Coherent searches for periodic gravitational waves from unknown isolated sources and Scorpius X-1: results from the second LIGO science run

TL;DR

This paper reports the first broad-band, wide-parameter-space upper limits on periodic gravitational waves from unknown neutron stars and Scorpius X-1, using coherent search techniques on LIGO data, setting the stage for future more sensitive searches.

Contribution

It introduces the first broad-band, wide-parameter-space upper limits on gravitational waves using coherent search methods, applied to LIGO data for unknown neutron stars and Scorpius X-1.

Findings

Upper limits on gravitational wave strain range from 6.6E-23 to 1E-21 for isolated neutron stars.

Upper limits range from 1.7E-22 to 1.3E-21 for Scorpius X-1.

Methods establish a foundation for future hierarchical searches with more sensitive data.

Abstract

We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from the second LIGO science run. The first search is targeted at isolated, previously unknown neutron stars and covers the entire sky in the frequency band 160-728.8 Hz. The second search targets the accreting neutron star in the low-mass X-ray binary Scorpius X-1, covers the frequency bands 464-484 Hz and 604-624 Hz, and two binary orbit parameters. Both searches look for coincidences between the Livingston and Hanford 4-km interferometers. For isolated neutron stars our 95% confidence upper limits on the gravitational wave strain amplitude range from 6.6E-23 to 1E-21 across the frequency band; For Scorpius X-1 they range from 1.7E-22 to 1.3E-21 across the two 20-Hz frequency bands. The upper limits presented in this paper are the first broad-band wide parameter space upper limits on periodic gravitational waves using coherent search techniques. The methods developed here lay the foundations for upcoming hierarchical searches of more sensitive data which may detect astrophysical signals.