Imprints of the nuclear symmetry energy on gravitational waves from the axial w-modes of neutron stars

TL;DR

This study investigates how the nuclear symmetry energy influences the axial w-mode frequencies and damping times of neutron stars, revealing significant effects and universal behaviors related to neutron star compactness.

Contribution

It demonstrates the impact of the nuclear symmetry energy on gravitational wave modes of neutron stars using EOS constrained by recent nuclear data, and explores universal scaling behaviors.

Findings

Density dependence of symmetry energy affects mode frequencies and damping times.

Universal scaling of eigen-frequencies with neutron star compactness confirmed.

The $w_{II}$-mode exists only for stars with compactness ≥ 0.1078, regardless of EOS.

Abstract

The eigen-frequencies of the axial w-modes of oscillating neutron stars are studied using the continued fraction method with an Equation of State (EOS) partially constrained by the recent terrestrial nuclear laboratory data. It is shown that the density dependence of the nuclear symmetry energy $E_{sym}(\rho)$ affects significantly both the frequencies and the damping times of these modes. Besides confirming the previously found universal behavior of the mass-scaled eigen-frequencies as functions of the compactness of neutron stars, we explored several alternative universal scaling functions. Moreover, the $w_{II}$-mode is found to exist only for neutron stars having a compactness of $M/R\geq 0.1078$ independent of the EOS used.