GCN Circular 41647

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-Cascade 250828A (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/141290_67759305.amon) in a time range of 1000 seconds centered on the alert event time (2025-08-28 19:22:57.520 UTC to 2025-08-28 19:39:37.520 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, one track-like event is found within the 90% containment region of IceCube-Cascade 250828A. We find that this additional event is well described by atmospheric background expectations, with a p-value of 0.28. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250828A ranges from 1.3e-01 to 6.1e+00 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 2e+02 GeV and 3e+06 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2025-08-27 19:31:17.520 UTC to 2025-08-29 19:31:17.520 UTC). In this case, we report a p-value of 0.63, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250828A ranges from 1.5e-01 to 6.2e+00 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)