Top panel: efficiency per grain radius Q_acc/a_gr, in the small particle limit, as a function of wavelength for a selection of dust species. The dashed lines show the power law fit according to Eq. (20) and the shaded area indicates the wavelength region for which the optical data is fitted. Lower panel: normalized flux of the hydrostatic initial model (black) and the Planck function for T_eff = 2800   K (red). Due to absorption by TiO molecules in the visual the flux of the initial model is very non-Planckian in this wavelength region.