Paper detail

Bondi-Hoyle Accretion around the Non-rotating Black Hole in 4D Einstein-Gauss-Bonnet Gravity

In this paper, the numerical investigation of a Bondi-Hoyle accretion around a non-rotating black hole in a novel four dimensional Einstein-Gauss-Bonnet gravity is investigated by solving the general relativistic hydrodynamical equations using the high resolution shock capturing scheme. For this purpose, the accreated matter from the wind-accreating X-ray binaries falls towards the black hole from the far upstream side of the domain, suphersonically. We study the effects of Gauss-Bonnet coupling constant $α$ in 4D EGB gravity on the accreated matter and shock cones created in the downstream region in detail. The required time having the shock cone in downstream region is getting smaller for alpha > 0 while it is increasing for alpha < 0. It is found that increases in alpha leads violent oscillations inside the shock cone and increases the accretion efficiency. The violent oscillations would cause increase in the energy flux, temperature, and spectrum of X- rays. So the quasi-periodic oscillations (QPOs) are naturally produced inside the shock cone when -5 \leq alpha \leq 0.8. It is also confirmed that EGB black hole solution converges to the Schwarzschild one in general relativity when alpha \rightarrow 0. Besides, the negative coupling constants also give reasonable physical solutions and increase of alpha in negative directions suppresses the possible oscillation observed in the shock cone.