LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches

A search for track-like muon neutrino events detected by IceCube consistent with the sky localization of the low-significance gravitational wave candidate S231025a in a time range of 1000 seconds centered on the alert event time (2023-10-25 03:03:04 UTC to 2023-10-25 03:19:44 UTC) has been performed [1,2]. During this time period IceCube was collecting good quality data. One hypothesis test was conducted for this low-significance gravitational wave event. The search uses a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the significance estimate [3]. Two track-like events are found in spatial and temporal coincidence with the gravitational-wave candidate S231025a calculated from the map circulated by LVK as S231025a-2-Preliminary. This represents an overall pre-trial p-value of 0.0010 for the Bayesian search. The reported p-value here does not account for any trials correction (multiple hypotheses testing). The false alarm rate of these coincidences can be obtained by multiplying the p-values with their corresponding GW trigger rates. Further details are available at https://gcn.nasa.gov/missions/icecube and at https://roc.icecube.wisc.edu/public/LvkNuTrackSearch. Properties of the coincident event(s) are shown below. dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(generic transient) p-value(Bayesian) ----------------------------------------------------------------------------------------------------- -331.09 226.87 -4.88 1.81 not applicable 0.0253 +284.41 240.49 -3.37 2.06 not applicable 0.0011 where: dt = Time of track event minus time of GW trigger (sec) Angular uncertainty = Angular uncertainty of track event: the radius of a circle representing 90% CL containment by area. p-value = the p-value for this specific track event from each search. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu [1] M. G. Aartsen et al 2020 ApJL 898 L10 [2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80 [3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017