  Quasi-periodic fluctuations in the light curves of blazars can provide
insight into the underlying emission process. This type of flux modulation
hints at periodic physical processes that result in emission. CTA 102, a flat
spectrum radio quasar at $z=1.032$, has displayed significant activity since
2016. The multi-waveband light curve of CTA 102 shows signs of quasi-periodic
oscillations during the 2016-2017 flare. Our goal is to quantify the presence
of any periodicity in the emitted flux during the mentioned period and to
explore the causes that can give rise to it. Techniques such as the
Lomb-Scargle periodogram and weighted wavelet z-transform were employed to
observe the power emitted at different frequencies. To quantify the
significance of the dominant period, Monte-Carlo techniques were employed
considering an underlying smooth bending power-law model for the power
spectrum. In addition, the light curve was modeled using an autoregressive
process to analytically obtain the significance of the dominant period. Lastly,
the light curve was modeled using a generalized autoregressive integrated
moving average process to check whether introducing a periodic component
results in a statistically preferable model. Significant, simultaneous
quasi-periodic oscillations (QPOs) were observed in the $\gamma$-ray and
optical fluxes of blazar CTA 102 during its 2016-2017 flare. The periodic flux
modulation had a dominant period of $\sim$ 7.6 days and lasted for $\sim$ 8
cycles (MJD 57710-57770). All of the methods used point toward significant
($>4\sigma$) quasi-periodic modulation in both $\gamma$-ray and optical fluxes.
Several possible models were explored while probing the origin of the
periodicity, and by extension, the 2016--2017 optical flare. The best
explanation for the detected QPO appears to be a region of enhanced emission,
moving helically inside the jet.

High Energy Astrophysical Phenomena