Fast Rotating Neutron Stars: Oscillations and Instabilities

TL;DR

This paper reviews recent research on oscillations and instabilities of fast rotating neutron stars, deriving equations for non-axisymmetric modes, and proposing universal relations useful for gravitational wave analysis.

Contribution

It introduces a new set of time evolution equations for non-axisymmetric oscillations in full general relativity and proposes universal relations for neutron star properties.

Findings

Accurate frequency extraction of non-axisymmetric modes up to the Kepler limit.

Universal relations independent of the equation of state.

Demonstration of Bayesian analysis for gravitational wave data.

Abstract

In this review article, we present the main results from our most recent research concerning the oscillations of fast rotating neutron stars. We derive a set of time evolution equations for the investigation of non-axisymmetric oscillations of rapidly rotating compact objects in full general relativity, taking into account the contribution of a dynamic spacetime. Using our code, which features high accuracy at comparably low computational expense, we are able to extract the frequencies of non-axisymmetric modes of compact objects with rotation rates up to the Kepler limit. We propose various universal relations combining bulk properties of isolated neutron stars as well as of binary systems before and after merger; these relations are independent of the true equation of state and may serve as a valuable tool for gravitational wave asteroseismology. We also present an introductory example using a Bayesian analysis.