TITLE: GCN CIRCULAR NUMBER: 33094 SUBJECT: IceCube-221223A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 22/12/23 15:59:58 GMT FROM: Marcos Santander at U. Alabama/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2022-12-23 at 07:43:00.52 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 average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.246 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. The automated offline reconstruction pipeline that is used to generate refined directions encountered technical issues that require additional investigations to resolve. The event itself was examined using a graphical event display and is considered of good quality. At this time, the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/137467_64735045.amon) is the best information available: Date: 2022-12-23 Time: 07:43:00.52 UT RA: 350.54 +/- 0.67 deg (90% PSF containment) J2000 Dec: +34.71 +/- 0.67 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. We note that the error estimates from the initial automated alerts can underestimate the angular uncertainty after considering systematic errors and an additional update is planned once the more sophisticated algorithms in our standard pipeline are successfully applied. One gamma-ray source listed in the 4FGL Fermi-LAT catalog is located within the preliminary 90% uncertainty radius of the event. The source is 4FGL J2322.7+3436 / TXS 2320+343 (RA: 350.68 deg, Dec: 34.61 deg J2000, 0.15 deg away from the best-fit position) and is associated to a BL Lac object. 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