Speaker
Description
Changing-Look Active Galactic Nuclei (CLAGN) undergo dramatic spectral and luminosity transitions on timescales of months to a few years— orders of magnitude shorter than the viscous timescale of a standard α-disk at the radii where the optical/UV continuum is generated, for typical supermassive black hole masses. We show that a magnetically supported disk-corona model reproduces both the observed Eddington ratio at which changing events occur and the observed transition duration. Using the diskvert code, which solves the steady vertical structure under simultaneous gas, radiation, and magnetic pressure support with a self-consistent warm corona, we (i) construct thermal-viscous S-curves, and (ii) calculate the integrated thermal timescale together with the front propagation timescale. We compute a large grid of models of different black hole masses, Eddington ratios, magnetic viscosities, and disk radii, showing that magnetised disks push the S-curve knee down to an Eddington ratio of ≈ 0.01−0.03, and introduce a new stable branch of high luminosity solutions, while the limit-cycle timescale enters the months-to-years range for BH mass $10^7−10^9 M_\odot$. Confronted with a sample of five CLAGN, the model jointly reproduces the empirical Eddington rates and the observed event durations only when the inner disk is strongly magnetised.