TITLE:   GCN CIRCULAR
NUMBER:  30627
SUBJECT: IceCube-210811A - IceCube observation of a high-energy neutrino candidate track-like event
DATE:    21/08/11 03:53:19 GMT
FROM:    Marcos Santander at U. Alabama/IceCube  <jmsantander@ua.edu>

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

On 21/08/11 at 02:02:44.04 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 0.694 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/135591_36044887.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 21/08/11 UT
Time:  02:02:44.04 
RA: 270.79 (+1.07, -1.08 deg  90% PSF containment) J2000
Dec: 25.28 (+0.79, -0.84 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.

There is one Fermi-LAT 4FGL gamma-ray source located within the 90% error region, 4FGL J1803.3+2425 (RA = 270.84 deg, Dec = 24.43 deg J2000) at a distance of 0.85 deg from the best-fit neutrino 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