Three-year VLBI monitoring of PKS 0420–014

We present nine 3.6-cm VLBI observations of the optically violent variable (OVV) flat-spectrum radio quasar PKS 0420–014 taken over a period of three years (1989.32– 1992.48); we also show a VLBI map from observations at 43 GHz in 1992.4. We trace jet evolution and variability with individual components. We find superluminal motion with βapp ∼ 2–14c for five jet components. Components ejected more recently seem to separate faster from the core. All jet components follow one common curved path within the jet. In addition to presenting the results of the VLBI monitoring, we discuss a possible correlation between component ejection and outbursts seen in the radio/optical/gamma-ray regimes. The ejection of several jet components can be linked to flares in the cm-light curves; the most recently ejected component appeared shortly before a simultaneous radio/optical/gamma-ray flaring. Our results are in agreement with the predictions of the lighthouse model of Camenzind & Krockenberger (1992), which explains the observed optical flaring. We introduce an alternative model involving a precessing binary black hole.