Rimmed and rippled accretion disc models to explain AGN continuum lags

We propose a solution to the problem of accretion disc sizes in active galactic nuclei being larger when measured by reverberation mapping than predicted theory. Considering blackbody reprocessing on with thickness profile $H(r)$, our invokes steep rim or rippled structures irradiated central lamp-post. model continuum lags and faint bright spectral energy distribution (SED) best-studied case NGC 5548 (black hole mass $M = 7\times10^{7} M_\odot$, inclination $i=45^\circ$). With lamp-post off, observed SED requires low rate ($\dot{M} \sim 0.0014 M_\odot$/yr) high prograde black spin ($a 0.93$). Reprocessing thin gives time increasing wavelength but 3 times smaller observed. Introducing $H(r)$ rim, multiple crests, near $r 5$ light days, their centre-facing slopes increases temperatures from $\sim1500$ K $\sim6000$ this optical match lag data. Most surface maintains cooler $T\propto r^{-3/4}$ temperature that matches SED. The may be powered magnetic links tapping spin. occurs sublimation radius for dust disc, as "failed wind model" broad-line clouds. Lens-Thirring torques aligning also raise warp associated waves. In both scenarios, small density scale height implied inferred value suggests possible marginal gravitational instability disc.