Kinematics of the Parsec-Scale Relativistic Jet in Quasar 3C 279: 1991 -   1997
  We present results of long-term high-frequency VLBI monitoring of the relativistic jet in 3C279, consisting of 18 epochs at 22 GHz from 1991 to 1997 and 10 epochs at 43 GHz from 1995 to 1997. Three major results of this study are: apparent speeds measured for six superluminal components range from 4.8 to 7.5 c (H_{0}=70 km s^{-1} Mpc^{-1}, q_{0}=0.1), variations in the total radio flux are due primarily to changes in the VLBI core flux, and the uniform-sphere brightness temperature of the VLBI core is about 1 x 10^{13} K at 22 GHz after 1995, one of the highest direct estimates of a brightness temperature. If the variability brightness temperature measured for 3C279 by Lahteenmaki & Valtaoja is an actual value and not a lower limit, then the rest-frame brightness temperature of 3C279 is quite high and limited by inverse Compton effects rather than equipartition. The parsec-scale morphology of 3C279 consists of a bright, compact VLBI core, a jet component (C4) that moved from about 2 mas to about 3.5 mas from the core during the course of our monitoring, and an inner jet that extends from the core to a stationary component, C5, at about 1 mas from the core. Components in the inner jet are relatively short-lived, and fade by the time they reach about 1 mas from the core. The components have different speeds and position angles from each other, but these differences do not match the differences predicted by the precession model of Abraham & Carrara. Although VLBI components were born about six months prior to each of the two observed gamma-ray high states, the sparseness of the gamma-ray data prevents a statistical analysis of possible correlations. 
A. E. Wehrle, B. G. Piner, S. C. Unwin, A. C. Zook, W. Xu, A. P.   Marscher, H. Terasranta, E. Valtaoja