Caltech/JPL Association for Gravitational-Wave Research Seminar

Information about the neutron-star equation of state is encoded in the gravitational waves emitted in the inspiral and coalescence of double neutron stars and neutron star-black hole (NS-BH) binaries. A stiff equation of state (EOS) has larger pressure at a given density, and yields a neutron star with larger radius, a star on which the tidal force of its companion is much larger. By deforming the stars, the tidal interaction takes energy from their orbit: The rate of energy loss for binaries with neutron stars is thus faster than for black-hole binaries, their inspiral waveform moves more quickly to higher frequencies, and they coalesce sooner. The departure of the waveform from that of two spinless black holes is almost entirely determined by the tidal deformability of the neutron star and that, in turn, is very nearly determined by the neutron star radius. Using hundreds of simulations that systematically vary the EOS and, for NS-BH binaries, the mass ratio, neutron star mass, and aligned spin of the black hole, we estimate the accuracy with with gravitational-wave observations can measure the NS deformability and thereby provide a model-indendent constraint on the the EOS of cold matter above nuclear density.