Gravitational Waves Detected by a Burst Search in LIGO/Virgo's Third Observing Run

TL;DR

This paper reports the detection of three new gravitational wave events from binary black hole mergers in LIGO/Virgo's third observing run, identified through a burst search method that does not rely on specific signal models.

Contribution

It demonstrates the effectiveness of a burst search algorithm, Coherent WaveBurst, in uncovering previously unreported BBH merger signals in GW data.

Findings

Detected 3 new BBH merger events with a combined significance of 3.6 sigma.

One event has a primary mass in the upper mass gap and a low mass ratio.

The new events are consistent with expected burst-only detection rates.

Abstract

Burst searches identify gravitational-wave (GW) signals in the detector data without use of a specific signal model, unlike the matched-filter searches that correlate data with simulated signal waveforms (templates). While matched filters are optimal for detection of known signals in the Gaussian noise, the burst searches can be more efficient in finding unusual events not covered by templates or those affected by non-Gaussian noise artifacts. Here, we report the detection of 3 gravitational wave signals that are uncovered by a burst search Coherent WaveBurst (cWB) optimized for the detection of binary black hole (BBH) mergers. They were found in the data from the LIGO/Virgo's third observing run (O3) with a combined significance of 3.6 $\sigma$. Each event appears to be a BBH merger not previously reported by the LIGO/Virgo's matched-filter searches. The most significant event has a reconstructed primary component in the upper mass gap ($m_1 = 70^{+36}_{-18}\,$M$_\odot$), and unusually low mass ratio ($m_2/m_1\sim0.3$), implying a dynamical or AGN origin. The 3 new events are consistent with the expected number of cWB-only detections in the O3 run ($4.8 \pm 2.1$), and belong to the stellar-mass binary population with the total masses in the $70-100$ M$_\odot$ range.