Insights on Skyrme parameters from GW170817

TL;DR

This paper investigates how different Skyrme energy density functionals influence neutron star properties, especially tidal deformability, and identifies key nuclear matter parameters correlated with observable neutron star features.

Contribution

It introduces a comprehensive analysis of over 200 Skyrme functionals in neutron star modeling, highlighting correlations between nuclear matter parameters and neutron star observables.

Findings

Strong correlation between $\Lambda$ and $K_{sym}$ at saturation density.

Significant impact of crust EoS on neutron star radius predictions.

Correlation between $\Lambda$ and total pressure at twice saturation density.

Abstract

The binary neutron-star merger event, GW170817, has cast a new light on nuclear physics research. Using a neutron-star model that includes a crust equation of state (EoS), we calculate the properties of a 1.4 solar-mass neutron star. The model incorporates more than 200 Skyrme energy density functionals, which describe nuclear matter properties, in the outer liquid core region of the neutron star. We find a power-law relation between the neutron-star tidal deformability, $\Lambda$, and the neutron-star radius, R. Without an explicit crust EoS, the model predicts smaller R and the difference becomes significant for stars with large radii. To connect the neutron star properties with nuclear matter properties, we confront the predicted values for $\Lambda$, against the Taylor expansion coefficients of the Skyrme interactions. There is no pronounced correlation between Skyrme parameters in symmetric nuclear matter and neutron star properties. However, we find the strongest correlation between $\Lambda$ and $K_{sym}$, the curvature of the density dependence of the symmetry energy at saturation density. At twice the saturation density, our calculations show a strong correlation between $\Lambda$ and total pressure providing guidance to laboratory nucleus-nucleus collision experiments.