Insights on Skyrme parameters from GW170817

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, Λ, 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 Λ, 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 Λ and Ksym, 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 Λ and total pressure providing guidance to laboratory nucleus-nucleus collision experiments.

The Equation of State of Nuclear Matter: From Finite Nuclei to Neutron Stars

“…47 1.4 , in agreement with the work of Refs. [127,128]. We note, however, that a quadratic function (continuous) Λ 1.4 = 9922.02 − 1757.55R 1.4 + 79.91R 2 1.4 fits equally well the data.…”

“…[127] who found it to be of the form Λ 1.4 ∼ R 6 1.4 , and later by Tsang et al in Ref. [128] using a different set of EoS based again on Skyrme and relativistic mean-field models. In this work we find that the EoS data can be fitted assuming a power law (dashed line) of the form Λ 1.4 = 3.65 × 10 −5 R 6.…”

Nuclear Pairing Gaps and Neutron Star Cooling

“…The NS mass domain that we are interested in, is hardly affected by the structure of this low-density transition region and the crustal EOS: The choice of the crust model can influence the predictions of radius and related deformability to a small extent, of the order of 1% for the value of a 1.4-solar-mass NS, R 1.4 [31][32][33], which is negligible for our purpose. Even neglecting the crust completely, NS radius and deformability do not change dramatically [34].…”

Constraints on Skyrme equations of state from doubly magic nuclei, ab initio calculations of low-density neutron matter, and neutron stars

“…Once the TOV equations have been solved, and the energy density and pressure profiles are obtained, then one can integrate the differential equation needed to obtain the tidal deformability [13]. This TOV solver has been used successfully to connect neutron star properties to nuclear matter parameters in Skyrme interactions [33].…”