Search for Neutrinos in Super-Kamiokande associated with the GW170817 neutron-star merger

TL;DR

This study searched for neutrinos coincident with the neutron-star merger GW170817 using Super-Kamiokande but found no signals, setting upper limits on neutrino fluence across a wide energy range.

Contribution

First to perform a comprehensive neutrino search associated with GW170817, establishing upper limits on neutrino emission from neutron-star mergers.

Findings

No significant neutrino signals detected.

Set upper limits on neutrino fluence for energies above 1.6 GeV.

Set fluence limits for neutrinos below 100 MeV.

Abstract

We report the results of a neutrino search in Super-Kamiokande for coincident signals with the first detected gravitational wave produced by a binary neutron star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to $\sim$100 PeV, in a time window $\pm$500 seconds around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is $16.0^{+0.7}_{-0.6}$ ($21.3^{+1.1}_{-0.8}$) cm$^{-2}$ for muon neutrinos (muon antineutrinos), with an error range of $\pm5^{\circ}$ around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of $-2$. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is $6.6 \times 10^7$ cm$^{-2}$ for anti-electron neutrinos under the assumption of a Fermi-Dirac spectrum with average energy of 20 MeV.