Correlated radio and optical variability in the BL Lacertae object 0716 + 714

Abstract

We present results from simultaneous optical and radio observations of the BL Lacertae object 0716+714. During a 4 week period of continuous monitoring the source displayed in both wavelength regimes a transition between states of fast and slow variability with a change of the typical variability time scale from 1 day to 7 days. We interpret the simultaneous transition as evidence for intrinsic source variability, and we discuss some consequences for the optical and radio emission regions.