Left: variation in the equivalent widths in [Å] of the ¹²CO 4-1 P27 line over the light cycle for the three 47 Tuc LPVs with the largest photometric amplitudes (V1, V2, V3, colour coded). Also shown is the corresponding variation with pulsation phase as derived for the dynamical model L4C025AP. Right: line-strength variation of the same line for one T_eff-sequence of hydrostatic models with log g = 0.0. The dotted lines mark the total range of equivalent widths measured for V1.