Parsec-Scale Jet Behavior of the Quasar 3C 454.3 during the High   Gamma-Ray States in 2009 and 2010
  We analyze total and polarized intensity images of the quasar 3C 454.3 obtained monthly with the VLBA at 43 GHz within the ongoing Boston U. monitoring program of gamma-ray blazars started in June 2007. The data are supplemented by VLBA observations performed during intense campaigns of 2 week duration when the quasar was observed 3 times per campaign. We find a strong increase of activity in the parsec-scale jet of the quasar during high gamma-ray states in December 2009, April 2010, and November 2010. We detect new superluminal knots, K09 and K10, associated with the autumn 2009 and 2010 outbursts, respectively, and compare their kinematic parameters. We analyze optical polarimetric behavior along with polarization parameters of the parsec-scale jet and outline similarities and differences in polarization properties across wavelengths. The results of the analysis support the conclusions that the optical polarized emission is produced in a region located in the vicinity of the mm-wave core of the jet of the quasar, and that the gamma-ray outbursts occur when a superluminal disturbance passes through the core. 
S. G. Jorstad, A. P. Marscher, M. Joshi, N. R. MacDonald, T. L. Scott,   K. E. Williamson, P. S. Smith, V. M. Larionov, I. A...
astro-ph.HE