SMARTS optical and infrared monitoring of 12 gamma-ray bright blazars
  We present multiwavelength data for twelve blazars observed from 2008-2010 as
part of an ongoing optical-infrared photometric monitoring project. Sources
were selected to be bright, southern (dec < 20 deg) blazars observed by the
Fermi Gamma-Ray Space Telescope, with daily and weekly gamma-ray fluxes made
available from the start of the Fermi mission. Light curves are presented for
the twelve blazars in BVRJK at near-daily cadence. We find that optical and
infrared fluxes are well correlated in all sources. Gamma-ray bright flat
spectrum radio quasars (FSRQs) in our sample have optical/infrared emission
correlated with gamma-rays consistent with inverse Compton-scattering models
for GeV emission. In FSRQs, the variability amplitude decreases towards
optical/IR wavelengths, consistent with the presence of a thermal emission
component from the accretion disk varying on significantly longer timescales
than the jet synchrotron emission. In BL Lac objects, variability is mainly
constant across wavelengths, consistent with a weak or radiatively inefficient
disk. FSRQs have redder optical-infrared colors when they are brighter, while
BL Lac objects show no such trend. Several objects show complicated
color-magnitude behavior: AO 0235+164 appears in two different states depending
on whether it is gamma-ray bright or not. OJ 287 and 3C 279 show some
hysteresis tracks in their color-magnitude diagrams. Individual flares may be
achromatic or otherwise depart from the trend, suggesting different jet
components becoming important at different times. We present a time-dependent
spectral energy distribution of the bright FSRQ 3C 454.3 during its December
2009 flare, which is well fit by an external Compton model in the bright state,
although day to day changes pose challenges to a simple one-zone model. All
data from the SMARTS monitoring program are publicly available on our website.
