Constraints on the Neutron Star Equation of State from GW170817

Observations of neutron stars provide one of the best ways of probing the ultra-dense matter equation of state (EOS). While X-ray measurements of the neutron star radius have provided some promising constraints on the EOS, uncertainties remain at high densities. Detections of gravitational waves from a binary neutron star (BNS) merger offer an exciting, complementary approach to constraining the EOS. In this talk, I will discuss what we have already learned about the EOS from a year of studying the first observed BNS merger, GW170817. In particular, I will explore the surprising relationship that has been discovered between the binary tidal deformability and the radius, which renders GW170817 a direct probe of the neutron star radius. I will compare the radius constraints from GW170817 to existing radii measurements from X-ray observations and discuss the implications for the EOS. I will also review new constraints on the maximum mass that have been inferred from GW170817. Finally, I will comment on the importance of disentangling thermal effects from the cold EOS in future analyses of gravitational waves.