# GCN Circular 35125

**Subject**

LIGO/Virgo/KAGRA S231119u: One counterpart neutrino candidate from IceCube neutrino searches

**Date**

2023-11-19T15:31:29Z (16 days ago)

**From**

Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>

**Via**

Web form

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IceCube Collaboration (http://icecube.wisc.edu/) reports:
Searches for track-like muon neutrino events detected by IceCube consistent with the sky localization of gravitational-wave candidate S231119u in a time range of 1000 seconds centered on the alert event time (2023-11-19 07:44:28.000 UTC to 2023-11-19 08:01:08.000 UTC) have been performed [1,2]. During this time period IceCube was collecting good quality data. Two hypothesis tests were conducted. The first search is a maximum likelihood analysis which searches for a generic point-like neutrino source coincident with the given GW skymap. The second 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].
One track-like event is found in spatial and temporal coincidence with the gravitational-wave candidate S231119u calculated from the map circulated in the 3-Initial notice. This represents an overall p-value of 0.0061 from the generic transient search and an overall p-value of 0.44 for the Bayesian search. These p-values measure the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not trials corrected for multiple GW events). The most probable multi-messenger source direction based on the neutrinos and GW skymap is RA 237.39, Dec -35.69 degrees.
The reported p-values can differ due to the estimated distance of the GW candidate. The distance is used as a prior in the Bayesian binary merger search, while it is not taken into account in the generic transient point-like source search. 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.
Properties of the coincident events are shown below.
dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(generic transient) p-value(Bayesian)
-----------------------------------------------------------------------------------------------------
-286.38 237.38 -35.65 0.43 0.006 null
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
```