TITLE: GCN CIRCULAR NUMBER: 40128 SUBJECT: AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A DATE: 25/04/09 12:52:44 GMT FROM: Hugo Ayala at Pennsylvania State University hgayala@psu.edu

The AMON, IceCube, and HAWC collaborations report:

The AMON NuEm stream channel found a coincidence alert from the IceCube online neutrino selection + HAWC daily monitoring analysis. The analysis looks for IceCube neutrino events -mostly atmospheric in origin- around the position and transit time of a HAWC cluster of likely gamma rays, as identified in the integrated observations from a single transit, in this case having a duration of 6.06 hours.

The HAWC transit interval starts from 2025/04/09 04:21:14 UT to 2025/04/09 10:39:53 UT. A total of 6.3 hrs of integrated HAWC time.

The location of the coincidence is reported as RA (J2000): 212.8 deg Dec (J2000): 17.2 deg Location uncertainty (50% containment): 0.25 deg (statistical only). Location uncertainty (90% containment): 0.46 deg (statistical only).

The false alarm rate (FAR) of this coincidence is 1.05 per year. We encourage follow-up observations of the alert region contingent on the availability of resources and interest, given the quoted FAR.

The source 4FGL J1406.9+1643 is the closest to the best position of the coincidence, with a distance of around 1deg.

AMON seeks to perform a real-time correlation analysis of the high-energy signals across all known astronomical messengers. More information about AMON can be found in https://www.amon.psu.edu/ Information on the IceCube collaboration: http://icecube.wisc.edu/ Information on the HAWC collaboration: https://www.hawc-observatory.org

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