TITLE: GCN CIRCULAR NUMBER: 24378 SUBJECT: IceCube-190503A - IceCube observation of a high-energy neutrino candidate event DATE: 19/05/03 20:51:47 GMT FROM: Erik Blaufuss at U. Maryland/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 19/05/03 at 17:23:08 UT IceCube detected a track-like, very-high-energy event with a high probability of being of astrophysical origin. The  event was identified by the Extremely High Energy (EHE) track event selection.  The IceCube detector was in a normal operating state.  EHE events typically have a neutrino interaction vertex that is outside the detector, produce a muon that traverses the detector volume, and have a high light level (a proxy for energy). After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon/42419327_132508.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 19/05/03 Time: 17:23:08.72 UT RA: 120.28 (+0.57 -0.77 deg  90% PSF containment) J2000 Dec: 6.35 (+0.76 -0.70 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% region. The nearest known gamma-ray source is 4FGL J0800.9+0733 at RA: 120.2262 deg, Dec: 7.5509 deg (1.2 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