GCN Circular 36283

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

On 2024-04-24 at 01:49:26.0 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream.  The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.225 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/139315_50057906.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2024-04-24
Time: 01:49:26.0 UT
RA: 327.08 (+2.06, -1.70 deg  90% PSF containment) J2000
Dec: 3.06 (+1.37, -1.33 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.

Two Fermi-LAT sources (listed in the 4FGL-DR4 or 3FHL catalogs) are located in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J2149.6+0323 (J2149.8+0322 in the 3FHL catalog) at RA: 327.42 deg and DEC: 3.40 deg (0.5 deg away from the best-fit position). The second one is 4FGL J2146.8+0425 at RA: 326.71 deg and DEC: 4.43 deg, 1.4 deg away from the best-fit position. The former source is associated with a BL Lac object, while the latter is a blazar candidate of uncertain type.

Additionally, we note that a recent GRB triggered by the Swift Burst Alert Catalog (BAT) on April 19, 2024 (GRB 240419B, detection time 2024-04-19 12:22:52 UT, GCN Circular #36180), is contained within the 90% uncertainty region of the neutrino candidate event, ~1.7 deg from its best-fit 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