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GCN Circular 31241

IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
2021-12-16T10:16:16Z (2 years ago)
Dr. Massimiliano Lincetto at Ruhr-Universitaet Bochum <>
The IceCube Collaboration ( reports:

On 2021-12-16 at 07:07:38.13 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 2.37 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: 2021-12-16
Time: 07:07:38.13

RA: 316.05 (+2.58/-1.95 deg 90% PSF containment) J2000
Dec: 15.79 (+1.29/-1.63 deg 90% PSF containment) J2000

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 are located in the 90% containment region. The sources are 4FGL J2100.0+1445 at RA: 315.02 deg, Dec: 14.76 deg (1.43 deg away from the best-fit event position) and 4FGL J2108.5+1434 at RA: 317.15, Dec: 14.58 (1.61 deg away from the best-fit event position).

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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