GCN Circular 25402

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

On 2019-08-19 at 17:34:24.24 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 3.9 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/132974_67924813.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2019-08-19
Time:  17:34:24.24 UT
RA: 148.80 (+2.07 -3.24 deg  90% PSF containment) J2000
Dec: 1.38 (+1.00 -0.75 deg 90% PSF containment) J2000

The Fermi-LAT catalogue source 4FGL J0946.2+0104, associated with a BL Lac object at a redshift of z = 0.58, is located within the 90% uncertainty region of the event with an offset of 1.1 degrees from the best-fit neutrino location. This source is also listed as 3FHL J0946.2+0104 in the 3FHL catalog of hard Fermi-LAT gamma-ray sources.

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

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<mailto:roc@icecube.wisc.edu>