The Rapid Optical Variability of the Nearby Radio-Loud AGN Pictor A: Introducing the Quaver Pipeline for AGN Science with TESS

Abstract

The sampling strategy of the Transiting Exoplanet Survey Satellite (TESS) make TESS light curves extremely valuable to investigate high cadence optical variability of AGN. However, because the TESS instrument was primarily designed for exoplanet science, the use of the satellite for other applications requires careful treatment of the data. In this paper we introduce Quaver, a new software tool designed specifically to extract TESS light curves of extended and faint sources presenting stochastic variability. We then use this new tool to extract light curves of the nearby radio-loud AGN Pictor A, and perform a temporal and power spectral analysis of its high cadence optical variability. The obtained light curves are well fit with a damped random walk (DRW) model, exhibiting both stochastic AGN variations and flaring behavior. The DRW characteristic timescales $\tau_{\rm DRW} \sim 3-6$ days during more quiet periods, and $\tau_{\rm DRW} \sim 0.8$ days for periods with strong flares, even when the flares themselves are masked from the DRW fit. The observed timescales are consistent with the dynamical, orbital and thermal timescales expected for the low black hole mass of Pictor A.