Gravity wave signals from relativistic calculations of binary neutron star coalescence

Abstract

This thesis describes the design, testing, and implementation of a Lagrangian, post-Newtonian, smoothed particle hydrodynamics code used to study the gravitational wave signature produced by coalescing neutron star binary systems. Additionally, we have studied the properties of remnants which may be formed during the merger process. We have introduced a hybrid post-Newtonian formalism, which treats lowest order 1PN relativistic terms at a reduced strength, to make the problem numerically tractable, while treating the gravitational radiation reaction, which is the lowest order dissipative term in general relativity, at full strength. We compare the results of calculations with and without 1PN effects for initially synchronized binary systems, for neutron stars with polytropic equations of state, finding that relativistic corrections play an important role in the dynamical stability of such sytems and the resulting gravitational wave forms. Relativistic corrections also suppress mass shedding in these systems. Studies of initially irrotational binary systems demonstrated that our results are independent of the numerical resolution of the calculations. The power spectrum of the gravitational radiation produced during a merger is found to yield important information about the neutron star equation of state, the binary mass ratio, and other physical parameters of the system.