TITLE: GCN CIRCULAR NUMBER: 42352 SUBJECT: IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/18 11:11:12 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli@icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-18 at 05:05:42.97 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 0.2566 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/141495_22018019.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-18 Time: 05:05:42.97 UT RA: 321.11 (+3.09/-2.94 deg 90% PSF containment) J2000 Dec: 41.31 (+2.46/-3.51 deg 90% PSF containment) J2000 Two gamma-ray sources listed in the Fermi 4FGL-DR4 catalog are located within the 90% uncertainty region of the event, both with no clear multi-wavelength counterpart and classification: 4FGL J2118.3+4055 and 4FGL J2120.5+433, situated 1.3 deg and 2.3 deg away from the best-fit direction of our alert, respectively. We encourage follow-up observations by both ground- and space-based instruments to help identify a possible astrophysical counterpart to the candidate neutrino. 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/42352. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...