Magnetic activity cycles in the open cluster NGC 6811?

The sun shows a magnetic activity cycle related to the occurrence of spots on its surface with a strong periodicity of 11 years. With the advent of space missions like CoRoT and Kepler, astronomers began to try and find ways to associate the photometric variability of the star with its intrinsic magnetic activity. Photometric proxies for activity appear to be correlated with the chromospheric $\mathcal{S}$ index and p-modes from asteroseismology. In order to investigate the existence and properties of magnetic cycles in a narrow range of fundamental parameters, we studied solar-type stars in the intermediate-age open cluster NGC 6811. We searched our sample for cycle-like periodicities and in each case classified the variability as either cyclic, multicyclic, flat or acyclic. We checked the usual correlations between $P_{\rm cyc}$, $P_{\rm rot}$ and Rossby number and we find a high degree of dispersion among them, which casts doubt on the existence of the Active branch. We introduce theoretical questions about what determines the activity cycle period and whether there is some sort of fundamental difference between cyclic and acyclic stars. The comparison between stars with the same mass, age and chemistry suggests that neither of these properties is truly decisive.