Neutrinos from blazars

TL;DR

This paper discusses the significance of neutrino detections from blazars, especially TXS 0506+056, as evidence for relativistic protons in jets and their role as cosmic-ray accelerators, using multi-messenger modeling.

Contribution

It presents the first constraints on blazar hadronic models derived from neutrino observations, linking neutrino data to jet physics in active galactic nuclei.

Findings

Neutrino detections support the presence of relativistic protons in blazar jets.

Multi-messenger modeling constrains hadronic models of blazars.

Implications for understanding jet physics from super-massive black holes.

Abstract

The evidence for joint gamma and neutrino emission from the blazar TXS 0506+056 has renewed interest in blazars as neutrino sources. The detection of neutrinos from blazars can be seen as the smoking gun for the presence of relativistic protons in blazar's jets, and can thus help identify blazars, and active galactic nuclei in general, as cosmic-ray accelerators. In this contribution I first introduce blazars and blazar hadronic models, and then present the results of the multi-messenger modeling of both the 2017 gamma-neutrino flare, and the 2014-2015 neutrino-only flare of TXS 0506+056. For the first time it is possible to constrain blazar hadronic models using the information from neutrino detectors, and I discuss the implications of these neutrino observations on our understanding of the physics of relativistic jets from super-massive black-holes.