TITLE: GCN CIRCULAR NUMBER: 40247 SUBJECT: IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/04/25 14:18:59 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison thwaites@wisc.edu
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-250421A (https://gcn.nasa.gov/circulars/40195) in a time range of 1000 seconds centered on the alert event time (2025-04-21 16:57:48.070 UTC to 2025-04-21 17:14:28.070 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-250421A. 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-250421A is 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 2e+02 GeV and 7e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2025-04-20 17:06:08.070 UTC to 2025-04-22 17:06:08.070 UTC). In this case, we report a p-value of 0.26, 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-250421A ranges from 1.6e-01 to 1.7e-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)
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