Constraints on the symmetry energy from neutron star observations

TL;DR

This paper investigates how neutron star observations can constrain the nuclear symmetry energy parameter, particularly its slope at saturation density, by modeling various neutron star phenomena and comparing with observational data.

Contribution

The study introduces a consistent model linking neutron star observables to nuclear matter parameters, providing astrophysical constraints on the symmetry energy slope $L$.

Findings

Models predict $L<70$ MeV consistent with observations.

Neutron star oscillation frequencies help constrain nuclear matter properties.

Astrophysical data complement terrestrial experiments in nuclear physics.

Abstract

The modeling of many neutron star observables incorporates the microphysics of both the stellar crust and core, which is tied intimately to the properties of the nuclear matter equation of state (EoS). We explore the predictions of such models over the range of experimentally constrained nuclear matter parameters, focusing on the slope of the symmetry energy at nuclear saturation density $L$. We use a consistent model of the composition and EoS of neutron star crust and core matter to model the binding energy of pulsar B of the double pulsar system J0737-3039, the frequencies of torsional oscillations of the neutron star crust and the instability region for r-modes in the neutron star core damped by electron-electron viscosity at the crust-core interface. By confronting these models with observations, we illustrate the potential of astrophysical observables to offer constraints on poorly known nuclear matter parameters complementary to terrestrial experiments, and demonstrate that our models consistently predict $L<70$ MeV.