Spectrum of CVSO 30 c as extracted from the spectral deconvolution-corrected cube in the right panel of Fig. 3. Top: the spectrum in resolution 700 (black) is shown after binning of the original extracted spectrum in resolution 1500 (green). The best-fitting Drift-Phoenix model of Helling et al. (2008) is shown in red, fitting both the individually normalised H and K spectra. This type of normalisation was necessary because the redder colour of the models, in comparison to the unusually blue nature of CVSO 30 c, would steer the best-fitting model to higher temperatures, which would prevent fitting the individual features in H and K-band. The best-fitting model (red) corresponds to 1600 K, surface gravity log g 3.6 dex, metallicity [M/H] 0.3 dex, and 0.19 mag of visual extinction. Bottom: absolute value of the difference between spectrum and model from the top panel (black) versus noise floor at the corresponding position (green).