TITLE:   GCN CIRCULAR
NUMBER:  20517
SUBJECT: LIGO/Virgo G268556: ANTARES upper limits
DATE:    17/01/24 18:01:13 GMT
FROM:    Damien Dornic at CPPM/CNRS  <dornic@cppm.in2p3.fr>

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:

The ANTARES Collaboration has reported in GCN 20370, no up-going muon neutrino candidate event within the 90% contour during a +/- 500s time-window centered on the G268556 event time.

We use this non-detection to derive a neutrino (nu_mu+antinu_mu) spectral fluence instantaneous upper limit at 90% C.L. (phi_0 in GeV/cm^2), defined as dN/dE = phi_0* E^{-2} assuming a E^{-2} neutrino spectrum. The result is reported in https://www.cppm.in2p3.fr/~dornic/events/G268556_fluenceE2.png <https://www.cppm.in2p3.fr/~dornic/events/G268556_fluenceE2.png> (gwantares/ANT@GW) as a function of the source direction. These neutrino fluence limits range between 1 and 3 GeV/cm^{2} depending on the source direction. For a E^{-2} neutrino spectrum, 90% of ANTARES signal neutrinos are in the energy range from 2.8 TeV to 3.2 PeV (mean value over the sky).

From the 3D GW localization and the neutrino spectral fluence upper-limits, the preliminary upper limits on the total energy radiated in high-energy neutrinos over the GW skymap are computed for the progenitor of G268556 as a function of the source direction assuming a a E^{-2} neutrino spectrum integrating in the range [100 GeV-100 PeV]: https://www.cppm.in2p3.fr/~dornic/events/G268556_energyE2.png <https://www.cppm.in2p3.fr/~dornic/events/G268556_energyE2.png> (gwantares/ANT@GW). The total neutrino emission limits range between 10^{54} and 10^{55} ergs.

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.