GCN Circular 29153
The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for additional track-like muon neutrino events arriving from the direction of IceCube-201221A (https://gcn.gsfc.nasa.gov/gcn3/29102.gcn3) in a time range of 2 days centered on the alert event time (2020-12-20 12:36:53.45 UTC to 2020-12-22 12:36:53.45 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, two additional track-like events are found in spatial coincidence with the 90% containment region of IceCube-201221A. We find that these data are consistent with atmospheric background expectations, with a p-value of 1.0. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/dE = 5.5 x 10^-5 TeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are approximately between 500 GeV and 200 TeV. A subsequent search was performed to include the month of data prior to the alert event (2020-11-21 12:36:53.45 UTC to 2020-12-22 12:36:53.45 UTC). In this case, we report a p-value of 1.0, consistent with no significant excess of track-like events, and a corresponding time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) of 6.0 x 10^-5 TeV cm^-2 at the 90% CL. 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 email@example.com<mailto:firstname.lastname@example.org>.