TITLE:   GCN CIRCULAR
NUMBER:  35905
SUBJECT: IceCube-240307A: Upper limits from a search for additional neutrino events in IceCube
DATE:    24/03/08 17:18:14 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-240307A (https://gcn.nasa.gov/circulars/35898) in a time range of 1000 seconds centered on the alert event time (2024-03-07 07:36:37.380 UTC to 2024-03-07 07:53:17.380 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-240307A. We find that this additional event is well described by atmospheric background expectations, with a p-value of 0.07. 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-240307A ranges from 1.4e-01 to 1.7e-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 (2024-03-06 07:44:57.380 UTC to 2024-03-08 07:44:57.380 UTC). In this case, we report a p-value of 0.75, 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-240307A ranges from 1.6e-01 to 2.0e-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)