TITLE: GCN CIRCULAR NUMBER: 38349 SUBJECT: IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event DATE: 24/11/27 16:03:36 GMT FROM: A. Zegarelli at Ruhr University Bochum azegarelli@icecube.wisc.edu

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

On 2024-11-27 at 14:11:14.42 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.28 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/140125_41215060.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2024-11-27 Time: 14:11:14.42 UT RA: 164.09 (+0.46, -0.52 deg 90% PSF containment) J2000 Dec: 5.38 (+0.58, -0.55 deg 90% PSF containment) J2000

No Fermi 4FGL or 3FHL catalog sources are in the 90% uncertainty region. However, given the promising characteristics of the candidate neutrino event, we encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source associated with it.

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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