High-resolution magnetohydrodynamics simulation of black hole-neutron
  star merger: Mass ejection and short gamma-ray burst
  We report results of a high-resolution numerical-relativity simulation for
the merger of black hole-magnetized neutron star binaries on Japanese
supercomputer "K". We focus on a binary that is subject to tidal disruption and
subsequent formation of a massive accretion torus. We find the launch of
thermally driven torus wind, subsequent formation of a funnel wall above the
torus and a magnetosphere with collimated poloidal magnetic field, and high
Blandford-Znajek luminosity. We show for the first time this picture in a
self-consistent simulation. The turbulence-like motion induced by the
non-axisymmetric magnetorotational instability as well as the Kelvin-Helmholtz
instability inside the accretion torus works as an agent to drive the mass
accretion and converts the accretion energy to thermal energy, which results in
the generation of a strong wind. By an in-depth resolution study, we reveal
that high resolution is essential to draw such a picture. We also discuss the
implication for the r-process nucleosynthesis, the radioactively-powered
transient emission, and short gamma-ray bursts.
