Spherical LTE model for the ³⁰SiO v = 1 J = 6–5 and ²⁹SiO v = 3 J = 6–5 lines. Panels a and b show a comparison between the model (black) and the spectra of the ³⁰SiO v = 1 line (red) observed over the stellar disk and off the limb of the disk (positions 2 and 6 in Fig. 4), respectively. Panels c and d show a comparison for the ²⁹SiO v = 3 line in the same manner. The velocity profile of the model is shown in panel e. Positive and negative velocities correspond to infall and outflow, respectively. Panel f shows the ²⁹SiO number density (assumed to be equal to that of ³⁰SiO) on the left ordinate and the gas temperature on the right ordinate. In panels e and f, the radius is shown in the units of R_cont (below) and R_⋆ (above).