GCN Circular 26832

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

On 20/01/17 at 18:48:18.56 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 0.36 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/133644_43767651.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 20/01/17 
Time: 18:48:18.56 UT
RA:  67.46 (+0.36 -0.43  deg 90% PSF containment) J2000
Dec: -14.63  (+0.32 -0.25  deg 90% PSF containment) J2000

This event had a down-going topology with an extremely large deposited charge in the detector, and was consequently reconstructed with a likely neutrino energy in excess of 6 PeV. We caution that, despite this high energy, there is a known atmospheric muon-bundle background that can produce similar events. The astrophysical signalness of this event is thus 33%, as reported in the initial notice. 

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

There are no 4FGL sources inside the 90% localization region. The closest source is 4FGL J0438.4-1254 located at RA 69.61 deg and dec -12.91 deg (at a distance of 2.71 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