The Connection between the Radio Jet and the γ-Ray Emission in 3C120 and CTA102

We present multi-wavelength studies of the blazar CTA102 and the radio galaxy 3C120 during bright gamma-ray flares for both sources. The Fermi Large Area Telescope registered in September-October 2012 an extraordinary bright gamma-ray outburst in the quasar CTA102, and between December 2012 and October 2014 a prolonged gamma-ray activity in the radio galaxy 3C120. In both studies the analysis of Fermi data has been compared with a series of 43 GHz VLBA images from the VLBA-BU-BLAZAR program, providing the necessary spatial resolution to probe the parsec scale jet evolution during the high energy events. In the case of 3C120, in order to extend the observing period covered by radio data, we also used 15 GHz VLBA data from the MOJAVE sample. Although these two objects represent very different classes of AGN, we found they have similar properties during the gamma-ray events. The gamma-ray flares are associated with the passage of a new superluminal knot through the mm VLBI core, but not all ejections of new components lead to gamma-ray events and components responsible for the gamma-ray emission are not necessary bright components. Both in CTA102 and in 3C120, gamma-ray events occurred only when the new components are moving in a direction closer to our line of sight. We locate the gamma- ray dissipation zone a short distance downstream of the radio core but outside of the broad line region, suggesting synchrotron self-Compton scattering as the probable mechanism for the gamma-ray production