Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert

TLDR

A high‑energy neutrino event detected by IceCube on 22 September 2017 coincided in direction and time with a gamma‑ray flare from the blazar TXS 0506+056. We investigated 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar. We examined IceCube data spanning 9.5 years, searching for excess high‑energy neutrino events from the blazar’s direction. We found a 3.5σ excess of high‑energy neutrino events from the blazar’s direction between September 2014 and March 2015, indicating blazars as the first identifiable sources of the high‑energy astrophysical neutrino flux.

Abstract

A high-energy neutrino event detected by IceCube on 22 September 2017 was coincident in direction and time with a gamma-ray flare from the blazar TXS 0506+056. Prompted by this association, we investigated 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar. We found an excess of high-energy neutrino events with respect to atmospheric backgrounds at that position between September 2014 and March 2015. Allowing for time-variable flux, this constitutes 3.5{\sigma} evidence for neutrino emission from the direction of TXS 0506+056, independent of and prior to the 2017 flaring episode. This suggests that blazars are the first identifiable sources of the high-energy astrophysical neutrino flux.