Calculated energy flux from star and dust shell for solid SiO as absorber for spherical grains (dotted line) and using a distribution of particle shapes (CDE) (dashed line), subtracted by the black-body emission from the star for different mass-loss rates (in units M_⊙ yr^-1), and averaged emission profile of S-stars from Hony et al. (2009) (full lines). The line profile are scaled and shifted in arbitrary units such that the maxima and bottom line of observed and calculated profiles coincide and are of comparable height. In the case of Ṁ = 1 × 10^-6 M_⊙ yr^-1 a profile is added where additionally condensation of corundum is considered (dash-dotted line).