Catching the radio flare in CTA 102: II. VLBI kinematic analysis
  We performed multifrequency multiepoch Very Long Baseline Array (VLBA)
observations of the blazar CTA 102 during its 2006 radio flare, the strongest
ever reported for this source. These observations provide an excellent
opportunity to investigate the evolution of the physical properties of blazars,
especially during these flaring events. We want to study the kinematic changes
in the source during the strong radio outburst in April 2006 and test the
assumption of a shock-shock interaction. This assumption is based on the
analysis and modeling of the single-dish observations of CTA\,102 (Paper I). 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 0.1
mas (deprojected 18 pc at a viewing angle of 2.6 degrees) and 6.0 mas
(deprojected 1 kpc) from the core. The 43 GHz observations reveal a feature
ejected at epoch $t_\mathrm{ej}=2005.9\pm0.2$, 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.
