Gravitational waves from the r-modes of rapidly rotating neutron stars

TL;DR

Rapidly rotating neutron stars with unstable r-modes can emit detectable gravitational waves, potentially observable by advanced LIGO, with implications for astrophysics and cosmology.

Contribution

This paper reviews recent developments in understanding r-mode instabilities in neutron stars and their potential as sources of detectable gravitational waves.

Findings

Neutron stars may emit gravitational waves detectable by LIGO.

R-mode instability could spin down newborn neutron stars within a year.

A cosmological background of such gravitational waves might be observable.

Abstract

Since the last Amaldi meeting in 1997 we have learned that the r-modes of rapidly rotating neutron stars are unstable to gravitational radiation reaction in astrophysically realistic conditions. Newborn neutron stars rotating more rapidly than about 100Hz may spin down to that frequency during up to one year after the supernova that gives them birth, emitting gravitational waves which might be detectable by the enhanced LIGO interferometers at a distance which includes several supernovae per year. A cosmological background of these events may be detectable by advanced LIGO. The spins (about 300Hz) of neutron stars in low-mass x-ray binaries may also be due to the r-mode instability (under different conditions), and some of these systems in our galaxy may also produce detectable gravitational waves--see the review by G. Ushomirsky in this volume. Much work is in progress on developing our understanding of r-mode astrophysics to refine the early, optimistic estimates of the detectability of the gravitational waves.