  In the Sun, the frequencies of the acoustic modes are observed to vary in
phase with the magnetic activity level. These frequency variations are expected
to be common in solar-type stars and contain information about the
activity-related changes that take place in their interiors. The unprecedented
duration of Kepler photometric time-series provides a unique opportunity to
detect and characterize stellar magnetic cycles through asteroseismology. In
this work, we analyze a sample of 87 solar-type stars, measuring their temporal
frequency shifts over segments of length 90 days. For each segment, the
individual frequencies are obtained through a Bayesian peak-bagging tool. The
mean frequency shifts are then computed and compared with: 1) those obtained
from a cross-correlation method; 2) the variation in the mode heights; 3) a
photometric activity proxy; and 4) the characteristic timescale of the
granulation. For each star and 90-d sub-series, we provide mean frequency
shifts, mode heights, and characteristic timescales of the granulation.
Interestingly, more than 60% of the stars show evidence for (quasi-)periodic
variations in the frequency shifts. In the majority of the cases, these
variations are accompanied by variations in other activity proxies. About 20%
of the stars show mode frequencies and heights varying approximately in phase,
in opposition to what is observed for the Sun.
