{
  "eventId": "LIGO/Virgo/KAGRA S250918aw",
  "bibcode": "2025GCN.41867....1I",
  "subject": "LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search",
  "circularId": 41867,
  "createdOn": 1758203288757,
  "format": "text/plain",
  "submittedHow": "web",
  "submitter": "Zsuzsa Marka at IceCube/Columbia University <zsuzsa@astro.columbia.edu>",
  "body": "IceCube Collaboration (http://icecube.wisc.edu/) reports:\n\nWe 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 S250918aw in a time range of 1000 seconds centered on the alert event time (2025-09-18 07:55:35 UTC to 2025-09-18 08:12:15 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].  \n\nOne track-like event was found in spatial and temporal coincidence with the gravitational-wave candidate S250918aw calculated from the map circulated in the S250918aw-2-Preliminary notice. This represents an overall p-value of 0.00023 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). \n\nFurther details are available at https://gcn.nasa.gov/missions/icecube and at https://roc.icecube.wisc.edu/public/LvkNuTrackSearch.\n\nProperties of the coincident event are shown below:\n\n dt(s)     RA(deg)       Dec(deg)    Angular uncertainty(deg)  p-value(Bayesian)\n-------------------------------------------------------------------------------------\n-74.35 \t\t159.8 \t\t44.3 \t\t0.66 \t\t\t0.00023\n\n\nwhere:\ndt = Time of track event minus time of GW trigger (sec)\nAngular uncertainty = Angular uncertainty of track event: the radius of a circle \n     representing 90% CL containment by area.\np-value = the individual p-value for the specific track event from this search.\n\nThe 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\n\n[1] M. G. Aartsen et al 2020 ApJL 898 L10\n[2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80\n[3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017\n"
}