One of the known observables related to the Horizontal Branch (HB) and Asymptotic Giant Branch (AGB) evolution is the AGB bump. Its luminosity depends on the position in mass of the helium-burning shell at its first ignition, that is affected by the extension of the central mixed region.

In this poster we present evidence for the AGB bump in Kepler's giants, and how its use as an estimator of the overall size of the mixed core in He-burning stars. In our preliminary work we use the MESA code (Modules for Experiments in Stellar Astrophysics, Paxton et al. 2013) to study the treatment of central mixing, by considering the effects of different amounts of overshooting. We show how various assumptions on mixing and thermal stratification in the overshooting region affect the seismic observables, in particular the period spacing. We also investigate the effects of glitches in the structure (e.g due to of partial mixing in the “semiconvective” region) on the detailed properties of the period spacing.