TITLE:   GCN CIRCULAR
NUMBER:  34107
SUBJECT: LIGO/Virgo/KAGRA low-significance gravitational wave candidate S230628aj: one counterpart neutrino candidate from IceCube neutrino searches
DATE:    23/06/28 18:26:22 GMT
FROM:    acz2122@columbia.edu

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

A search for track-like muon neutrino events detected by IceCube consistent with the sky
localization of the low-significance gravitational wave candidate S230628aj in a time range of 1000 seconds
centered on the alert event time (2023-06-28 16:34:04  UTC to 2023-06-28 16:50:44 UTC)
has been performed [1,2]. During this time period IceCube was collecting good quality data.
One hypothesis test was conducted for this low-significance gravitational wave event. The
search 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 S230628aj calculated from the map circulated by LVK as S230628aj-2-Preliminary. This
represents an overall pre-trial p-value of 0.0080 for the Bayesian search. The most probable
multi-messenger source direction based on the neutrinos and GW skymap is RA 147.97, Dec 8.91 degrees.

The reported p-value here does not account for any trials correction (multiple hypotheses testing).
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 event(s) are shown below.

dt(s)	RA(deg)		Dec(deg)	Angular uncertainty(deg)  p-value(generic transient) p-value(Bayesian)
-----------------------------------------------------------------------------------------------------
-301.0   147.97   	8.91    	1.509                	null (not applicable)       	0.0086
...

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