All-sky LIGO Search for Periodic Gravitational Waves in the Early S5 Data

TL;DR

This paper reports an all-sky search for periodic gravitational waves using LIGO data from 2008, setting upper limits on neutron star emissions and significantly improving sensitivity over previous searches.

Contribution

It introduces a semi-coherent PowerFlux method for all-sky gravitational wave searches, enhancing sensitivity and spatial volume coverage compared to prior efforts.

Findings

No evidence of periodic gravitational waves was found.

Strain limits below 1E-24 achieved over a 200-Hz band.

Sensitivity increased the sampled volume by a factor of about 100.

Abstract

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50--1100 Hz and with the frequency's time derivative in the range -5.0E-9 Hz/s to zero. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semi-coherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 1.E-24 are obtained over a 200-Hz band, and the sensitivity improvement over previous searches increases the spatial volume sampled by an average factor of about 100 over the entire search band. For a neutron star with nominal equatorial ellipticity of 1.0E-6, the search is sensitive to distances as great as 500 pc--a range that could encompass many undiscovered neutron stars, albeit only a tiny fraction of which would likely be rotating fast enough to be accessible to LIGO. This ellipticity is at the upper range thought to be sustainable by conventional neutron stars and well below the maximum sustainable by a strange quark star.