2002A&A...384..452W

We derive an improved description of dust-driven stellar mass-loss for the cool winds of carbon-rich tip-AGB stars. We use pulsating wind models in which the mass loss is driven by radiation pressure on dust grains, for C-rich chemistry. From a larger set of these models, selected for representative dynamical (pulsational velocity amplitude Δv, period P) and chemical (the ε_C/ε_O abundance ratio) input parameters, an improved approximative mass-loss formula has been derived which depends only on the stellar parameters (effective temperature T_eff, luminosity L and mass M). Due to the detailed consideration of the chemistry and the physics of the dust nucleation and growth processes, there is a particularly strong dependence of the mass-loss rate {dot}(M) (in M_☉/yr) on T_eff: log{dot}(M)=8.86-1.95*logM/M_☉-6.81*logT/K+2.47*logL/L_☉. The dependence of the model mass-loss on the pulsational period has explicitly been accounted for in connection with the luminosity dependence, by applying an observed period-luminosity relation for C-rich Miras. We also apply the improved mass-loss description to our evolution models, and we revisit their tip-AGB mass-loss histories and the total masses lost, in comparison to our earlier work with a preliminary mass-loss description. While there is virtually no difference for the models in the lower mass range of consideration (M_i=1.0 to ≃1.3M_☉), we now find more realistic, larger superwind mass-loss rates for larger stellar masses: i.e., {dot}(M) between ≃0.4 and 1.0x10^–4M_☉/yr for M_i between 1.85 and 2.65M_☉, removing between 0.6 and 1.2M_☉, respectively, during the final 30000yrs on the tip-AGB.