A Consolidated Framework of the Color Variability in Blazars: Long-term Optical/Near-infrared Observations of 3C 279

Abstract

Abstract We evaluate the optical/near-infrared (OIR) color variability of 3C 279 in both γ-ray flaring and non-flaring states over 7-year timescales using the Small and Medium Aperture Research Telescope System in Cerro Tololo, Chile and γ-ray fluxes obtained from the Fermi Gamma-ray Space Telescope. This observing strategy differs from previous blazar color variability studies in two key ways: (1) the reported color variability is assessed across optical through near-infrared wavelengths, and (2) the color variability is assessed over timescales significantly longer than an individual flare or ground-based observing season. We highlight 3C 279 because of its complex color variability, which is difficult to reconcile with the simple “redder-when-brighter” behavior often associated with Flat Spectrum Radio Quasar color variability. We suggest that the observed OIR color changes depend on a combination of the jet and disk emission. We parameterize this behavior in terms of a single variable, , representing a smooth transition from a disk-dominated system, to a mixed contribution, to a jet-dominated system, which provides an explanation of the long-term OIR color variability in the same blazar over time. This suggests a general scheme that could apply to OIR color variability in other blazars.