Non-adiabatic oscillations of compact stars in general relativity

TL;DR

This paper introduces a formalism for analyzing non-adiabatic, non-radial oscillations of non-rotating compact stars in general relativity, accounting for thermal diffusion effects on oscillation modes and damping times.

Contribution

The authors develop a new formalism that incorporates thermal diffusion into the study of stellar oscillations within general relativity, extending previous adiabatic models.

Findings

Thermal diffusion significantly alters p- and g-mode frequencies.

Damping times are reduced by over two orders of magnitude due to thermal effects.

Fundamental mode frequencies remain largely unaffected by thermal diffusion.

Abstract

We have developed a formalism to study non-adiabatic, non-radial oscillations of non-rotating compact stars in the frequency domain, including the effects of thermal diffusion in the framework of general relativistic perturbation theory. When a general equation of state depending on temperature is used, the perturbations of the fluid result in heat flux which is coupled with the spacetime geometry through the Einstein field equations. Our results show that the frequency of the first pressure (p) and gravity (g) oscillation modes is significantly affected by thermal diffusion, while that of the fundamental (f) mode is basically unaltered due to the global nature of that oscillation. The damping time of the oscillations is generally much smaller than in the adiabatic case (more than two orders of magnitude for the p- and g-modes) reflecting the effect of thermal dissipation. Both the isothermal and adiabatic limits are recovered in our treatment and we study in more detail the intermediate regime. Our formalism finds its natural astrophysical application in the study of the oscillation properties of newly born neutron stars, neutron stars with a deconfined quark core phase, or strange stars which are all promising sources of gravitational waves with frequencies in the band of the first generation and advanced ground-based interferometric detectors.