General relativistic magnetohydrodynamic Bondi–Hoyle accretion

In this paper, we present a fully relativistic study of axisymmetric magnetohydrodynamic (MHD) Bondi–Hoyle accretion on to a moving Kerr black hole. The equations of general relativistic MHD are solved using high-resolution shock-capturing methods. In this treatment, we consider the ideal MHD limit. The parameters of interest in this study are the adiabatic constant , the asymptotic speed of sound c∞s and the plasma β parameter βP. We focus the investigation on the parameter regime in which the flow is supersonic or when v ∞ ≥ c∞s. In some cases, subsonic asymptotic flows are considered for comparison purposes. We study the accretion rates of the total energy and momenta, as well as the hydrodynamic energy and momentum accretion rates. The models presented in this study exhibit a matter density depletion in the downstream region of the black hole which tends to vacuum (ρ0 = 0) in convergence tests. This feature is due to the presence of the magnetic field, more specifically the magnetic pressure, and is not seen in previous purely hydrodynamic studies. Key words: accretion, accretion discs – black hole physics – magnetic fields – MHD – shock waves – methods: numerical