All-sky search for long-duration gravitational-wave transients in the first part of the fourth LIGO-Virgo-KAGRA Observing run

TL;DR

This paper reports an all-sky search for long-duration gravitational-wave transients during the first part of the O4 LIGO-Virgo-KAGRA run, setting new sensitivity limits and demonstrating improved detection capabilities for astrophysical signals lasting 1-1000 seconds.

Contribution

The study introduces an enhanced unmodeled search pipeline for long-duration GWs, achieving 30% better sensitivity limits compared to previous runs.

Findings

No significant GW detections were made.

Sensitivity limits improved by ~30% over O3.

Demonstrated progress in search efficiency and pipeline performance.

Abstract

We present an all-sky search for long-duration gravitational waves (GWs) from the first part of the LIGO-Virgo-KAGRA fourth observing run (O4), called O4a and comprising data taken between 24 May 2023 and 16 January 2024. The GW signals targeted by this search are the so-called "long-duration" (> 1 s) transients expected from a variety of astrophysical processes, including non-axisymmetric deformations in magnetars or eccentric binary coalescences. We make minimal assumptions on the emitted GW waveforms in terms of morphologies and durations. Overall, our search targets signals with durations ~1-1000 s and frequency content in the range 16-2048 Hz. In the absence of significant detections, we report the sensitivity limits of our search in terms of root-sum-square signal amplitude (hrss) of reference waveforms. These limits improve upon the results from the third LIGO-Virgo-KAGRA observing run (O3) by about 30% on average. Moreover, this analysis demonstrates substantial progress in our ability to search for long-duration GW signals owing to enhancements in pipeline detection efficiencies. As detector sensitivities continue to advance and observational runs grow longer, unmodeled long-duration searches will increasingly be able to explore a range of compelling astrophysical scenarios involving neutron stars and black holes.