Relativistic g-modes in rapidly rotating neutron stars

TL;DR

This paper investigates relativistic g-modes in rapidly rotating neutron stars using the Cowling approximation, revealing qualitative agreement with Newtonian results and advancing understanding of oscillation modes in relativistic stellar models.

Contribution

First study of relativistic g-modes in rotating neutron stars, incorporating composition gradients and buoyancy effects within a general relativistic framework.

Findings

Qualitative agreement with Newtonian g-mode behavior

Identification of the interplay between buoyant and Coriolis forces

Insights into the onset of CFS-unstable g-modes in relativistic stars

Abstract

We study the g-modes of fast rotating stratified neutron stars in the general relativistic Cowling approximation, where we neglect metric perturbations and where the background models take into account the buoyant force due to composition gradients. This is the first paper studying this problem in a general relativistic framework. In a recent paper by Passamonti et al.(2009), a similar study was performed within the Newtonian framework, where the authors presented results about the onset of CFS-unstable g-modes and the close connection between inertial- and gravity-modes for sufficiently high rotation rates and small composition gradients. This correlation arises from the interplay between the buoyant force which is the restoring force for g-modes and the Coriolis force which is responsible for the existence of inertial modes. In our relativistic treatment of the problem, we find an excellent qualitatively agreement with respect to the Newtonian results.