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GCN Circular 34838

LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
2023-10-19T02:06:25Z (a month ago)
Erik Blaufuss at University of Maryland, College Park <>
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IceCube Collaboration ( reports:

We have performed a search for track-like muon neutrino events detected by IceCube consistent with the sky localization of the low-significance gravitational-wave candidate event S231018cb in a time range of 1000 seconds centered on the alert event time (2023-10-18T23:40:06 UTC to 2023-10-18T23:56:46 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].  

One track-like event is found in spatial and temporal coincidence with the gravitational-wave 
Candidate S231018cb calculated from the map circulated in the S231018cb-2-Preliminary notice. This represents an overall p-value of 0.003 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 and at

Properties of the coincident events are shown below:

 dt(s)     RA(deg)       Dec(deg)    Angular uncertainty(deg)  p-value(Bayesian)
-24.13   170.53         +11.11           0.53                                  0.0031

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

[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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