[vsnet-grb-info 23021] LIGO/Virgo S190720a : no neutrino counterpart candidate in ANTARES search

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25120
SUBJECT: LIGO/Virgo S190720a : no neutrino counterpart candidate in ANTARES search
DATE:    19/07/20 10:12:24 GMT
FROM:    Antoine Kouchner at ANTARES Collaboration  <kouchner at apc.in2p3.fr>

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 S190720a event using the 90% contour of the bayestar probability
map provided by the GW interferometers (GCN#25115 <https://gcn.gsfc.nasa.gov/gcn3/25115.gcn3>). 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/S190720a.png <http://antares.in2p3.fr/GW/S190720a.png>.
Considering the location probability provided by the LIGO/Virgo collaborations, there is a
41.6% 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 2019-07-20 00:08:36 and in the 90% contour of the S190720a event. 
The expected number of atmospheric background events in the region visible by ANTARES is 3.50e-04 in the +/- 500s time window. 
An extended search during +/- 1 hour gives no upgoing muon neutrino candidate in coincidence with the 90% contour. 
In this extended time window, an event (Time = 01:06:24, RA=200.3deg, Dec=7.6 deg) is seen outside the 99% contour, close to the ANTARES horizon.
Considering the expected number of atmospheric background events in the ANTARES upgoing field of view, this had a ~10% chance to occur.

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.