Effects of Magnetic Field Topology in Black Hole-Neutron Star Mergers: Long-Term Simulations

Mew-Bing Wan

Published 2016-06-29Version 1

We report long-term simulations of black hole-neutron star binary mergers where the neutron star possesses an asymmetric magnetic field dipole. Focusing on the scenario where the neutron star is tidally disrupted by the black hole, we track the evolution of the binary up to $\approx 100$ms after merger. We uncover more than one episode of thermally driven winds being launched along a funnel wall in all these cases beginning from $\approx 25$ms after merger. The emission rate of the second wind episode is found to increase with the degree of asymmetry. A large-scale poloidal magnetic field configuration is formed along the funnel wall accompanied by the generation of a large Poynting flux. The magnetic field in the accretion disk around the black hole remnant is amplified by the non-axisymmetric magneto-rotational instability. However, the asymmetry in the magnetic field leads to increased turbulence which causes the poloidal magnetic field in the accretion disk to grow largely in a non-linear manner.