Morphology of the age posterior probability distribution function (PDF) for different positions (i.e. evolutionary states) in the H–R diagram. The vertical lines indicate the values of the mean (blue continuous line), the mode (green dot-dashed line), and median (dashed red line). Top row, left panel: ill-determined (star SF1). Top row, right panel: one single peak (star SF12). Bottom row, left panel: age degeneracy leading to two peaks (star SF7). Bottom row, right panel: peculiar (star SF6). See discussion in the text.