The Compact Core-Jet Region of the Superluminal Quasar 3C 216

Space very long baseline interferometry (VLBI) observations of the quasar3C216 with the VLBI Space Observatory Programme (VSOP) reveal that the parsecscale structure of the source can be well described by compact jet modelsdeveloped for interpreting the core region of radio-loud active galactic nuclei(AGN). The measured brightness temperature of T_(b) = 7.9*10^{11} K iscomparable to the inverse Compton limit, from which we determine a lower limitof delta ~ 3.17 for the Doppler-boosting factor. The apparent transversvelocity of the superluminal component is beta_(app) = (3.0+-0.2) h^{-1}asuming a constant velocity, but deceleration of the jet material cannot beexcluded from our data. A combination of the above values indicates that theviewing angle of the core-jet to the line-of-sight is less than 18.4 degrees,and the jet Lorentz-factor exceeds 3.16. The observed small size of the sourceis probably caused by both interaction with the interstellar medium, and aprojection effect.Comment: 6 pages, 3 figures, accepted for publication by PAS