Variable Accretion Disks
We present a study of 9258 quasars observed with multi-epoch ugriz photometry with spectroscopic redshifts as part of the SDSS Southern Survey. Using a linear model to fit the spectral variations, we isolate separate spectra for the variable (disc) non-variable(disc + galaxy) components of each quasar. We find evidence for bluer spectral slopes than predicted by cannonical accretion disc theory and excellent agreement with SMC-like dust extinction. This work provides the first direct evidence to support recent groundbreaking theoretical efforts to analytically describe accretion discs in the context of General Relativity and magnetic stress.