GW170817: Joint Constraint on the Neutron Star Equation of State from Multimessenger Observations

Gravitational waves detected from the binary neutron star (NS) merger GW170817 constrained the NS equation of state by placing an upper bound on certain parameters, describing the binary’s tidal interactions. We show that the interpretation of the UV/optical/infrared counterpart of GW170817 with kilonova models, combined with new numerical-relativity results, imply a complementary lower bound on the tidal deformability parameter. The joint constraints tentatively rule out both extremely stiff and soft NS equations of state.