Stellar structure and oscillations of a 4.5 M_⊙ star from the single-star model (red) and the mass-accretion model (black). Left panels: Profiles of the buoyancy frequency, N (solid lines: left y axis), and the hydrogen mass fraction, X (dashed lines: right y axis). From top to bottom, the central hydrogen, X_c, values are 0.4, 0.3, 0.2, 0.1, and 0.01. Right panels: Corresponding period spacing patterns of l = 1 and l = 2 g modes.