Core-shift and spectral analysis of the 2006 radio flare in CTA102
  The 2006 radio flare in the blazar CTA102 is the largest ever reported for
this source. The analysis of the single--dish light curves revealed a possible
shock-shock interaction as a scenario for the 2006 outburst. In order to
confirm this hypothesis we analyzed eight multi-frequency (2 GHz - 86 GHz) VLBI
observations covering the 2006 flare. We detected a radio component ejected
around 2005.9 and a stationary feature around 0.1 mas away from the core. We
also performed a core-shift and spectral analysis on the fully calibrated VLBI
maps. The frequency dependent position of the core slightly deviates from the
typical $\nu^{-1}$-dependence during the flaring state. This behaviour may
reflect a mismatch between magnetic energy density and energy density of the
relativistic particles. From the core-shift corrected maps we obtained the
spectral parameters and computed the temporal and spatial evolution of the jet
intrinsic parameters such as the magnetic field and the particle density. The
overall picture of the source could be best interpreted as an over-pressured
jet perturbed by traveling shock waves.
