Merging neutron stars: asymmetric systems

We present the results of 3D, Newtonian hydrodynamic calculations of the la st stages of the inspiral and the final coalescence of neutron star binary systems. Our focus is on slightly asymmetric systems, where the asymmetry s tems from either different masses (1.3 and 1.4 M.) or spins of both compone nts. Almost immediately after contact a fast rotating, very massive central object forms. All calculations exhibit baryonic masses above 2.3 Mo, thus based on our calculations it is not possible to decide on the fate of the c entral core of the merged configuration. It might collapse immediately to a black hole, but also the creation of a supermassive neutron star with simi lar to 2.8 M. Mo Cannot firmly be excluded. Depending on the asymmetry of t he system the central object receives a kick of several hundred kilometers per second. Different spins of both components do not jeopardize the format ion of (to within numerical resolution) baryon free funnels above the poles of the central objects. In the case of different masses the less massive c omponents get disrupted and engulf the more massive companions that stay ra ther unaffected by the collision. The amount of ejected material is in a si milar range as for symmetric systems and could contribute substantially to the enrichment of the Galaxy with heavy r-process elements. Test calculatio ns indicate that the amount of ejected material is basically determined by the high density behaviour of the nuclear equation of state. Test calculations for the hybrid artificial viscosity scheme that is used f or this work are given in the appendix.