL;DR

This paper presents the first general relativistic numerical simulations of sub-Keplerian transonic accretion flows onto rotating black holes, revealing steady shock solutions in two dimensions that could help measure black hole spins via spectral analysis.

Contribution

It introduces a novel 2D simulation of advective flows around Kerr black holes, demonstrating steady shock formation in a regime where none was previously known.

Findings

Steady shock waves form in 2D accretion flows around rotating black holes.

Simulations match theoretical results in 1D, validating the code.

Shock regions could influence observed spectra and aid in spin measurement.

Abstract

We study time evolution of sub-Keplerian transonic accretion flows onto black holes using a general relativistic numerical simulation code. We perform simulations around the black holes having non-zero rotation. We first compare one-dimensional simulation results with theoretical results and validate the performance of our code. Next, we present results of axisymmetric, two-dimensional simulation of advective flows. In the literature, there is no solution which describes steady shock solutions in two dimensions. However, our simulations produce these centrifugal force supported steady shock waves even in presence of strong dragging of inertial frames. Since the post-shock region could be hot and upscatter photons through Comptonization, these shock would put imprints on the spectra. Thus, our solutions, which represent truly new results, could be useful to measure spins through radiation spectrum of accreting Kerr black holes.