Similar to Fig. 5, but now with C¹⁷O, ¹³C¹⁸O and ¹³C¹⁷O on the vertical axes and ¹²CO on the horizontal axis. The black dots mark HD 100546 observations of C¹⁷O J = 3–2 (Booth, A., priv. comm.), HD 163296 observations of ¹³C¹⁷O J = 3–2 from Booth et al. (2019), HD 31648 observations of ¹³C¹⁸O J = 3–2 from Loomis et al. (2020), and HD 142527 observations of ¹³C¹⁸O J = 3–2 by Temmink et al. (2023). Similar to Fig. 5 probability density curves are shown along the vertical and horizontal axes to indicate where most of the models of a particular mass reside.