Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 30957

IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
2021-10-23T09:47:02Z (3 years ago)
Dr. Massimiliano Lincetto at Ruhr-Universitaet Bochum <>
The IceCube Collaboration ( reports:

On 2021/10/23 at 08:31:18.31 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 3.2 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: 2021/10/23
Time:  08:31:18.31 UT
RA: +253.30 (+1.05 / -1.08 deg  90% PSF containment) J2000
Dec: -1.72 (+1.16 / -1.11 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.

One gamma-ray source, 4FGL J1653.6-0158, is located within the 90% of the error region, 0.27 deg away from the best-fit position. The source is associated with the pulsar PSR J1653-0158.

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
Looking for U.S. government information and services? Visit