Optical/{gamma}-ray flares for Fermi-LAT blazars

We explore correlated optical/{gamma}-ray flux variations for 178 Fermi-LAT blazars regularly monitored by the Katzman Automatic Imaging Telescope, the Small and Moderate Aperture Research Telescope System, and the Steward Observatory. Out of the 178 sources, 121 show a measurable (>1{sigma}) discrete correlation function peak.

Using the derived time lags and Bayesian block light-curve decompositions, we measure the fraction of common and orphan flares between the two bands. After accounting for sampling and sensitivity limitations we quantify for the first time the true orphan flare rates of optical and {gamma}-ray flares: 54.5% of optical and 20% of {gamma}-ray flares are orphan events. Both the intraband temporal relation and the small orphan {gamma}-ray flare fraction point toward leptonic processes as the likely mechanisms for the high-energy emission.