A search of the Orion spur for continuous gravitational waves using a "loosely coherent" algorithm on data from LIGO interferometers

TL;DR

This study conducted a wideband search for continuous gravitational waves from neutron stars in the Orion spur using a multi-stage, loosely coherent algorithm on LIGO data, setting upper limits on wave amplitudes without detecting signals.

Contribution

It introduces a multi-stage, loosely coherent search method that improves sensitivity in detecting continuous gravitational waves from isolated neutron stars.

Findings

No gravitational wave signals detected.

Set upper limits on strain amplitudes, as low as 6.3×10⁻²⁵ at 169 Hz.

Enhanced search depth compared to previous methods.

Abstract

We report results of a wideband search for periodic gravitational waves from isolated neutron stars within the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational waves interact very weakly with matter, the search is unimpeded by dust and concentrations of stars. One search disk (A) is $6.87^\circ$ in diameter and centered on $20^\textrm{h}10^\textrm{m}54.71^\textrm{s}+33^\circ33'25.29"$, and the other (B) is $7.45^\circ$ in diameter and centered on $8^\textrm{h}35^\textrm{m}20.61^\textrm{s}-46^\circ49'25.151"$. We explored the frequency range of 50-1500 Hz and frequency derivative from $0$ to $-5\times 10^{-9}$ Hz/s. A multi-stage, loosely coherent search program allowed probing more deeply than before in these two regions, while increasing coherence length with every stage. Rigorous followup parameters have winnowed initial coincidence set to only 70 candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolated gravitational wave emitter, and 95% confidence level upper limits were placed on continuous-wave strain amplitudes. Near $169$ Hz we achieve our lowest 95% CL upper limit on worst-case linearly polarized strain amplitude $h_0$ of $6.3\times 10^{-25}$, while at the high end of our frequency range we achieve a worst-case upper limit of $3.4\times 10^{-24}$ for all polarizations and sky locations.