TITLE: GCN CIRCULAR NUMBER: 36918 SUBJECT: IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 24/07/21 20:11:48 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli@icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2024-07-21 at 16:17:25.8 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 1.376 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/139674_30853199.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2024-07-21 Time: 16:17:25.8 UT RA: 354.99 (+1.08, -1.14 deg 90% PSF containment) J2000 Dec: 22.67 (+1.38, -1.14 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-DR4 or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J2338.9+2124 at RA: 354.74 deg, Dec: 21.40 deg J2000 (1.29 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/36918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...