Variability study and searching for quasiperiodic oscillations with day-like periods in the blazar S5 0716+714 with TESS

Abstract

Using an unprecedented cadence of 30 minutes provided by the Transiting Exoplanet Survey Satellite, we have examined the optical light curves (LCs) of the blazar S5 0716+714 obtained from its Sectors 40, 47, and 53 over a period of about 75 days. This source exhibited flux variability in each of those sectors, reaching a maximum variability amplitude of 5.6%. The power spectral density shapes were tested with a simple power law and two distinct bending power laws and were found to be better fit by bending power laws than simple power laws for all but one of the segments. To look for any periodicities in these LCs, we used weighted wavelet Z transform analysis and generalized Lomb–Scargle periodograms. We identified one possible quasiperiodic oscillation signature in a portion of sector 40 (period of ∼6.5 hr), having ∼95% global significance. A statistical approach to assess the LCs involving continuous autoregressive moving average was implemented, and the LCs were found to follow more complex processes than the simplest and typical damped random walk process. We briefly discuss the statistical properties of the LCs along with the general variability features and physical processes that could cause these types of fluctuations.