TITLE:   GCN CIRCULAR
NUMBER:  31128
SUBJECT: IceCube-211125A: No neutrino counterpart detected with ANTARES
DATE:    21/11/26 09:55:17 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 bronze track event IceCube-211125A (GCN #31126 <https://gcn.gsfc.nasa.gov/gcn3/31126.gcn3>). The reconstructed origin was 6 degrees below the horizon for ANTARES at the time of the alert.

No muon neutrino candidate events were recorded within 90% error box of the IceCube event during a +/- 1h time-window centered on the IceCube event time, and over which the potential source remained visible 82.5% of the time window. This leads to a preliminary 90% confidence level upper limit on the muon-neutrino radiant fluence from a point source of about 12 GeV.cm^-2 over the energy range 5 TeV – 5 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 35 GeV.cm^-2 (1 - 500 TeV) for an E^-2.5 spectrum. 

A search over an extended time window of +/- 1 day has also yielded no detection (37% visibility). 

ANTARES <http://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.