Multiperiodicity, modulations and flip-flops in variable star light curves: II. Analysis of II Pegasus photometry during 1979–2010

According to previously published Doppler images of the magnetically active primary want component of the RS CVn binary II Peg, the surface of the star was dominated by one single active longitude that was clearly drifting in the rotational frame of the binary system during 1994-2002; later imaging for 2004-2010, however, showed decreased and chaotic spot activity, with no signs of the drift pattern. Here we set out to investigate from a more extensive photometric dataset whether this drift is a persistent phenomenon, in which case it could be caused either by an azimuthal dynamo wave or be an indication that the binary system's orbital synchronization is still incomplete. There is some evidence that the regular drift without phase jumps is related to the high, state, while the complex phase behavior and disrupted drift pattern are related to the low state of magnetic activity. The most natural explanation of the drift is weak anti-solar differential rotation with a coefficient k [approximate]0002 combined with the preferred latitude of the spot structure.