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

TL;DR

This paper reports evidence of neutrino emission from the blazar TXS 0506+056 prior to the 2017 IceCube alert, indicating blazars as potential sources of high-energy astrophysical neutrinos based on 9.5 years of data.

Contribution

It presents the first evidence of neutrino emission from TXS 0506+056 before the 2017 flare, highlighting blazars as sources of high-energy neutrinos.

Findings

3.5σ evidence for neutrino emission from TXS 0506+056 between 2014-2015

Neutrino excess independent of the 2017 gamma-ray flare

Blazars as potential sources of high-energy astrophysical neutrinos

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.