GCN Circular 28433

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

On 20/09/16 at 20:40:30.95 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 2.48 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/134498_12605830.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 20/09/16
Time:  20:40:30.95 UT
RA: 109.78 +1.08  -1.44 (deg  90% PSF containment) J2000
Dec: 14.36 +0.88  -0.85  (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 are no Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J0725.2+1425, associated with the BL Lac object 4C +14.23, at RA: 111.32 deg, Dec: 14.42 deg (1.50 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