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TITLE:   GCN CIRCULAR
NUMBER:  30950
SUBJECT: AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211020A
DATE:    21/10/20 15:29:01 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 6.02 hours.

The HAWC transit interval starts from 10/20/2021 08:11:51 UT -
10/20/2021 14:13:37 UT
(End of the HAWC transit time)

The location of the coincidence is reported as
RA (J2000): 99.76 deg
Dec (J2000): 9.07 deg
Location uncertainty (50% containment): 0.17 deg (statistical only).
Location uncertainty (90% containment): 0.31 deg (statistical only).

The false alarm rate (FAR) of this coincidence is 0.86 per year.
We encourage follow-up observations of the alert region contingent on
the availability of resources and interest, given the quoted FAR.

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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TITLE:   GCN CIRCULAR
NUMBER:  30954
SUBJECT: AMON IC_HAWC NuEm-211020A: No neutrino counterpart detected with ANTARES
DATE:    21/10/21 14:30:28 GMT
FROM:    Antoine Kouchner at ANTARES Collaboration  <kouchner@apc.in2p3.fr>

Alexis Coleiro (APC/Universite de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration. 

Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported AMON IC-HAWC coincidence alert NuEm-211020A (https://gcn.gsfc.nasa.gov/gcn3/30950.gcn3).

No up-going muon neutrino candidate events were detected within 3 degrees from the coincidence coordinate over a time period [10h52 - 14h13 UT] corresponding to 55.8% of the HAWC transit time mentioned in the AMON notice, during which the potential source remained visible in the up-going field of view of ANTARES.

This leads to a preliminary 90% confidence level upper limit on the muon neutrino radiant fluence from a point source located at the coordinates of the coincidence as reported by AMON, of about 15 GeV.cm^-2 over the energy range 4 TeV - 4 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and about 26 GeV.cm^-2 (750 GeV - 380 TeV) for an E^-2.5 spectrum. These indicative limits have been computed for the end of the HAWC transit time.

A search over an extended time window of +/-1 day has also yielded no detection (45% visibility).

ANTARES (https://antares.in2p3.fr) is the largest undersea neutrino detector (Mediterranean Sea) and it is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky.