Coupling of radial and non-radial oscillations of Neutron stars

TL;DR

This paper develops a formalism to study the coupling between radial and non-radial oscillations in neutron stars, aiming to understand their impact on gravitational wave signals and identify resonance phenomena.

Contribution

It introduces gauge-invariant quantities and equations for coupled perturbations, facilitating time domain analysis of neutron star oscillations.

Findings

Formalism for coupled oscillations developed

Potential resonance effects identified

Framework for gravitational wave signal analysis created

Abstract

This is a progress report on our study of the coupling of first-order radial and non-radial relativistic perturbations of a static spherical star. Our goal is to investigate the effects of this coupling on the gravitational wave signal of neutron stars. In particular, we are looking for the existence of resonances and parametric amplifications, changes in the damping time of non-radial oscillations, etc. To that end, we have developed a formalism that introduces gauge invariant quantities to describe the coupling. Their equations have the same structure as the equations for first-order non-radial perturbations plus some source terms, which makes them very appealing for time domain studies.