Reduced phase shift and central small frequency separation for RGB (circles) and core He-burning stars (triangles) with the symbol colours coded according to stellar mass. Inserts show the mass dependency of the various parameters along with a linear fit (red lines). In the insert of the top panel, RGB and RC stars are indicated by grey circles and black triangles, respectively. Note that stars with Δν_c below 1.5 μHz are excluded here because their uncertainties are too large. Colours are given only in the online version.