The Memory Remains (Undetected): Updates from the Second LIGO/Virgo Gravitational-Wave Transient Catalog

TL;DR

This paper analyzes 50 gravitational-wave events from LIGO/Virgo to search for gravitational-wave memory effects, using advanced waveform models, and finds no significant evidence of memory, suggesting thousands more detections are needed for confirmation.

Contribution

It extends previous methods to analyze gravitational-wave memory in a larger set of events with complex waveforms, including extreme mass ratios and precession.

Findings

Bayes factors slightly favor memory hypothesis but are inconclusive.

Current data is insufficient to confirm gravitational-wave memory.

Approximately 2000 detections are needed to confidently detect memory.

Abstract

The LIGO and Virgo observatories have reported 39 new gravitational-wave detections during the first part of the third observation run, bringing the total to 50. Most of these new detections are consistent with binary black-hole coalescences, making them suitable targets to search for gravitational-wave memory, a non-linear effect of general relativity. We extend a method developed in previous publications to analyse these events to determine a Bayes factor comparing the memory hypothesis to the no-memory hypothesis. Specifically, we calculate Bayes factors using two waveform models with higher-order modes that allow us to analyse events with extreme mass ratios and precessing spins, both of which have not been possible before. Depending on the waveform model we find a combined $\ln \mathrm{BF}_{\mathrm{mem}} = 0.024$ or $\ln \mathrm{BF}_{\mathrm{mem}} = 0.049$ in favour of memory. This result is consistent with recent predictions that indicate $\mathcal{O}(2000)$ binary black-hole detections will be required to confidently establish the presence or absence of memory.