  General relativistic simulations of black hole-neutron star mergers have
currently been limited to low-mass black holes (less than 7 solar mass), even
though population synthesis models indicate that a majority of mergers might
involve more massive black holes (10 solar mass or more). We present the first
general relativistic simulations of black hole-neutron star mergers with 10
solar mass black holes. For massive black holes, the tidal forces acting on the
neutron star are usually too weak to disrupt the star before it reaches the
innermost stable circular orbit of the black hole. Varying the spin of the
black hole in the range a/M = 0.5-0.9, we find that mergers result in the
disruption of the star and the formation of a massive accretion disk only for
large spins a/M>0.7-0.9. From these results, we obtain updated constraints on
the ability of BHNS mergers to be the progenitors of short gamma-ray bursts as
a function of the mass and spin of the black hole. We also discuss the
dependence of the gravitational wave signal on the black hole parameters, and
provide waveforms and spectra from simulations beginning 7-8 orbits before
merger.
