Abstract
Active Galactic Nuclei (AGNs) are the most luminous objects in the universe and are thought to be powered by the accretion of matter onto a million to a billions solar mass black hole. AGNs emit immense amount of luminosity in almost all part of the electromagnetic spectrum and therefore it is assumed that a range of physical processes are going on in the AGN. However, the optical emission that we are primarily concerned with comes from the thermal black body emission.
Soon after its discovery, it was realised that AGNs varies a lot. However, the fundamental cause of such variability is largely unknown. In this project we have explored the AGNs optical variability as a consequence of fluctuations in accretion rates. Since AGNs light curves are stochastic and aperiodic in nature, we applied a coherent first order auto regressive perturbation to the thermal black body emission. We also calculated the ratio of amplitude of variability in two optical bands of SDSS stripe 82 data and showed that a coherent radius dependent ampltude of fluctuations which might arise out of inward moving perturbations can not only explain the simultaneous variability across all AGN bands, but can also explain the observed higher ratio of amplitude of variability in two optical bands.