Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory
Capano, C., Tews, I., Brown, S., Margalit, B., De, S., Kumar, S., Brown, D., Krishnan, B., Reddy, S.
Abstract
The properties of neutron stars are determined by the nature of the matter that they contain. These properties can be constrained by measurements of the star's size. We obtain the most stringent constraints on neutron-star radii to date by combining multimessenger observations of the binary neutron-star merger GW170817 with nuclear theory that best accounts for density-dependent uncertainties in the equation of state. We construct equations of state constrained by chiral effective field theory and marginalize over these using the gravitational-wave observations. Combining this with the electromagnetic observations of the merger remnant that imply the presence of a short-lived hyper-massive neutron star, we find that the radius of a $1.4M_\odot$ neutron star is $R_{1.4M_{\odot}} = 11.0^{+0.9}_{-0.6}~{\rm km}$ ($90\%$ credible interval). This constraint has important implications for dense-matter physics and for astrophysics.