SUBJECT: Multimessenger candidate from joint gravitational-wave and high-energy neutrino search using LLAMA: low-significance LVK trigger S2468 associated with IceCube alert IceCubeCascade-230430a

The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA
Collaboration report:

A LLAMA search has been performed for LIGO/Virgo/KAGRA gravitational-wave
candidates consistent with the sky localization of IceCube alert
IceCubeCascade-230430a (** <add link to notice> **) in a time range of 1000
seconds [1] centered on the alert event time (2023-04-30 18:42:52.276 UTC to
2023-04-30 18:59:32.276 UTC).

Gravitational-wave candidate S2468 has been identified by this search. This
candidate does not meet the LIGO/Virgo/KAGRA public alert criteria based on
analysis of the gravitational-wave data alone, but it is found to be in spatial
and temporal coincidence with IceCubeCascade-230430a public alert. The
properties of the GW candidate can be found at this URL:

https://gracedb.invalid/superevents/S2468

The neutrino trigger time is xxx.xx seconds before(after) the gravitational-
wave candidate event. The p-value associated with the joint observation is
0.1228. We encourage further observation of the localization area of
IceCubeCascade-230430a and we provide a joint localization probability map at:

<gracedb link here>

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