General-relativistic Bondi-Hoyle-Lyttleton accretion in a toroidally magnetized medium

Abstract

The dynamics of a black hole traveling through a plasma -- a general relativistic extension of the classic Bondi-Hoyle-Lyttleton (BHL) accretion problem -- can be related to a variety of astrophysical contexts, including the aftermath of binary black hole mergers in gaseous environments. We perform three-dimensional general relativistic magnetohydrodynamics simulations of BHL accretion onto a rotating black hole for an incoming flow with a toroidal (inclined) magnetization with respect to the spin axis of the black hole. Irrespective of inclination but dependent on the wind speed, we find that the accretion flow onto the black hole can become magnetically arrested, launching an intermittent (and sometimes striped) jet. The upstream ram pressure of the wind bends the jet, and confines the angular extent into which the magnetic flux tubes ejected from quasi-periodic eruptions are released. Recoil from magnetic flux eruptions drives strong oscillations in the accretion plane, resulting in jet nutation at the outer radii and occasionally ripping off the inner part of the accretion disk. In addition to dynamical friction, the black hole experiences a perpendicular drag force analogous to the Magnus effect. Qualitative effects of the incoming magnetic field orientation, the strength of the magnetization, and the incoming wind speed are investigated as well.

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