Search for coincidences between IceCube sub-TeV neutrinos and sub-threshold Gravitational Wave events in the LIGO-Virgo-KAGRA third observing run

Since the first direct detection of gravitational waves (GW) by the LIGO-Virgo-KAGRA detectors, the IceCube Neutrino Observatory has actively participated in identifying their neutrino counterparts. The sub-threshold GW alerts from the third observation run of LIGOVirgo-KAGRA, identified by both template-based searches and minimally modelled pipelines, have also been examined in follow-up analyses with TeV-PeV neutrinos, but no correlations were found. This work presents a systematic search for lower-energy neutrino emission from the sub-threshold GWs, utilising the archival all-flavour, sub-TeV neutrino sample from the IceCube Neutrino Observatory. From the public GW catalogues, we identify 103 promising candidates, comprising a mixture of compact binary mergers and GW burst triggers. After conducting a catalogue search to identify correlated sub-TeV neutrinos within a 1000 s time window, employing an unbinned maximum likelihood method, no significant coincidences are found. Hence, we report neutrino flux upper limits from the sub-threshold GW sources followed up in this analysis within sub-TeV neutrino energy.