Results from a decade-long VLBI astrometric monitoring of the pair of quasars 1038+528 A and B

We present results from three epochs, spanning nearly a decade, of VLBI monitoring of the angular separation between the quasars 1038+528 A and B. Our observations, made simultaneously at λ 3.6 cm and λ 13 cm, achieve submilliarcsecond (submas) precision in the measurement of the∼33” separation between the two quasars.We detected changes in this angular separation of nearly 0.2 mas. These changes can be explainedwholly, or mostly, by themotion of the reference feature used in quasar B which appears to be a component in the jet, separating from the core at a speed near c. We also conclude that any proper motion of quasar A is less than 10 μas yr−1. There is an intriguing hint of a “jitter” in the position of the peak brightness of this quasar, but the signal-to-noise ratio is too low for us to draw a firm conclusion.