TITLE: GCN CIRCULAR NUMBER: 24271 SUBJECT: ANTARES follow-up of the GW candidate S190426c DATE: 19/04/27 08:16:06 GMT FROM: Damien Dornic at CPPM,France M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite Paris Diderot), M. Colomer (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 G330687/S190426c event using the 90% contour of the probability map provided by the GW interferometers at event time. The ANTARES visibility at the time of the alert, together with the 50% and 90% contours of the probability map are shown in https://www.cppm.in2p3.fr/~dornic/events_runo3/S190426c.png . Considering the location probability provided by the LIGO/Virgo collaborations, there is a 45% chance that the GW emitter was in the ANTARES **upgoing** field of view at the time of the alert. No up-going muon neutrino candidate events were recorded in the ANTARES sky during a +/- 500s time-window centered on the time (2019-04-26 15:21:55 UT) and in the 90% contour of the G330687/S190426c event. The expected number of atmospheric background events in the region visible by ANTARES is 5.6e-4 in the +/- 500s time window. An extended search during +/- 1 hour gives no up-going muon neutrino coincidence. The expected number of atmospheric background events in the region visible by ANTARES is 4.1e-3 in this larger time window. ANTARES is the largest undersea neutrino detector, installed in the Mediterranean Sea, and it is primarily sensitive to 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.