  Eclipsing time variations (ETVs) are observed in many close binary systems.
In particular, for several post-common-envelope binaries (PCEBs) that consist
of a white dwarf and a main sequence star, the O-C diagram suggests that real
or apparent orbital period variations are driven by Jupiter-mass planets or as
a result of magnetic activity, the so-called Applegate mechanism. The latter
explains orbital period variations as a result of changes in the stellar
quadrupole moment due to magnetic activity. We explore the feasibility of
driving ETVs via the Applegate mechanism for a sample of PCEB systems,
including a range of different rotations. Using the MESA code we evolve 12
stars with different masses and rotation rates. We apply a simple dynamo model
to their radial profiles to investigate on which scale the predicted activity
cycle matches the observed modulation period, and quantify the uncertainty, and
further calculate the required energies to drive que Applegate mechanism. We
show that the Applegate mechanism is energetically feasible in 5 PCEB systems,
and note that these are the systems with the highest rotation rate compared to
the critical rotation rate of the main-sequence star. The results suggest that
the ratio of physical to critical rotation in the main sequence star is an
important indicator for the feasibility of Applegate's mechanism, but exploring
larger samples will be necessary to probe this hypothesis.
