Description
Standard accretion disc theory predicts that AGN accretion disc cannot vary on observable time-scales, instead attributing the observed optical/UV variations to the re-processing of X-rays originating from a low-density corona. In recent years the intensive black hole monitoring campaigns (IBRM) have challenged this picture, often showing poor correlations between the optical/UV and X-ray as well as optical/UV variability amplitudes inconsistent with that expected from disc reprocessing. Fairall 9, a local bare Seyfert 1 AGN, was recently subject to a ~1000 day IBRM campaign, providing one of the richest current IBRM datasets and a unique window into its accretion structure. These data show a sharp rise after ~300 days in the optical/UV, with a corresponding evolution in the spectral energy distribution (SED) suggesting a global change to the system driven by an increase in the mass-accretion rate. Here I will show results indicating a significant departure from standard accretion disc theory, and suggest that even non-changing-look AGN are possibly non-stationary on observable time-scales, impacting how we interpret future monitoring campaigns.
