Origin of the short-period transit-timing-variation pile-up

Determine the origin of the short-period transit-timing-variation pile-up with normalized periods P_TTV/P_orb < 10 in the Kepler data, including whether it arises from aliased high-frequency signals, stellar activity, instrumental effects, or another source.

Background

The paper finds a pronounced excess of short-period TTV signals in the Kepler observations that is absent from the ExoMOD predictions based on gravitational planet–planet interactions. The authors argue that these signals may instead result from aliasing, stellar-spot crossings, stellar activity, or observational and methodological effects.

Although several possible explanations are examined, the paper does not identify the responsible mechanism. Resolving this issue is important because short-period signals may contaminate the interpretation of the longer-period TTV population and limit the use of TTVs as constraints on planetary architectures.