Best fits for the data of Bands 3, 4, 7, and 9 using the dusty disc (Zhu et al. 2018) model and the simple dusty disc model (described in Sect. 3.2) are shown as the solid orange and light grey lines, respectively. For the dusty disc, we find that the best fit parameters of the model are $\log ({\dot{M}}_{\mathrm{p}}/(M_{\mathrm{J}\mathrm{u}\mathrm{p}}/\mathrm{y}\mathrm{r}))=-{9.04}_{-2.75}^{+0.46}$ and $\log (\alpha )=-{5.21}_{-2.82}^{+0.53}$ at 1 σ. The resulting spectral index is 2.35 and has a minimum reduced χ² of 6.50. For the simpler dusty disc model, we find that the best fit parameter is $\log (\gamma )=-{2.67}_{-0.05}^{+0.04}$. The resulting spectral index is 3 and has a minimum reduced χ² of 14.61. Here the reduced χ² is the χ² divided by the number of points (data) minus the number of degrees of freedom in the model.