TITLE: GCN CIRCULAR NUMBER: 39928 SUBJECT: LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search DATE: 25/03/29 16:53:25 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 S250329fl in a time range of 1000 seconds centered on the alert event time (2025-03-29T14:58:44.29 UTC to 2025-03-29T15:15:24.29 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 S250329fl calculated from the map circulated in the S250329fl-2-Preliminary notice. This represents an overall p-value of 5.05e-05 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 events are shown below:
dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(Bayesian) ------------------------------------------------------------------------------------- 390.16 279.03 -49.69 0.98 0.0000505 153.42 87.16 47.51 4.07 0.0915
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 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
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