Probability distribution functions of our data set in the log T_eff; log ν_max plane, in the bins M ∈ [0.9, 1.2] M_⊙ and [Fe/H] ∈ [ − 0.25, 0.0] dex. Upper left panel: 2D histogram where the AGBb is located by a blue diamond. Dark blue and light blue ellipses correspond to the 1σ and 2σ regions of the bivariate Gaussian, respectively. The red dashed line reproduces the linear term belonging to the RGB/AGB background. Upper right panel: normalised 1D histogram in log ν_max is shown in black. The ordinate axis is the same as in the upper left panel. The blue line corresponds to the probability distribution function made of the Gaussian associated to the overdensity in log ν_max, multiplied by the rising exponential in log ν_max. Lower left panel: same label as in the upper right panel but in terms of log T_eff. The abscissa axis is the same as in the upper left panel. The blue line shows the Gaussian associated to the overdensity in log T_eff. Lower right panel: difference between log ν_max and a_bglog T_eff + b_bg. The blue line illustrates the normal distribution around the linear term.