Presentation #129.01 in the session AGN and Quasars II.
AGNs in the UV/optical exhibit aperiodic and stochastic variability on timescales ranging from days to years. Although this phenomenon has been known for decades, the exact physical mechanisms driving it are still poorly understood. In recent years, a damped random walk (DRW) model has been widely utilized to describe AGN variability in the UV/optical statistically. However, higher quality light curves from the Kepler Mission have revealed steeper slopes in their power spectrum density (PSD) than that specified by the DRW model at high frequencies. In this talk, we will introduce the damped harmonic oscillator (DHO) model — a second-order stochastic diffusion process that permits more flexible shapes in its PSD, and present the result of applying this model to a large sample of AGNs/quasars observed in the SDSS Stripe 82 area. We will re-examine AGN variability using the information extracted from the light curves by the DHO model in addition to the variability amplitude and the decay timescale characterized by the DRW model, and explore potential correlations between DHO parameters and physical properties of AGN.