Search for gravitational waves from five low mass X-ray binaries in the second Advanced LIGO observing run with an improved hidden Markov model

TL;DR

This paper reports a search for continuous gravitational waves from five low-mass X-ray binaries using Advanced LIGO data, employing an improved hidden Markov model to track spin wandering and orbital phase, resulting in candidate signals for future follow-up.

Contribution

The study introduces an enhanced hidden Markov model-based search algorithm for gravitational waves from low-mass X-ray binaries, improving detection prospects.

Findings

Identified several low-significance candidates consistent with false-alarm probability.

Demonstrated the effectiveness of the improved hidden Markov model in tracking spin wandering.

Candidates will be investigated further in future observing runs.

Abstract

Low mass X-ray binaries are prime targets for continuous gravitational wave searches by ground-based interferometers. Results are presented from a search for five low-mass X-ray binaries whose spin frequencies and orbital elements are measured accurately from X-ray pulsations: HETE J1900.1-2455, IGR J00291+5934, SAX J1808.4-3658, XTE J0929-314, and XTE J1814-338. Data are analysed from Observing Run 2 of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). The search algorithm uses a hidden Markov model to track spin wandering, the $\mathcal{J}$-statistic maximum likelihood matched filter to track orbital phase, and a suite of five vetoes to reject artefacts from non-Gaussian noise. The search yields a number of low-significance, above threshold candidates consistent with the selected false-alarm probability. The candidates will be followed up in subsequent observing runs.