Optical and GeV flux variations in Fermi blazars

Abstract

A large fraction of γ-ray emitting blazars show correlated flux variations in the optical and γ-ray bands with little or no time lag. However, in a minority of them, uncorrelated optical and γ-ray flux variations are seen. From an analysis of the optical R-band light curves from the Small and Moderate Aperture Research Telescope System (SMARTS) and γ-ray light curves from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, we find three sources that show correlated optical and γ-ray flux variations at some epochs and uncorrelated variations at other epochs. These findings pose serious challenges to our current understanding of the various emission processes in the jets of blazars.