SIMBAD references

Parametric resonance between the perturbation of a stellar convective zone affected by a companion of a close binary system and non-axisymmetric dynamo modes can play an important role in close binary systems. This process in combination with the previously suggested α² -mechanism is probably responsible for strongly non-axisymmetric magnetic activity observed in several close binaries. The conditions required for swing excitation to occur in such systems are directly related to the status of rotational synchronization between the orbital motion and rotation of the star, which can be used as a tool to discover such objects. One potential candidate - an active RS CVn-type star ER Vulpeculae - shows indications of the swing excitation.