Black: resolved line profiles of the SiO J = 6–5 and 5–4 molecular transitions observed by APEX and SEST in November 2014 and December 1992, respectively. Blue: predicted line profiles using L_∗ = 4500 L_⊙ (assumed throughout the modelling) and an abundance profile characterised by f₀ = 6.0 × 10^-5 relative to H₂ and e-folding radius r_e = 4 × 10¹³ cm with R_decl = 50 R_∗. Red: predicted line profiles using L_∗ = 2500 L_⊙ and the same abundance profile.