TITLE:   GCN CIRCULAR
NUMBER:  20926
SUBJECT: Search for counterpart to IceCube-170321A with ANTARES 
DATE:    17/03/21 17:30:43 GMT
FROM:    Damien Dornic at CPPM,France  <dornic@cppm.in2p3.fr>

D. Dornic (CPPM/CNRS), A. Coleiro (APC/Universite Paris Diderot) on behalf of the ANTARES Collaboration:

Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported single high-energy (HESE) neutrino IceCube-170321A (AMON IceCube EHE 80305071 129307). The reconstructed origin was 57 degrees below the horizon for ANTARES, with this position remaining below the horizon from -9h, +5h around the time of the alert. Thus ANTARES had a high sensitivity to any neutrinos from the same region.

No up-going muon neutrino candidate events were recorded within three degrees of the IceCube event coordinates during a +/- 1h time-window centered on the IceCube event time. A search on an extended time window of +/- 1 day has also yielded no detection (58% visibility probability).

This yields a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 16 GeV.cm^-2 over the energy range 2.5 TeV-2.5 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 26 GeV.cm^-2 (510 GeV-220 TeV) for an E^-2.5 spectrum.

ANTARES is the largest neutrino detector installed in the Mediterranean Sea, and is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range.  At 10 TeV, the median angular resolution for muon neutrinos is below 0.5 degrees. In the range 1-100 TeV, ANTARES has the best sensitivity to this position in the sky.