TITLE: GCN CIRCULAR NUMBER: 41817 SUBJECT: LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search DATE: 25/09/12 20:13:49 GMT FROM: Zsuzsa Marka at IceCube/Columbia University <zsuzsa@astro.columbia.edu> IceCube Collaboration (http://icecube.wisc.edu/) reports: We have performed a search for track-like muon neutrino candidate events detected by IceCube consistent with the sky localization of the low-significance gravitational-wave candidate event S250912s in a time range of 1000 seconds centered on the alert event time (2025-09-12 18:13:09 UTC to 2025-09-12 18:29:49 UTC) [1,2]. During this time period, IceCube was collecting good quality data. A single hypothesis test was conducted using 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 statistical significance estimation [3]. Two track-like events were found in spatial and temporal coincidence with the gravitational-wave candidate S250912s calculated from the map circulated in the S250912s-2-Preliminary notice. This represents an overall p-value of 0.00927 for the Bayesian search. The p-value measures the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not accounting for statistical trials from multiple GW events). 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 are shown below: dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(Bayesian) ------------------------------------------------------------------------------------- -276.12 284.52 44.13 16.11 0.0115 19.10 275.72 24.65 1.44 0.0530 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 individual p-value for the specific track event from this 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/41817. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...