Mass ejection from the merger of binary neutron stars

Numerical-relativity simulations for the merger of binary neutron stars are performed for a variety of equations of state (EOSs) and for a plausible range of the neutron-star mass, focusing primarily on the properties of the material ejected from the system. We find that a fraction of the material is ejected as a mildly relativistic and mildly anisotropic outflow with the typical and maximum velocities ∼0.15-0.25c and ∼0.5-0.8c (where c is the speed of light), respectively, and that the total ejected rest mass is in a wide range 10 ^-4-10^-2M_⊙, which depends strongly on the EOS, the total mass, and the mass ratio. The total kinetic energy ejected is also in a wide range between 1049 and 1051 ergs. The numerical results suggest that for a binary of canonical total mass 2.7M _⊙, the outflow could generate an electromagnetic signal observable by the planned telescopes through the production of heavy-element unstable nuclei via the r-process or through the formation of blast waves during the interaction with the interstellar matter, if the EOS and mass of the binary are favorable ones.