Multi-messenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A

TL;DR

This paper reports the first multi-messenger observation linking a high-energy neutrino to a flaring gamma-ray blazar, supporting the hypothesis that blazars are sources of cosmic neutrinos.

Contribution

It provides the first direct association between a high-energy neutrino and a specific astrophysical source, a flaring blazar, through multi-wavelength observations.

Findings

Neutrino IceCube-170922A was detected at 290 TeV.

The neutrino's arrival was spatially coincident with blazar TXS 0506+056.

TXS 0506+056 was observed in a flaring state across multiple wavelengths.

Abstract

Individual astrophysical sources previously detected in neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017 we detected a high-energy neutrino, IceCube-170922A, with an energy of approximately 290 TeV. Its arrival direction was consistent with the location of a known gamma-ray blazar TXS 0506+056, observed to be in a flaring state. An extensive multi-wavelength campaign followed, ranging from radio frequencies to gamma-rays. These observations characterize the variability and energetics of the blazar and include the first detection of TXS 0506+056 in very-high-energy gamma-rays. This observation of a neutrino in spatial coincidence with a gamma-ray emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.