Paper detail

High Resolution Calculations of Merging Neutron Stars I: Model Description and Hydrodynamic Evolution

We present the results of 3D, high-resolution calculations of neutron star mergers. Using Newtonian gravity, but adding the forces from the emission of gravitational waves, we solve the hydrodynamics equations using the smoothed particle hydrodynamics method. The microscopic properties of the neutron star matter are described in terms of a new nuclear equation of state (EOS) based on the tables of Shen et al. (1998). The effects of neutrino emission of all flavours are accounted for. The new EOS is noticeably stiffer than the Lattimer-Swesty-EOS used in previous investigations. We find in general somewhat lower temperatures than previous investigations. This allows a substantial fraction of heavy nuclei to be present even in the inner parts of the torus that forms around the central object and yields important contributions to the neutrino opacity. The central object shows a rapid differential rotation with periods of $\sim$ 2ms, which we suspect to stabilize the central object on (at least) the simulation time scale against gravitational collapse. The differential rotation could wind up initial magnetic fields to $\sim 10^17$ G.