Variability Study and Searching for QPOs with day-like periods in the blazar S5 0716+714 with TESS

TL;DR

This study analyzes TESS optical light curves of blazar S5 0716+714 over 75 days, identifying potential quasi-periodic oscillations and characterizing variability using advanced spectral and statistical methods.

Contribution

It introduces a detailed variability analysis of S5 0716+714 with TESS data, detecting a possible QPO and applying novel statistical approaches to understand its complex light curve behavior.

Findings

Detected a ~6.5 hour QPO candidate with 95% significance.

Light curves follow complex processes beyond simple damped random walk.

Power spectral density better fit by bending power laws.

Abstract

Using an unprecedented cadence of 30 minutes provided by the Transiting Exoplanet Survey Satellite (TESS), 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 (PSD) 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 (WWZ) transform analysis and generalized Lomb-Scargle periodograms (LSPs). We identified one possible quasi-periodic oscillation (QPO) signature in a portion of sector 40 (period of ~6.5 h), having ~95% global significance. A statistical approach to assess the light curves involving continuous autoregressive moving average (CARMA) was implemented, and the light curves were found to follow more complex processes than the simplest and typical damped random walk process. We briefly discuss the statistical properties of the light curves along with the general variability features and physical processes that could cause these types of fluctuations.