Left: observed monochromatic velocity-to-amplitude ratio (1867 data points with error bars superimposed on the heavy black curve) as a function of wavelength for P₁ = 140.5 s. The predicted monochromatic ratios for different degree indices are also shown and labelled. The cgs unit convention is used for the y-axis. Right: similar to the left panel, but referring to the P₂ mode with 21 wavelength bins.