TITLE:   GCN CIRCULAR
NUMBER:  40195
SUBJECT: IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
DATE:    25/04/21 21:07:00 GMT
FROM:    Giacomo Sommani at Ruhr-Universität Bochum <gsommani@icecube.wisc.edu>

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

On 25-04-21 at 17:06:08.07 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 1.0254 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 (http://gcn.gsfc.nasa.gov/notices_amon_g_b/140824_2517159.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 25-04-21
Time: 17:06:08.07 UT
RA: 240.91 (+2.62/-4.44 deg 90% PSF containment) J2000
Dec: 28.67 (+1.70/-1.70 deg 90% PSF containment) J2000

This neutrino candidate event traversed through the corner of the instrumented IceCube volume, yielding an event direction reconstruction with larger than average uncertainties.   We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

There are four Fermi 4FGL-DR4 or 3FHL catalog sources in the 90% uncertainty region: 4FGL J1606.5+2717 at RA: 241.64 deg, Dec: 27.30 deg J2000 (1.51 deg away from the best-fit event position); 4FGL J1556.1+2812 at RA: 239.05 deg, Dec: 28.21 deg J2000 (1.70 deg away from the best-fit event position); and 4FGL J1555.3+2903 at RA: 238.83 deg, Dec: 29.06 deg J2000 (1.86 deg away from the best-fit event position); and 4FGL J1612.2+2828 at RA: 243.06 deg, Dec: 28.47 deg J2000 (1.90 deg away from the best-fit event 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