TITLE: GCN CIRCULAR NUMBER: 21769 SUBJECT: LIGO/Virgo G299232 ANTARES search (2) DATE: 17/08/30 16:09:41 GMT FROM: Damien Dornic at CPPM/CNRS M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (IFIC & APC), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite Paris Diderot), T. Pradier (IPHC/Universite de Strasbourg) report on behalf of the ANTARES Collaboration: GCN #21696 reported the ANTARES search for upward going High Energy Neutrinos from LIGO/Virgo G299232 event, for which only 42% of the initial 90% C.L contour map was visible (with upward going events). We report here on a dedicated analysis looking for down-going neutrino candidates in the on-line ANTARES data stream. Cuts on the quality of the track reconstruction and an energy proxy have been used to reduce the false alarm rate in such a way that one event matching in time (+/- 500 s) and direction (90% C.L contour) with G299232 would result in a 3-sigma excess. The ANTARES visibility, for down-going events, 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/G299232/250817_down.png (gwantares/GW@ANT51) No down-going muon neutrino candidate events were recorded by ANTARES within the 90% C.L. contour and during a ± 500 s time-window centered on the G299232 event time. An extended search during ± 1 hour yields no coincidence. 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.