GCN Circular 25091

M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite de Paris), M. Colomer 
(APC/Universite de Paris), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite de Paris), 
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 S190718y event using the 90% contour of the bayestar probability
map provided by the GW interferometers (GCN#25087). The ANTARES visibility at the time of the
alert, together with the 50% and 90% contours of the probability map are shown at 
http://antares.in2p3.fr/GW/S190718y.png <http://antares.in2p3.fr/GW/S190718y.png>. Considering the location probability provided by the 
LIGO/Virgo collaborations, there is a 77.5% 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 2019-07-18 14:35:12 and in the 90% contour of the S190718y
event. The expected number of atmospheric background events in the region visible by ANTARES is
1.88e-03 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 1.36e-02 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.