TITLE: GCN CIRCULAR NUMBER: 26655 SUBJECT: IceCube-200107A: IceCube observation of a high-energy neutrino candidate event DATE: 20/01/07 17:36:04 GMT FROM: Robert Stein at DESY The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 20/01/07 at 09:42:18.36 UT IceCube detected a high-energy starting event [1]. Though it did not pass the Gold or Bronze starting track classification, a new neural network classifier identified the event as a starting track. Visual inspection is consistent with this classification. High-energy starting events have a rate of ~12 per year, out of which ~2 per year are starting tracks. Because the event was not identified as either Gold or Bronze, we do not currently report a false alert rate or signalness. However, given the topology and light deposition of this event, we identify it as a potential astrophysical neutrino of interest to the community. The IceCube detector was in a normal operating state at the time of detection. Sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 20/01/07 Time: 09:42:18.36 UT RA: 148.18 (+ 2.20 - 1.83 deg 90% PSF containment) J2000 Dec: 35.46 (+ 1.10 - 1.22 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 two Fermi 4FGL sources located within the 90% localization region. The nearest gamma-ray source is 4FGL J0955.1+3551 at RA: 148.78 deg, Dec: 35.86 deg (0.63 deg away from the best-fit event position). Another source, 4FGL J0957.8+3423, is located at RA: 149.47 deg, Dec: 34.40 (1.50 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 [1] The IceCube Collaboration, Phys. Rev. Lett. 113, 101101 (2014)