TITLE:   GCN CIRCULAR
NUMBER:  30153
SUBJECT: IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
DATE:    21/06/08 07:12:18 GMT
FROM:    Cristina Lagunas Gualda at DESY  <cristina.lagunas@desy.de>

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

On 8 June 2021 at 03:41:00.98 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 3.075 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/135363_69917294.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 8 June 2021
Time:  03:41:00.98 UT
RA: 337.41 (+4.89 -11.64 deg  90% PSF containment) J2000
Dec: +18.37 (+3.75 -3.24 deg  90% PSF containment) J2000

Due to the topology of this event, with a short distance traversed through the detector, the updated angular uncertainty is significantly larger than average error contours.  

We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

There are several Fermi-LAT 4FGL sources inside the 90% localization region. The closest source is 4FGL J2235.3+1818  located at 338.84 deg and Dec 18.31 deg (J2000), at a distance of 1.35 degrees from the best-fit location.

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