TITLE: GCN CIRCULAR NUMBER: 41235 SUBJECT: IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/08/05 07:56:02 GMT FROM: A. Zegarelli at Ruhr University Bochum azegarelli@icecube.wisc.edu

The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-08-04 20:16:26.65 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 2.2075 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/141198_19914656.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2025-08-04 Time: 20:16:26.65 UT RA: 79.50 (+0.51, -0.52 deg 90% PSF containment) J2000 Dec: 16.65 (+0.49, -0.45 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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