The intense production of silicates during the final AGB phases of intermediate mass stars

Context. The formation of silicates in circumstellar envelopes stars evolving through the asymptotic giant branch (AGB) is still highly debated given uncertainties affecting stellar evolution modelling, description dust process, and capability silicate grains to accelerate outflows via radiation pressure. Aims. We study winds intermediate mass ( M ≥ 4 ⊙ ) solar metallicity while AGB phase. tested different treatments mass-loss mechanism by this class stars, with aim assessing their contribution general enrichment interstellar medium galaxies and, on more grounds, budget Universe. Methods. consider a sub-sample whose spectral energy distribution (SED) characterised deep absorption features at 10 μm 18 μm, which can be regarded as providing most relevant silicates’ production across Results from modelling were used fit observed SED reproduce, same time, detected pulsation periods derived surface chemical composition. This analysis leads derivation tight constraints rates experienced these sources during final stages. Results. Two out four investigated are interpreted currently undergoing hot bottom burning (HBB), phases close stage when rate largest. remaining two likely very phases, after HBB was turned off gradual consumption convective mantle. Mass-loss order 1 × −4 yr −1 2 required looking for consistency observational evidence. These results indicate need revision yields found ∼3 times higher than previously determined.