GCN Circular 35125

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