TITLE:   GCN CIRCULAR
NUMBER:  31110
SUBJECT: IceCube-211123A - IceCube observation of a high-energy neutrino candidate track-like event
DATE:    21/11/24 03:30:28 GMT
FROM:    Marcos Santander at U. Alabama/IceCube  <jmsantander@ua.edu>

The IceCube Collaboration (http://icecube.wisc.edu/) 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 (https://gcn.gsfc.nasa.gov/notices_amon_g_b/135930_15193553.amon, 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 roc@icecube.wisc.edu