Comparison between envelope parameters related with the mass-loss mechanism. Upper: Distribution of the β parameter, defined as the ratio of the outflow to the stellar radiation momentum (β = Ṁ V_exp c/L_bol, Sect. 6.4). Centre: relationship between stellar pulsation period (P) and β. Lower: relationship between Ṁ and L_bol; the solid line represents the single-scattering limit in the case V_exp = 10 km s⁻¹ (see Groenewegen & Sloan 2018) and the dashed line the best linear fit to our dataset. The colours and shapes of the markers are the same as in Fig. 7. Grey markers represent AGB stars with Ṁ and L_bol values recompiled from Danilovich et al. (2015) (circles: O-rich AGB stars, squares: S stars, and crosses: C-rich AGB stars).