TITLE: GCN CIRCULAR NUMBER: 40254 SUBJECT: IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/04/26 19:17:00 GMT FROM: A. Zegarelli at Ruhr University Bochum azegarelli@icecube.wisc.edu

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

On 25-04-26 at 17:44:58.16 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.2610 events per year due to atmospheric Backgrounds. The IceCube detector was in a normal operating state at the time of detection.

After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140843_52432631.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 25-04-26 Time: 17:44:58.16 UT RA: 296.37 (+0.53/-0.50 deg 90% PSF containment) J2000 Dec: 20.7 (+0.52/-0.52 deg 90% PSF containment) J2000

We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event.

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

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