Search for gravitational waves from Scorpius X-1 with a hidden Markov model in O3 LIGO data with a corrected orbital ephemeris

TL;DR

This study conducted a semi-coherent search for gravitational waves from Scorpius X-1 in O3 LIGO data using an updated orbital ephemeris and a hidden Markov model, resulting in improved search efficiency but no detection.

Contribution

The paper introduces a corrected orbital ephemeris and applies a hidden Markov model to enhance the search for gravitational waves from Scorpius X-1, reducing the search domain and computational effort.

Findings

No gravitational wave evidence was detected in the 60-500 Hz band.

Upper limits on gravitational wave strain are consistent with previous results.

The corrected search domain is approximately three times smaller, improving search efficiency.

Abstract

Results are presented for a semi-coherent search for gravitational waves from the low-mass X-ray binary Scorpius X-1 in Observing Run 3 (O3) data from the Laser Interferometer Gravitational Wave Observatory, using an updated orbital parameter ephemeris and a hidden Markov model (HMM) to allow for spin wandering. The new orbital ephemeris corrects errors in previously published orbital measurements and implies a new search domain. This search domain does not overlap with the one used in the original Scorpius X-1 HMM O3 search. The corrected domain is approximately three times smaller by area in the $T_{\rm asc}$--$P$ plane than the original domain, where $T_{\rm asc}$ and $P$ denote the time of passage through the ascending node and the orbital period respectively, reducing the trials factor and computing time. No evidence is found for gravitational radiation in the search band from 60 Hz to 500 Hz. Upper limits are computed for the characteristic gravitational wave strain. They are consistent with the values from the original Scorpius X-1 HMM O3 search.