Multi-messenger emission from magnetic reconnection in blazar jets: the case of TXS 0506+056

TL;DR

This paper models multi-messenger emissions from blazar jets driven by magnetic reconnection, explaining the 2017 TXS 0506+056 flare with a lepto-hadronic scenario that accounts for neutrino and gamma-ray observations.

Contribution

It introduces a novel lepto-hadronic model of blazar emission driven by magnetic reconnection, explaining multi-messenger signals without external photon fields.

Findings

Reconnection accelerates particles to very high energies in blazar jets.

The model reproduces the observed sequence of neutrino and gamma-ray signals.

Predicted a time delay of about 6.4 days between neutrino and VHE gamma-ray events.

Abstract

Measurements from astroparticle experiments, such as the 2017 flare associated with the source TXS 0506+056, indicate that blazars act as multi-messenger (MM; radiation and neutrinos) factories. Theoretically, the particle acceleration mechanisms responsible for blazar emissions and the precise location within the jet where this occurs remain undetermined. This paper explores MM emission driven by magnetic reconnection in a blazar jet. Previous studies have shown that reconnection in the magnetically dominated regions of these relativistic jets can efficiently accelerate particles to very high energies (VHE). Assuming that turbulent-driven magnetic reconnection accelerates cosmic-ray protons and electrons by a Fermi process, we developed a lepto-hadronic radiation model without the influence of external soft-photons to explain the 2017 MM flare from TXS 0506+056. In the proposed scenario, the emission blob moves downstream in the jet from $\sim$2 to 4 pc from the central engine, which is a supermassive black hole (SMBH) of $3 \times 10^{8}$ M$_\odot$ launching a jet with $150L_\mathrm{Edd}$ power. As the blob moves, we observe a sequence of spectral energy distribution (SED) profiles that match the observed arrival of the high energy neutrino and electromagnetic emission from TXS 0506+056. This arrival coincides with the high state of intermediate energy $\gamma$-rays ($E \sim 1 $ GeV) detection, followed by the subsequent appearance of the VHE $\gamma$-ray signal and then no further significant neutrino detection. We obtain a time delay between the neutrino and VHE events $\simeq 6.4$ days, which is consistent with that observed in the 2017 MM flare.