Continuous gravitational waves from thermal mountains on accreting neutron stars: effect of the nuclear pasta phase

TL;DR

This paper explores how nuclear pasta phases in neutron stars significantly enhance the quadrupole moment, increasing the potential for detectable continuous gravitational waves from accreting neutron stars.

Contribution

It demonstrates that nuclear pasta can increase the quadrupole moment by up to two orders of magnitude, impacting gravitational wave detectability and advancing understanding of neutron star crust properties.

Findings

Quadrupole moment can be up to 100 times larger due to nuclear pasta.

Predicted gravitational wave signals are above detector sensitivity thresholds.

Nuclear pasta properties influence the maximum shear strain and gravitational wave emission.

Abstract

As density increases, the shape of nuclei transitions to non-spherical ``nuclear pasta" structures. The physical properties of the nuclear pasta, such as thermal conductivity and elasticity, have implications for detecting continuous gravitational waves from a rapidly rotating neutron star. In this work, we investigate the effect of the nuclear pasta on the quadruple moment, and find out that, compared with previous work, the quadrupole moment contributing to continuous gravitational-wave radiation can be up to two orders of magnitude larger. We also discuss the relationship between the quadruple moment and the maximum shear strain. Considering the properties of nuclear pasta, we study the detectability of known accreting neutron stars and compare predicted results to the detectable amplitude limits. These sources are well above the sensitivity curves for Cosmic Explorer and Einstein Telescope detectors. Our work advances the understanding of the properties of nuclear pasta and a possible mechanism for continuous gravitational waves.