Black hole-neutron star mergers for 10 M_☉ black holes

Abstract

General relativistic simulations of black hole-neutron star mergers have currently been limited to low-mass black holes (M_(BH)≤7  M_⊙), even though population synthesis models indicate that a majority of mergers might involve more massive black holes (M_(BH)≥10  M_⊙). We present the first general relativistic simulations of black hole-neutron star mergers with M_(BH_∼10  M_⊙. 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 α_(BH)/M_(BH)=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 α_(BH)/M_(BH)≥0.7–0.9. From these results, we obtain updated constraints on the ability of black hole-neutron star 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 the merger.

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