1σ contour plots of the χ² Drift-Phoenix model fit to the spectrum shown in Fig. 4. Contour plot in extinction vs. effective temperature (top), surface gravity log g vs. effective temperature (centre) and metallicity [M/H] vs. effective temperature (bottom). The fit shows a best fit at 1600 K, low extinction of 0.19 mag, higher values becoming increasingly less likely, and a best fit at log g 3.6. While all surface gravities seem to be almost of equal probability, a high surface gravity foreground brown dwarf can be excluded from the shape of the H-band in Fig. 6. Although the young planetary models differ in photometric colours, this could be because of a not yet fully understood change in the cloud properties at the L-T transition that is indicated by the change in brightness of the L-T transition with age of the system, which we show in Fig. 11.