TITLE: GCN CIRCULAR NUMBER: 26258 SUBJECT: IceCube-191119A - IceCube observation of a high-energy neutrino candidate event DATE: 19/11/19 02:49:07 GMT FROM: Erik Blaufuss at U. Maryland/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: On Nov 19, 2019 at 01:01:29.38 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 threshold astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.54 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/133331_47828126.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 19/11/19 (yy/mm/dd) Time: 01:01:29.38 UT RA: 230.10 (+4.76/-6.48 deg 90% PSF containment) J2000 Dec: 3.17 (+3.36/-2.09 deg 90% PSF containment) J2000 The geometry of this event was near the edge of the instrumented volume of IceCube and yielded a somewhat larger 90% uncertainty region when compared to typical realtime alert events. We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. Several gamma-ray sources listed in the 4FGL Fermi-LAT catalog are located within 90% containment region about the best-fit candidate neutrino position. The closest source is 4FGL J1518.8+0203, located 1.2 deg away from the best-fit position. A total of 11 sources listed in the 4FGL catalog are contained in a 5 deg radius from the best-fit position, which approximately corresponds to the 90% containment radius of the event. 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