On the frequency band of the f-mode CFS instability

TL;DR

This paper investigates the frequencies of f-modes in rapidly rotating neutron stars using full general relativity simulations, revealing that relativity broadens the instability window and enhances detectability for gravitational wave detectors.

Contribution

It provides the first detailed analysis of f-mode frequencies in rotating neutron stars within full general relativity, identifying the impact on gravitational wave detection prospects.

Findings

Relativity widens the instability window for f-modes.

The frequency band for CFS instability extends into the optimal range for detectors.

General relativity significantly improves the chances of detecting gravitational waves from these stars.

Abstract

Rapidly rotating neutron stars can be unstable to the gravitational-wave-driven CFS mechanism if they have a neutral point in the spectrum of nonaxisymmetric f-modes. We investigate the frequencies of these modes in two sequences of uniformly rotating polytropes using nonlinear simulations in full general relativity, determine the approximate locations of the neutral points, and derive limits on the observable frequency band available to the instability in these sequences. We find that general relativity enhances the detectability of a CFS-unstable neutron star substantially, both by widening the instability window and enlarging the band into the optimal range for interferometric detectors like LIGO, VIRGO, and GEO-600.