The source of variable optical emission is localized in the jet of the   radio galaxy 3C 390.3
  We present observational evidence for the link between variability of the radio emission of the relativistic jet and optical continuum emission in the radio galaxy 3C 390.3 which indicates that the source of variable non-thermal continuum radiation is located in the innermost part of the relativistic jet. We suggest that the continuum emission from the jet ionizes material in a subrelativistic outflow surrounding the jet, which results in a formation of a conical region with broad emission lines at a distance of about 0.4 parsecs from the central nucleus. 
Tigran G. Arshakian, Andrei P. Lobanov, Vahram H. Chavushyan, Alla I.   Shapovalova and J.Anton Zensus