SUBJECT: Neutrino candidates from joint gravitational-wave and high-energy neutrino search using LLAMA: low-significance LVK trigger S2468

The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA
Collaboration along with the IceCube Collaboration (http://icecube.wisc.edu/)
report:

Searches have been performed for track-like muon neutrino events  detected by
IceCube consistent with the the time and sky localization of the gravitational-
wave (GW) candidate S2468. The GW candidate's properties can be found at this
URL:

https://gracedb.invalid/superevents/S2468

Based on the analysis of gravitational-wave data alone, this candidate does not
meet LIGO/Virgo/KAGRA criteria for a public alert.

IceCube data was searched in a time range of 1000 seconds [1] centered on the
GW event time (2023-04-30 18:42:52.276 UTC to 2023-04-30 18:59:32.276 UTC).
During this time period IceCube was collecting good quality data. The
hypothesis test employed by LLAMA uses a Bayesian approach to quantify the
joint GW + neutrino event significance. [2] From this analysis, 5 track-like
events were found in spatial and temporal coincidence with the gravitational-
wave candidate S2468.

Properties of the coincident neutrinos together with the p-values associated
with the joint observation are shown below.

dt         ra        dec      Angular Uncertainty(deg)     p-value
------------------------------------------------------------------
332.85     44.53     22.87              2.97               0.1228
217.96     59.56     -35.77             0.20               0.1228
186.93     117.77    -14.39             0.20               0.1228
0.00       43.11     -0.58              0.73               0.1228
-161.59    277.09    41.44              2.09               0.1228

where:
dt = Time offset (sec) of track event with respect to GW trigger.
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

Further information about analysis methodology can be found at
https://multimessenger.science/.
For further information about analysis methodology and the contents of this
alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide
https://emfollow.docs.ligo.org/.

 [1] Baret et al., Astroparticle Physics 35, 1 (2011)
doi:10.1016/j.astropartphys.2011.04.001
 [2] Bartos et al. PRD 100, 083017 (2019) doi:10.1103/PhysRevD.100.083017 and
Countryman et al. (2019) arXiv:1901.05486