TITLE: GCN CIRCULAR NUMBER: 20857 SUBJECT: IceCube-170312A - IceCube update on a high-energy neutrino candidate event DATE: 17/03/13 02:29:21 GMT FROM: Erik Blaufuss at U. Maryland/IceCube Erik Blaufuss (U. of Maryland) reports on behalf of the IceCube Collaboration (http://icecube.wisc.edu/). On 03 March, 2017 IceCube detected a track-like, very-high-energy event with a possibility of being of astrophysical origin. The event was identified by the High Energy Starting Event (HESE) selection. The IceCube detector was in a normal operating state. HESE events have a neutrino vertex inside of the detector (to reduce background) and have a high light level (a proxy for energy). After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon/65274589_129281.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2017-03-12 Time: 13:49:39.83 UT RA: 305.15 deg (<+/- 0.5 ra uncertainty> deg 90% PSF containment) J2000 Dec: -26.61 deg (<+/- 0.5 dec uncertainty> deg 90% PSF containment) J2000 Additionally, after closer inspection of the event details, it shows signs of being consistent with rare atmospheric muon background events that are expected from the realtime event selection. 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