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GCN Circular 31110

IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
2021-11-24T03:30:28Z (3 years ago)
Marcos Santander at U. Alabama/IceCube <>
The IceCube Collaboration ( reports:

On 2021-11-23 at 14:25:22.6 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream.  The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.567 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.

After the initial automated alert (, more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2021-11-23 
Time: 14:25:22.6 UT
RA: 265.52 (+3.14 -2.84 deg  90% PSF containment) J2000
Dec: 7.33 (+2.38 -2.48 deg 90% PSF containment) J2000

Both the initial alert and subsequent offline reconstructions were delayed as computing resources were undergoing maintenance. We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

Two gamma-ray sources listed in the 4FGL Fermi-LAT catalog, 4FGL J1736.6+0628 and 4FGL J1734.0+0805, are located within the 90% error region for the event, located 1.6 and 2.1 deg away from the best-fit position, respectively. 

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
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