Variability of accretion flow in the core of the Seyfert galaxy NGC 4151

This paper reports the analysis of variability data for the Seyfert 1 type active galaxy NGC 4151. It covers the optical flux history for the last 90 years and X-ray flux for last 27 years. It presents the power spectrum density and structure function, and, based on the features in these functions, discusses the properties of the accretion flow onto a supermassive black hole, presumably powering the active nucleus of the galaxy.