Schematic view of the envelope of W Hya. The radii of the different structures are given to scale. The radius of the star and the scattering shell are 1.8 AU and 3.6 AU. The inner radius of the GBDS is not constrained by our model and is assumed to be 3.1 AU (1.7 R_⋆) for the small amorphous Al₂O₃ grains. The inner radius of the silicate envelope shown is the lower limit of 40 AU given by Zhao-Geisler et al. (2011).