Speaker
Description
Accreting supermassive black holes that undergo Changing-look events on timescales of months to a few years cannot be explained by standard accretion-disk theory; the radiation-pressure instability sets on at Eddington ratios well above the observed transition band and the viscous timescales are much longer than the observed duration.
We show that a magnetically supported disk-corona model satisfies both constraints simultaneously. By constructing thermal-viscous stability maps and computing transition timescales directly from the converged vertical structure, we find that strongly magnetised configurations (i) bring the stability threshold to the empirical band at which transitions are observed to occur, and (ii) place the transition timescale in the months-to-years range, matching the observed durations. Both diagnostics independently localise the instability in the inner accretion flow. We compare the model predictions with a sample of five well-characterised Changing-Look AGN and find consistent constraints on the disk magnetisation across the sample, indicating a unified magnetised-disk origin for the Changing-Look phenomenon.