Characterizing the Long-Term Optical and Infrared Color Variability of a Sample of Southern Hemisphere Blazars

We undertook a 6-year, multiwavelength program to observe a sample of blazars in various Fermi gamma-ray states, using the Small and Medium Aperture Research Telescope System (SMARTS) 1.3m + ANDICAM instrument in Cerro Tololo, Chile. We present near-daily optical and infrared (OIR) color variability diagrams for a sample of 12 blazars. We then compare the OIR flux and color to the Fermi gamma-ray flux on similar cadence. We show that on long timescales (of order years), patterns emerge in the OIR color variability that are not seen on shorter timescales due to selection effects introduced by observing blazars in gamma-ray bright, jet-flaring states. By observing both active and quiescent jet flaring states, we show that previous short-term color variability behavior, e.g. 'redder when brighter' in FSRQs and 'bluer when brighter' in BL Lacs, represent ‘snapshots’ in a given blazars' color variability behavior over time. We present a schematic representation of the long-term OIR color variability in blazars, and propose that changes in the relative contribution of the disk and jet emission, migration of the gamma-emitting region to outside the broad line region, and injections of higher energy electrons in the jet itself contribute to the long-term OIR color variability that we observe.