Intercepts (dark grey, left axis) and slopes (pink, right axis) of linear fits in log α versus Δν for RGB models as a function of mass. The points show the mean slope and intercept of fits for 1000 perturbations in which we perturbed both ν_max and the individual frequencies within their uncertainties. The vertical bars indicate the spread in the results of these 1000 perturbations. The points connected by a solid line show the results of fits in which both the slope and the intercept were free parameters. The dashed lines connect points for fits with a fixed slope. See text for more details and Fig. C.1 for the fits to the different masses.