Probing the Drivers of Optical Variability in Active Galactic Nuclei

Optical variability is a defining characteristic of Active Galactic Nuclei (AGN) and serves as a critical tool for understanding the dynamics of supermassive black holes (SMBHs), the structure and behaviour of accretion discs, and the interplay of multi-wavelength emission processes. Despite its ubiquity, the underlying physical mechanisms responsible for long-term optical variability remain poorly understood, necessitating detailed studies across diverse AGN populations. In this talk, I will present the results of our comprehensive investigation into the optical variability characteristics of AGN, utilising approximately five years of high-cadence light curve data from the Zwicky Transient Facility (ZTF) in conjunction with the 105-month Swift Burst Alert Telescope (BAT) AGN catalogue. We examine correlations between optical variability amplitudes and timescales with fundamental AGN parameters such as SMBH mass, bolometric luminosity, and Eddington ratio, providing insights into the influence of accretion disc physics and thermal emission processes. In addition, we explore the potential impact of X-ray spectral properties, including photon indices and fluxes, which trace high-energy radiative mechanisms, and investigate the role of radio characteristics, such as flux densities and radio loudness, as proxies for jet activity. Our findings reveal a robust positive correlation between variability timescales and both SMBH mass and luminosity, indicating the significant role of these parameters in shaping long-term optical variability. Conversely, X-ray and radio properties exhibit weak or no significant relationships, suggesting that high-energy processes and jet activity exert minimal influence on optical variability. These results reinforce the dominance of thermal processes in the accretion disc as the primary drivers of long-term variability. I will also discuss the potential for future studies to extend this work by incorporating larger, more diverse samples and leveraging multi-wavelength data to develop unified models of AGN variability across the electromagnetic spectrum.