Profile differences δ_tΓ₁/Γ₁ = [Γ₁(t;Y_s+δY_s,ψ_CZ,ε)−Γ₁(t;Y_s,ψ_CZ,ε)]/Γ₁ obtained for a fixed value of δY_s = 0.05 and various sets (Y_s, ψ_CZ, ε) (the values used here are not the same as those in Fig. 6) around the reference = (0.255, −5, 0.015) as a function of the normalised acoustic depth t. (a) Dependence on 0.2 ≤ Y_s ≤ 0.35. (b) Dependence on −9 ≤ ψ_CZ ≤ −3. (c) Dependence on 0.01 ≤ ε ≤ 0.05.