Magnetically Arrested Circumbinary Accretion Flows

Abstract: Binary systems with comparable masses and a surrounding accretion disk can accrete gas through spiral accretion streams penetrating the central cavity formed by tidal interactions. Using three-dimensional Newtonian magnetohydrodynamics simulations, we investigate the possibility of a magnetically arrested accretion flow through the cavity. Rather than solely continuously feeding the binary through spiral accretion streams, the accretion is regulated by the strong magnetic field inside the cavity. Transport of mass and angular momentum onto the binary then proceeds largely periodically in magnetic flux eruption episodes. The ejected flux tubes carry angular momentum outwards and away from the binary, inject hot plasma into the disk and can launch flares. This likely intermittent scenario could have potential implications for the emission signatures of supermassive black hole binaries, and shed light onto the role magnetic fields play in the binary's orbital evolution.