Abstract:
We investigate the possible presence of quasi-periodic oscillation (QPO) signals in 2103 blazars from the Zwicky Transient
Facility (ZTF) time-domain survey. We detect a low-frequency QPO signal in five blazars observed over these 3.8-yr-long optical
r-band ZTF light curves. These periods range from 144 to 196 d detected at 4σ significance levels in both the Lomb–Scargle
periodogram and weighted wavelet Z-transform analyses. We find consistent results using the phase dispersion minimization
technique. A similar peak is detected in the g-band light curves at a slightly lower significance of 3σ. Such nearly periodic
signals on these time-scales in optical wavebands most likely originate from a precessing jet with high Lorentz factor, closely
aligned to the observer’s line of sight or the movement of plasma blobs along a helical structure in the jet.
