TITLE:   GCN CIRCULAR
NUMBER:  41620
SUBJECT: IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
DATE:    25/08/31 20:44:36 GMT
FROM:    Erik Blaufuss at University of Maryland, College Park <blaufuss@umd.edu>

The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2025-08-31 18:00:45.82 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 2.14 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/141300_5972385.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2025-08-31
Time: 18:00:45.82 UT  
RA: 105.64 (+0.51, -0.48 deg 90% PSF containment) J2000
Dec: 5.04 (+0.61, -0.50 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