Dynamical Evolution of the Shock Cone around $4D$ Einstein-Gauss Bonnet Rotating Black Hole

TL;DR

This study investigates the behavior of shock cones formed during accretion onto rotating black holes in Einstein-Gauss-Bonnet gravity, revealing how the Gauss-Bonnet coupling influences accretion dynamics and observable features.

Contribution

It introduces a detailed analysis of shock cone dynamics in Einstein-Gauss-Bonnet gravity, highlighting the effects of the coupling constant and black hole spin on accretion properties.

Findings

Higher Gauss-Bonnet alpha increases oscillation amplitude in accretion rate.

Negative alpha values lead to smaller shock opening angles.

Black hole spin correlates with higher accretion rates.

Abstract

In this paper, a Bondi-Hoyle accretion onto the rotating black hole in Einstein-Gauss Bonnet gravity is studied. By injecting the gas from the upstream region of the computational domain, we have found the occurrence of the stable shock cones in the downstream region. The dynamical structures and oscillation properties of these shock cones strongly depend on the black hole spin parameter $a$ and Gauss-Bonnet coupling constant alpha. It is found that the various values of alpha can lead the different amounts of matter to pile up close to the black hole horizon, higher alpha causes bigger oscillation amplitude in the mass accretion rate, and the required time to reach the steady-state is getting smaller with the increase in alpha. Moreover, increasing alpha in the negative direction causes a decrease in the shock opening angle and this angle slightly increases with the increasing $\alpha$ in the positive direction. We found that the negative values of Gauss-Bonnet coupling constant are more favored to have interesting physical outcomes such as accretion rate and oscillation. In addition, the higher the black hole rotation parameter (a) emerges the higher the accretion rate. It is also confirmed that, for alpha \rightarrow 0, the black hole solution in EGB gravity converges to Kerr in general relativity. Furthermore, Gauss-Bonnet coupling constant could be used to constrain the size of the observed shadow of M87* radius for various values of the black hole rotation parameter.