GCN Circular 27242

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

 Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported HAWC-200216A alert (Notice https://gcn.gsfc.nasa.gov/notices_amon_hawc/19170_50.amon). <br><br>

No up-going muon neutrino candidate events were detected within 3 degrees from the event coordinates over a time window of [T0-3.4h, T0+8.6h]where T0 is the time of the HAWC alert, and during which the potential source remained visible in the up-going field of view of ANTARES. At T0, the elevation of the alert is 36 degrees below the horizon for ANTARES. A search over an extended time window of +/-1 day has also yielded no detection (50% visibility). <br><br>

 This leads to a preliminary 90% confidence level upper limit on the muon-neutrino radiant fluence from a point source of about 16 GeV.cm^-2 over the energy range 3.2 TeV ��� 3.4 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and about 27 GeV.cm^-2 (615 GeV - 315 TeV) for an E^-2.5 spectrum, computed for the time of the Swift Busrt Alert. <br><br>

ANTARES 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.