Optical Variability as a Probe of Accretion and Jet Dominance in Active Galactic Nuclei

Optical variability probes the innermost regions of active galactic nuclei (AGN), where accretion discs and relativistic jets remain spatially unresolved. Disc variability reflects stochastic fluctuations in the accretion flow, whereas relativistically beamed jet emission can produce stronger, more rapid, and less damped variations. Distinguishing these components is essential for understanding AGN physics and interpreting variability timescales from large photometric surveys. I will present results from Zwicky Transient Facility (ZTF) light curves and dedicated photometric monitoring, combining continuum reverberation mapping, damped random walk (DRW) modelling, and structure function (SF) analysis across intra-night to multi-year timescales. ZTF reverberation mapping of 19 AGN reveals accretion-disc sizes three to four times larger than predicted by the standard Shakura–Sunyaev model. In radio-loud narrow-line Seyfert 1 galaxies, rapid optical variability occurs almost exclusively in γ-ray-detected jetted sources, while non-jetted sources remain comparatively quiescent. On multi-year baselines, SFs exhibit a systematic progression with jet dominance: highly polarised quasars show the highest and steepest SFs, followed by γ-ray-detected jetted AGN, whereas non-jetted sources approach a plateau consistent with disc-driven variability. Together, these results suggest that relativistic beaming plays a key role in shaping optical variability, beyond the mere presence of a radio jet. Long-term SFs offer a complementary diagnostic of jet contributions, particularly when short baselines compromise DRW parameter recovery. This distinction is crucial for the Rubin Observatory Legacy Survey of Space and Time (LSST), where unrecognised jet variability could bias inferred characteristic timescales and black hole mass estimates. I will conclude by discussing how these diagnostics could be developed to quantify disc and jet contributions to optical variability in the Rubin era.