A characteristic optical variability time scale in astrophysical accretion disks

Accretion disks around supermassive black holes in active galactic nuclei produce continuum radiation at ultraviolet and optical wavelengths. Physical processes the accretion flow lead to stochastic variability of this emission on a wide range timescales. We measure observed 67 characteristic timescale which power spectrum flattens. find correlation between hole mass, extending over entire mass holes. This is consistent with expected thermal ultraviolet-emitting radius standard disk theory. Accreting white dwarfs lie close correlation, suggesting common process for all disks.