The Long-Lasting Activity in the Flat Spectrum Radio Quasar (FSRQ)
  CTA~102
  The flat spectrum radio quasar CTA 102 ($z = 1.032$) went through a
tremendous phase of variability. Since early 2016 the gamma-ray flux level has
been significantly higher than in previous years. It was topped by a four month
long giant outburst, where peak fluxes were more than 100 times higher than the
quiescence level. Similar trends are observable in optical and X-ray energies.
We have explained the giant outburst as the ablation of a gas cloud by the
relativistic jet that injects additional matter into the jet and can
self-consistently explain the long-term light curve. Here, we argue that the
cloud responsible for the giant outburst is part of a larger system that
collides with the jet and is responsible for the years-long activity in CTA
102.
