Electron-positron pair plasma in TXS 0506+056 and the 'neutrino flare' in 2014-2015

The detection of a prolonged flaring activity from blazar TXS 0506+056 in temporal and spatial coincidence with the energetic neutrino IceCube-170922A provided evidence about the photohadronic interactions in this source. However, analysis of the archival neutrino and multiwavelength data from the direction of this blazar between 2014 September and 2015 March revealed a 'neutrino flare' without observing quasi-simultaneous activity in the gamma-ray bands, posing challenges to established models. Electron-positron (e(+/-)) pairs generated from the accretion discs have been amply proposed as a mechanism of bulk acceleration of sub-relativistic and relativistic jets. These pairs annihilate inside the source producing a line around the electron mass, which is blueshifted in the observed frame (on Earth) and redshifted in the frame of the dissipation region of the jet. The redshifted photons in the dissipation region interact with accelerated protons, producing high-energy neutrinos that contribute significantly to the diffuse neutrino flux in the similar to 10-20 TeV energy range in connection with gamma-rays from the photopion process, which can be detected by future MeV orbiting satellites. Based on this phenomenological model, we can explain the 'neutrino flare' reported in 2014-1015.