# The Long-Lasting Activity in the Flat Spectrum Radio Quasar (FSRQ) CTA~102

## TL;DR

This paper analyzes the prolonged activity and giant outburst of the FSRQ CTA 102, attributing it to interactions between a gas cloud and the jet, explaining multi-wavelength variability over several years.

## Contribution

It introduces a model linking long-term activity and giant outbursts in CTA 102 to cloud-jet interactions, providing a self-consistent explanation for observed variability.

## Key findings

- Giant outburst caused by gas cloud ablation by jet
- Long-term activity linked to larger cloud system interactions
- Multi-wavelength variability explained by cloud-jet dynamics

## Abstract

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.