Impact of three-nucleon forces on gravitational wave emission from neutron stars

TL;DR

This paper investigates how three-nucleon forces influence gravitational wave signals from neutron stars by analyzing their impact on the star's internal equation of state and resulting oscillation frequencies.

Contribution

It provides the first detailed analysis of the effects of three-nucleon interactions on neutron star oscillation modes and gravitational wave emission.

Findings

Three-nucleon forces significantly alter the equation of state stiffness.

The frequencies of neutron star oscillations are sensitive to three-nucleon interactions.

Gravitational wave patterns depend largely on the equation of state, not the star's mass.

Abstract

The detection of gravitational radiation, emitted in the aftermath of the excitation of neutron star quasi-normal modes, has the potential to provide unprecedented access to the properties of matter in the star interior, and shed new light on the dynamics of nuclear interactions at microscopic level. Of great importance, in this context, will be the sensitivity to themodelling of three-nucleon interactions, which are known to play a critical role in the high-density regime. We report the results of a calculation of the frequencies and damping times of the fundamental mode, carried out using the equation of state of Akmal, Pandharipande and Ravenhall as a baseline, and varying the strength of the isoscalar repulsive term the Urbana IX potential within a range consistent with multimessenger astrophysical observations. The results of our analysis indicate that repulsive three-nucleon interactions strongly affect the stiffness of the equation of state, which in turn determines the pattern of the gravitational radiation frequencies, largely independent of the mass of the source. The observational implications are also discussed.