Precise measurement of neutron star spins with neutron star-black hole mergers

The precise measurement of neutron star (NS) spins can provide important insight into the formation and evolution of these systems. While traditional methods of NS spin measurement rely on pulsar observations, gravitational wave detections offer a complementary avenue. However, determining component spins with gravitational waves is hindered by the small dimensionless spins of the NS and the degeneracy in the mass and spin parameters. This degeneracy can be addressed by the inclusion of higher-order modes in the waveform, which are important for asymmetric systems that are not face-on. The talk focuses on the suitability of neutron star-black hole mergers, which are naturally asymmetric, for precise NS spin measurement. We explore the effects of the black hole masses and spins, higher-mode content, inclination angle, and detector sensitivity on the measurement of NS spin. We find that networks with next-generation observatories like the Cosmic Explorer and the Einstein Telescope can distinguish NS dimensionless spin of 0.04 (0.1) from zero at 1-σ confidence for events at ∼200 (∼900) Mpc. Networks with A+ and A# detectors achieve similar distinction at ∼20 (∼50) Mpc and ∼40 (∼110) Mpc, respectively.