Coalescing binary neutron stars

Abstract

The behavior of a coalescing neutron star system in the final phases before coalescence is described, and the initial conditions appropriate for hydrodynamic simulation of the final coalescence are examined. A language is developed for describing the internal structure of the stars in terms of the Roche-Riemann ellipsoids, which are the generalizations of the Roche solutions which include variable amounts of angular momentum and circulation. The evolution of several binaries are investigated for different initial conditions and viscosities, and the strong dependence of the structure on the amount of viscosity is shown. Results of examinations of the magnitude and source of viscosity showed that the most probable structure of the star is the irrotational Roche-Riemann ellipsoid, rather than the commonly assumed Roche ellipsoid.