Lepto-hadronic γ-Ray and Neutrino Emission from the Jet of TXS 0506+056

Abstract

The observation of the IceCube-170922A event from the direction of TXS 0506+056 when it was in its enhanced γ -ray emission state offers a unique opportunity to investigate the lepto-hadronic processes in blazar jets. Here, the observed broadband emission of TXS 0506+056 is explained by boosted synchrotron/synchrotron self Compton emission from the jet, whereas the γ -ray data observed during the neutrino emission by inelastic interactions of the jet-accelerated protons in a dense gaseous target. The proton energy distribution is , calculated straightforwardly from the data obtained by the Fermi Large Area Telescope ( Fermi -LAT) and the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC); if such a distribution continues up to E c , p  = 10 PeV, the expected neutrino rate is as high as ∼0.46 events during the long active phase of the source or ∼0.15 if the activity lasts 60 days. In this interpretation, the energy content of the protons above >GeV in blazar jets can be estimated as well: the required proton injection luminosity is ≃2.0 × 10 48 erg s −1 exceeding 10 3 times that of electrons ≃10 45 erg s −1 , which are in equipartition with the magnetic field. As the required parameters are physically realistic, this can be an acceptable model for an explanation of the neutrino and γ -ray emission from TXS 0506+056.