AGN Flickering and Chaotic Accretion
  Observational arguments suggest that the growth phases of the supermassive
black holes in active galactic nuclei have a characteristic timescale $\sim
10^5$ yr. We show that this is the timescale expected in the chaotic accretion
picture of black hole feeding, because of the effect of self-gravity in
limiting the mass of any accretion disc feeding event.
