Top: frequency spectrum corresponding to the observed modes (dashed lines). All other spectra (solid lines) are based on theoretical models along a 1.5 M_⊙ evolution sequence with large separations Δν around the observed value. Theoretical frequencies have been decreased by a constant factor to improve visual comparison. Different colours correspond to different degrees as in Fig. 6: ℓ = 0 (black), ℓ = 1 (blue), ℓ = 2 (red), and ℓ = 3 (pink). The amplitudes of the theoretical modes have been scaled to 1/ relative to the radial modes except for the ℓ = 3 modes, which in addition contain a 0.3 factor (to improve the visibility). The numbers on the left are the values of the large separation Δν in μHz. Grey shaded regions are done to guide the eye.