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GCN Circular 31093

IceCube-211117A : IceCube observation of a high-energy neutrino candidate track-like event
2021-11-17T18:27:03Z (3 years ago)
Marcos Santander at U. Alabama/IceCube <>
The IceCube Collaboration ( reports:

On 2021/11/17 at 03:50:57.184 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.166 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 were attempted offline. However, the event topology of this event prevented this reconstruction from converging. Therefore, at this time we retain the online event direction as our best estimate of the event direction:

Date: 2021/11/17
Time:  03:50:57.184 UT
RA: 225.93 (+/- 0.51 deg  90% PSF containment) J2000
Dec: -0.20 (+/- 0.51 deg 90% PSF containment) J2000

We note that the online error estimates are unchanged from the initial online alert estimates, and are potentially underestimated compared to those from the offline reconstructions. We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

There are no Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J1512.2+0202 at RA: 228.07 deg, Dec: 2.04 deg (3.10 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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