Multi-epoch VSOP observations of 1928+738

Abstract

We have undertaken a series of eight VSOP observations of the relatively low-redshift ( z=0.3) core-dominated quasar 1928+738 in order to test the claims by Roos et al. [AJ 409 (1993) 130] that on the pc-scale this source shows evidence of a super-massive binary black hole system in the form of a precessing ballistic relativistic jet. We have detected a wide range of proper motions from nearly stationary (0.02 mas/yr or 0.5 c) to relatively fast (0.82 mas/yr or 19 c). We also find that the observed kinematics are more consistent with a ballistic precessing relativistic jet model than a relativistic helical jet model.