Big Signals, Small Signals, Systematics

We examine the role of instrumental systematics in the search for small amplitude signal components in the presence of large amplitude signals. Current analyses of variable stars dealing with the above situation seem to ignore the effects of systematics, albeit the consideration of systematics is quite routine in the field of extrasolar planets. We show that simultaneous filtering of the large amplitude component and the systematics leads to residuals with much better potentials to detect any hidden small amplitude components. The method is illustrated by selected examples from the Kepler database.