Hierarchical Hough all-sky search for periodic gravitational waves in LIGO S5 data

TL;DR

This paper introduces a hierarchical Hough transform pipeline for all-sky searches of continuous gravitational waves in LIGO S5 data, improving detection robustness and computational efficiency.

Contribution

It presents a novel two-step hierarchical Hough search method with coincidence analysis and veto strategies for enhanced gravitational wave detection.

Findings

Successful implementation of the hierarchical Hough pipeline

Improved sensitivity over previous all-sky searches

Effective veto strategies reduce false alarms

Abstract

We describe a new pipeline used to analyze the data from the fifth science run (S5) of the LIGO detectors to search for continuous gravitational waves from isolated spinning neutron stars. The method employed is based on the Hough transform, which is a semi-coherent, computationally efficient, and robust pattern recognition technique. The Hough transform is used to find signals in the time-frequency plane of the data whose frequency evolution fits the pattern produced by the Doppler shift imposed on the signal by the Earth's motion and the pulsar's spin-down during the observation period. The main differences with respect to previous Hough all-sky searches are described. These differences include the use of a two-step hierarchical Hough search, analysis of coincidences among the candidates produced in the first and second year of S5, and veto strategies based on a $\chi^2$ test.