Rotation and spot activity of young solar-type stars from long-term photometric monitoring

We present results from a recent multidecade study of the spot activity of young solar-like stars, based on photometry gathered at the Fairborn observatory since 1987. Results from the time series analysis of this photometry reveal systematic tendencies in the stellar rotation and activity behaviour: 1) Fast rotating stars show weaker relative surface differential rotation but the absolute equator to pole differential rotation has a flat rotation dependence. 2) The lengths of activity cycles follow a set of tightly defined parallel branches when compared to the Rossby number and chromospheric activity levels. A number of stars show superimposed cycles from two different branches. 3) Active longitudes are commonly seen on the highly active stars, but on weakly active stars the long-term distribution of spot activity is axisymmetric. There appears to be a sharp boundary between the axisymmetric and non-axisymmetric regimes, suggesting a shift in the dominant dynamo modes. 4) The active longitudes have commonly significantly shorter rotation periods than the stellar surfaces, as measured directly from the shorter lived spot modulation. This may be a signature of radial differential rotation or that the active longitudes follow an azimuthal dynamo wave.