Numerical models of binary neutron star system mergers. II. Coalescing models with post-Newtonian radiation reaction forces

Using a grid-based staggered-mesh hydrodynamics code, we present the evolution of initially Newtonian equilibrium configurations of symmetric binary neutron star systems under the influence of a post-Newtonian gravitational radiation reaction potential. These simulations indicate that the time to merger for binaries with separations on the order of a few stellar radii is between 1/2 and 1 Keplerian period of the initial configuration. These results are in contrast to the larger timescales calculated from earlier smoothed particle hydrodynamics calculations that include quadrupolar-type radiation reaction forces. The implications of our studies are discussed in the context of observable effects on the gravitational waveforms expected to be observed by ground-based gravity-wave detectors such as the Laser Interferometer Gravitational-Wave Observatory and the restrictions placed on the choice of initial data for fully relativistic calculations.