TITLE: GCN CIRCULAR NUMBER: 31122 SUBJECT: IceCube-211123A: Upper limits from a search for additional neutrino events in IceCube DATE: 21/11/24 22:29:54 GMT FROM: Alex Pizzuto at ICECUBE/U of Wisconsin The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-211123A (https://gcn.gsfc.nasa.gov/gcn3/31110.gcn3) in a time range of 1000 seconds centered on the alert event time (2021-11-23 14:17:02.600 UTC to 2021-11-23 14:33:42.600 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-211123A. The IceCube sensitivity assuming an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) to neutrino point sources within the locations spanned by the 90% spatial containment region of IceCube-211123A ranges from 1.3e-01 to 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2021-11-22 14:25:22.600 UTC to 2021-11-24 14:25:22.600 UTC). In this case, we report a p-value of 0.10, consistent with no significant excess of track events. The IceCube sensitivity assuming an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) to neutrino point sources within the locations spanned by the 90% spatial containment region of IceCube-211123A ranges from 1.5e-01 to 1.6e-01 GeV cm^-2 in a 2 day time window. 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] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)