Bondi–Hoyle accretion around the non-rotating black hole in 4D Einstein–Gauss–Bonnet gravity

AbstractIn 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, supersonically. We study the effects of Gauss–Bonnet coupling constant $$\alpha $$ 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 $$\alpha > 0$$ α > 0 while it is increasing for $$\alpha < 0$$ α < 0 . It is found that increases in $$\alpha $$ α 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 $$-5 \le \alpha \le 0.8$$ - 5 ≤ α ≤ 0.8 . It is also confirmed that EGB black hole solution converges to the Schwarzschild one in general relativity when $$\alpha \rightarrow 0$$ α → 0 . Besides, the negative coupling constants also give reasonable physical solutions and increase of $$\alpha $$ α in negative directions suppresses the possible oscillation observed in the shock cone.