Distributions of the absolute values of phase velocity V_ph of waves, modulating the stellar activity pattern, estimated with Eq. (3) for the drift rates, D₁ and D₂, from Table A.1, versus the log of the stellar effective temperature T. (a) the positive drifts (squares); (b) the negative drifts (rhombi). The labeled curves depict the theoretic predictions for the different waves in photospheres of the main sequence stars, according to the dispersion relations from Lou (2000) and stellar parameters from the models of fast rotators in Amard et al. (2019) with maximal surface gravity. Panel (c) shows the range of the actual values (grey) of the small parameter β_o = 2Ω/R_*, used for the solving of the dispersion equations in β-plane approximation for the considered shallow-fluid wave modes.