Merger of black hole–neutron star binaries in full general relativity

We present our latest results for simulation for merger of black hole (BH)-neutron star (NS) binaries in full general relativity which is performed preparing a quasicircular state as initial condition. The BH is modeled by a moving puncture with no spin and the NS by the \Γ-law equation of state with \Γ=2 and corotating velocity field as a first step. The mass of the BH is chosen to be \≈ 3.2 M\ or 4.0M\, and the rest-mass of the NS \≈ 1.4 M\ with relatively large radius of the NS \≈ 13--14 km. The NS is tidally disrupted near the innermost stable orbit but \~ 80--90% of the material is swallowed into the BH and resulting disk mass is not very large as \~ 0.3M\ even for small BH mass \~ 3.2M\. The result indicates that the system of a BH and a massive disk of \~ M\ is not formed from nonspinning BH-NS binaries irrespective of BH mass, although a disk of mass \~ 0.1M\ is a possible outcome for this relatively small BH mass range as \~ 3--4M\. Our results indicate that the merger of low-mass BH and NS may form a central engine of short-gamma-ray bursts.