Inferring neutron star properties from GW170817 with universal relations

Because all neutron stars share a common equation of state, the tidal deformability measurement from the binary merger GW170817 has implications for the properties of other neutron-star systems. Using equation-of-state insensitive relations between observables like moment of inertia, tidal deformability and stellar compactness, we derive constraints on these properties as a function of neutron-star mass. The constraints allow us to make virtually model-independent inferences for the double pulsar moment of inertia, the radii of X-ray bursters, and millisecond pulsar spins. The gravitational-wave based estimates can be compared or combined with electromagnetic measurements, where available, to test the universality of the equation of state and enhance probes of neutron-star structure.