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3C 66A is an intermediate-frequency-peaked BL Lac object detected by theLarge Area Telescope onboard the Fermi Gamma-ray Space Telescope.  We present a study of the long-term variations of this blazar seen over 2years at GeV energies with Fermi and in the optical (flux and polarization) andnear infrared with the Kanata telescope.  In 2008, the first year of the study, we find a correlation between thegamma-ray flux and the measurements taken with the Kanata telescope.  This is in contrast to the later measurements performed during 2009--2010which show only a weak correlation along with a gradual increase of the opticalflux. We calculate an external seed photon energy density assuming that thegamma-ray emission is due to external Compton scattering. The energy density ofthe external photons is found to be higher by a factor of two in 2008 comparedto 2009--2010. We conclude that the different behaviors observed between thefirst year and the later years might be explained by postulating two differentemission components.

A Study of the Long-term Spectral Variations of 3C 66A Observed with the Fermi and Kanata Telescopes