Abstract
Context. Until a few years ago, the amplitude variation in the
photometric data had been explored to a limited extent mainly because of
time resolution and photometric sensitivity limitations. This
investigation is now possible thanks to the Kepler and CoRoT databases
which provide a unique set of data for studying the nature of stellar
variability cycles.
Aims. The present study characterizes the amplitude variation in a
sample of main-sequence stars with light curves collected using CoRoT
exofield CCDs.
Methods. We analyze potential stellar activity cycles by studying the
variability amplitude over small boxes. The cycle periods and amplitudes
were computed based on the Lomb-Scargle periodogram, harmonic fits, and
visual inspection. As a first application of our approach, we considered
the photometric data for 16 CoRoT FGK main sequence stars, revisited
during the IRa01. LRa01 and LRa06 CoRoT runs.
Results. The 16 CoRoT stars appear to follow the empirical relations
between activity cycle periods (P-cyc) and the rotation period (P-rot)
found by previous works. In addition to the so-called A (active) and I
(inactive) sequences previously identified, there is a possible third
sequence, here named S (short-cycles) sequence. However, recovery
fractions estimated from simulations suggest that only a half of our
sample has confident cycle measurements. Therefore, more study is needed
to verify our results, and Kepler data will clearly be useful for such a
study. Overall, our procedure provides a key tool for exploring the
CoRoT and Kepler databases to identify and characterize stellar cycle
variability.
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