TITLE:   GCN CIRCULAR
NUMBER:  31931
SUBJECT: IceCube-220421A - IceCube observation of a high-energy neutrino candidate track-like event
DATE:    22/04/21 11:45:13 GMT
FROM:    Marcos Santander at U. Alabama/IceCube  <jmsantander@ua.edu>

The IceCube Collaboration (http://icecube.wisc.edu/) reports:

On 2022-04-21 at 05:20:18.26 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 2.281 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/136556_43687362.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2022-04-21
Time:  05:20:18.26 UT
RA: 113.64 (+3.17, -2.74 deg  90% PSF containment) J2000
Dec: 5.83 (+2.18, -1.69 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 listed in the 4FGL-DR3 Fermi-LAT catalog is located within the 90% containment region for the event: the source 4FGL J0733.8+0455 (RA: 113.47 deg, Dec: 4.93 deg J2000), 0.92 deg from the best-fit neutrino candidate 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 roc@icecube.wisc.edu