TITLE: GCN CIRCULAR NUMBER: 28210 SUBJECT: IceCube-200806A: IceCube observation of a high-energy neutrino candidate event DATE: 20/08/06 15:46:44 GMT FROM: Robert Stein at DESY The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 20/08/06 at 13:50:56.43 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 0.792 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/134354_59221243.amon ), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 20/08/06 Time: 13:50:56.43 UT RA: 157.25 (+1.21 -0.89 deg 90% PSF containment) J2000 Dec: 47.75 (+0.65 -0.64 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 sources located within the 90% localization region. The nearest gamma-ray source is 4FGL J1015.0+4926, located at RA: 153.77 deg, Dec: 49.43 deg (2.85 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