Left: luminosity diagram for the C¹⁸O and ¹³CO lines. Translucent points are results of this work with grain-surface chemistry network The points are colored according to the disk mass of the model. Markers with errorbars are observations compiled in Zwicky et al. (2024) and from Ansdell et al. (2016). Right: luminosity diagram in the C¹⁸O and CO lines. All points are results of this work with grain-surface chemistry network and colored according to the R_c. Markers with errorbars are observations compiled in Zwicky et al. (2024).