Stringent constraints on neutron-star radii from multimessenger observations and nuclear theory

TL;DR

This paper combines multimessenger observations and nuclear theory to tightly constrain neutron star radii, providing new insights into their structure and implications for neutron-star mergers.

Contribution

It introduces a method integrating gravitational-wave and electromagnetic data with nuclear theory to precisely estimate neutron star radii, improving previous constraints.

Findings

Neutron star radius for 1.4 solar masses is 11.0^{+0.9}_{-0.6} km.

Neutron stars are unlikely to be disrupted in neutron-star black-hole mergers.

The approach constrains the equation of state of dense nuclear matter.

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 stringent constraints on neutron-star radii 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 $1.4\,\rm{M}_\odot$ neutron star is $R_{1.4\,\mathrm{M}_\odot} = 11.0^{+0.9}_{-0.6}~{\rm km}$ (90% credible interval). Using this constraint, we show that neutron stars are unlikely to be disrupted in neutron-star black-hole mergers; subsequently, such events will not produce observable electromagnetic emission.