Gravitational waves from hot young rapidly rotating neutron stars

TL;DR

This paper models gravitational waves emitted by young, rapidly rotating neutron stars due to r-mode instabilities, predicting detectable signals for current and future gravitational wave detectors and analyzing the stochastic background from neutron star formation.

Contribution

It provides a simple model of the neutron star r-mode instability evolution and predicts gravitational wave signals detectable by LIGO and VIRGO, including the stochastic background.

Findings

Neutron stars in Virgo could be detected with enhanced LIGO/VIRGO sensitivity.

The stochastic gravitational wave background from neutron star formation could be detectable by advanced LIGO.

The gravitational wave energy density from this background is about 10^-9 of the cosmological closure density.

Abstract

Gravitational radiation drives an instability in the r-modes of young rapidly rotating neutron stars. This instability is expected to carry away most of the angular momentum of the star by gravitational radiation emission, leaving a star rotating at about 100 Hz. In this paper we model in a simple way the development of the instability and evolution of the neutron star during the year-long spindown phase. This allows us to predict the general features of the resulting gravitational waveform. We show that a neutron star formed in the Virgo cluster could be detected by the LIGO and VIRGO gravitational wave detectors when they reach their ``enhanced'' level of sensitivity, with an amplitude signal-to-noise ratio that could be as large as about 8 if near-optimal data analysis techniques are developed. We also analyze the stochastic background of gravitational waves produced by the r-mode radiation from neutron-star formation throughout the universe. Assuming a substantial fraction of neutron stars are born with spin frequencies near their maximum values, this stochastic background is shown to have an energy density of about 10^-9 of the cosmological closure density, in the range 20 Hz to 1 kHz. This radiation should be detectable by ``advanced'' LIGO as well.