GCN Circular 33850

IceCube Collaboration (http://icecube.wisc.edu/) reports:

A search for track-like muon neutrino events detected by IceCube consistent with the sky localization of gravitational-wave candidate S230522a in a time range of 1000 seconds centered on the alert event time (2023-05-22 09:29:45.000 UTC to 2023-05-22 09:46:25.000 UTC) have been performed [1,2]. During this time period IceCube was collecting good quality data. The search is a maximum likelihood analysis which searches for a generic point-like neutrino source coincident with the given GW skymap.  

2 track-like event(s) are found in spatial and temporal coincidence with the gravitational-wave candidate S230522a calculated from the map circulated in the 2-Preliminary notice. This represents an overall p-value of 0.04 (1.8 sigma).  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 78.93, dec -37.54 degrees. The false alarm rate of these coincidences can be obtained by multiplying the p-values with their corresponding GW trigger rates. 

Properties of the coincident events are shown below.

 dt     ra         dec    Angular Uncertainty(deg)  p-value(generic transient) p-value(Bayesian)
-----------------------------------------------------------------------------------------------------
-152.13           78.98           -37.59           0.43           0.04           n/a
73.08              127.79            -8.33           0.43           0.09           n/a

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