0446+11 15GHz VLBA images in Stokes I, Q, U

This is consistent with an extremely small jet viewing angle below 1 deg, inferred from the parsec-scale polarization structure. The flare can be reproduced by the injection of a proton population and an increase in the Doppler factor from 18 to 24. We also detected an approximately 90 deg rotation of the EVPA in the parsec-scale core during the initial phase of the flare, indicating the emergence of a shock formed by the change in the bulk plasma speed.

Our comprehensive multimessenger analysis demonstrates that the extreme beaming and subdegree viewing angle of this distant blazar can account for the observed neutrino and electromagnetic activity. These findings strengthen the case for blazars as efficient accelerators of hadrons and significant contributors to the observed high-energy neutrino flux.