Asymptotic giant branch and super-asymptotic giant branch stars: modelling dust production at solar metallicity

Abstract

We present dust yields for asymptotic giant branch (AGB) and super-asymptotic giant branch (SAGB) stars of solar metallicity. Stars with initial mass 1.5 M<SUB>☉</SUB> ≤ M<SUB>ini</SUB> ≤ 3 M<SUB>☉</SUB> reach the carbon star stage during the AGB phase and produce mainly solid carbon and SiC. The size and the amount of the carbon particles formed follows a positive trend with the mass of the star; the carbon grains with the largest size (a<SUB>C</SUB> ∼ 0.2 μm) are produced by AGB stars with M<SUB>ini</SUB> = 2.5-3 M<SUB>☉</SUB>, as these stars are those achieving the greatest enrichment of carbon in the surface regions. The size of SiC grains, being sensitive to the surface silicon abundance, remains at about a<SUB>SiC</SUB> ∼ 0.1μm. The mass of carbonaceous dust formed is in the range 10<SUP>-4</SUP>-5 × 10<SUP>-3</SUP> M<SUB>☉</SUB>, whereas the mass of SiC produced is 2 × 10<SUP>-4</SUP>-10<SUP>-3</SUP> M<SUB>☉</SUB>. Massive AGB/SAGB stars with M<SUB>ini</SUB> > 3 M<SUB>☉</SUB> experience hot bottom burning, which inhibits the formation of carbon stars. The most relevant dust species formed in these stars are silicate and alumina dust, with grain sizes in the range 0.1 < a<SUB>ol</SUB> < 0.15 μm and a_Al_2O_3 ∼ 0.07 μm, respectively. The mass of silicates produced spans the interval 3.4 × 10<SUP>-3</SUP> M<SUB>☉</SUB> ≤ M<SUB>dust</SUB> ≤ 1.1 × 10<SUP>-2</SUP> M<SUB>☉</SUB> and increases with the initial mass of the star.