Superimposed on this feature is a secondary modulation with a full amplitude of 0.06 days and a recurrent time scale of about 30 years.
Irregular recurrence rules out attempts to explain these period modulations as being due to apsidal precession or the presence of distant, unseen companions.
[3] The time scale and recurrence patterns of these orbital period modulations suggested to Matese and Whitmire (1983) a mechanism invoking changes in the quadrupole moment of one star with subsequent spin-orbit coupling.
[4] Taking the Matese and Whitmire mechanism as a basis, Applegate argued that changes in the radius of gyration of one star could be related to magnetic activity cycles.
[6][7] The Applegate effect provides a unified explanation for many (but not all) ephemeris curves for a wide class of binaries, and it may aid in the understanding of the dynamo activity seen in rapidly rotating stars.
[8] The Applegate mechanism has also been invoked to explain variations in the observed transit times of extrasolar planets, in addition to other possible effects such as tidal dissipation and the presence of other planetary bodies.