TITLE: GCN CIRCULAR NUMBER: 33403 SUBJECT: IceCube-230306A - IceCube observation of a high-energy neutrino candidate DATE: 23/03/06 13:31:19 GMT FROM: Dr. Massimiliano Lincetto at Ruhr-Universitaet Bochum The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2023-03-06 at 10:59:30.41 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 0.71 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/137711_79205800.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2023-03-06 Time: 10:59:30.41 UT RA: 72.86 (+0.87/-0.89 deg 90% PSF containment) J2000 Dec: +34.23 (+0.87/-0.86 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. There are no Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J0444.6+3425 at RA: 71.16 deg, Dec: 34.42 deg (1.42 deg away from the best-fit event position). 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