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GCN Circular 27612

IceCube-200421A - IceCube observation of a high-energy neutrino candidate event
2020-04-21T03:10:12Z (4 years ago)
Erik Blaufuss at U. Maryland/IceCube <>
The IceCube Collaboration ( reports:

On 21 April, 2020 at 00:35:24.24 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 threshold astrophysical neutrino purity for  Bronze alerts is 30% . This alert has an estimated false alarm rate of  2.8 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 (, more  sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 21 April 2020
Time:  00:35:24.24 UT
RA: 87.93 (+3.44/- 2.83 (+1.88/-1.64) deg  90% (50%) PSF containment) J2000
Dec: 8.23 (+2.09/-1.84 (+1.25/-1.19) deg 90% (50%) 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 are no Fermi 4FGL or 3FHL catalog sources in the 50% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J0545.0+0613 at RA: 86.27 deg, Dec: 6.23 deg (2.59 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
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