Characteristics of the nuclear equation of state inferred from the binary neutron star merger*

The historical first detection of a binary neutron star (BNS) merger by the LIGO-Virgo Collaboration has provided fundamental new insights into the nature of dense neutron-rich nuclear matter. By using a set of realistic models of the equation of state (EOS) that yield an accurate description of the properties of finite nuclei, support neutron stars of two solar masses, and provide a Lorentz covariant extrapolation to dense matter, we confront their predictions against the measured tidal deformability from the BNS merger. Since the gravitational-wave signal is sensitive to the underlying EOS, limits on the tidal deformability inferred from the observation translate into constraints on the bulk properties of the EOS of neutron-rich matter, such as the density dependence of the nuclear symmetry energy. In particular, we infer the density slope of the symmetry energy to be $L \lesssim 80$ MeV, which is closely related to the pressure of pure neutron matter at saturation density. Given the sensitivity of the laboratory observable, the neutron-skin thickness of $^{208}$Pb, to the pressure of neutron-rich matter we infer a corresponding upper limit to be about $R_{\rm skin}^{208} \lesssim 0.25$ fm. Similarly, this measurement translates into an upper constraint on the astrophysical observable of a neutron-star radius of a 1.4 solar mass neutron star, $R_{1.4} \lesssim 13.76$ km. We will further discuss observational implications of future nuclear experiments on the dynamics of BNS merger and properties of the neutron star core.