Top panel: evolutionary tracks at Z_init = 0.014 in the Δν/ν_max versus log (ν_max) diagram. For clarity, only the 0.5, 1.1, and 3.5 M_⊙ tracks are plotted, as labeled next to the tracks. The main sequence is shown in thicker lines. The ZAMS is located on the right of each track. Reference points are indicated with symbols as in Fig. 1. The dashed line is a straight line passing through the ZAMS and the first MS hook of the 3.5 M_⊙ star, given by Eq. (5). The frequencies are expressed in μHz. Bottom panel: same as top panel, but for the residual of Δν/ν_max with respect to the straight line in the top panel.