GCN Circular 20370
M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite Paris Diderot), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite Paris Diderot), T. Pradier (IPHC/Universite de Strasbourg) report on behalf of the ANTARES Collaboration: Using on-line data from the ANTARES detector, we have performed a follow-up analysis of the recently reported LIGO/Virgo G268556 event using the initial LIGO BAYESTAR probability map at event time. The ANTARES visibility at the time of the alert together with the 90% contour of the probability map are shown in: https://www.cppm.in2p3.fr/~dornic/events/G268556.png (gwantares/ANT@GW). Considering the location probability provided by the LIGO collaboration, there is a 50.6% chance that the GW emitter was in the ANTARES field of view. ANTARES, being installed in the Mediterranean Deep Sea, is the largest neutrino detector in the Northern Hemisphere. It 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 a large fraction of the Southern sky. No up-going muon neutrino candidate events were recorded within the 90% contour during a +/- 500s time-window centered on the G268556 event time. An estimate of the upper limit on the associated neutrino fluence will be sent in a subsequent circular.