The dust sublimation surface in our Class 0/I models (outer red circle) and our Class II model (inner green circle), for the grain size distribution and mixture of silicates and graphite proposed by Mathis et al. (1977). The wind slow magnetosonic surface (denoted SMS) is superimposed as well as three flow lines (orange dotted lines), including the innermost one launched from 0.07 AU. The stellar parameters are T_⋆ = 4000 K and R_⋆ = 3   R_⊙, while the hot spot temperature and coverage fraction are T_hs = 10   000 K, and δ_hs = 0.032 (Class 0/I) and 0.0032 (Class II).