Catching the radio flare in CTA 102

In this paper we study the kinematics of CTA 102 at several frequencies using VLBI observations. From the modeled jet features we derived estimates for the evolution of the physical parameters, such as the particle density and the magnetic field. Furthermore ,we combined our observations during the 2006 flare with long-term VLBA monitoring of the source at 15 GHz and 43 GHz We cross-identified seven features throughout our entire multifrequency observations and find evidence of two possible recollimation shocks around 0.1mas (deprojected 18pc at a viewing angle of 2.6{deg} and 6.0mas (deprojected 1kpc) from the core.

The 43GHz observations reveal a feature ejected at epoch t_ej_=2005.9+/-0.2, which could be connected to the 2006 April radio flare. Furthermore, this feature might be associated with the traveling component involved in the possible shock-shock interaction, which gives rise to the observed double peak structure in the single-dish light curves reported in Paper I, 2011A&A...531A..95F.