Effective temperatures derived from the best χ² fits to BT-Settl models as a function of the spectral type assigned in the literature. Black circles correspond to the compilation by Leggett, red circles to the compilation of Keck LRIS spectra by Reid, orange circles to the NIRSPEC compilation, and blue ones to the IRTF compilation. The grey continuous line shows the T_eff-spectral type calibration by Stephens et al. (2009) from optical and infrared spectra. The dashed lines represent the same calibration ±250 K. The right-hand panel shows the residuals (T_{eff(predicted)} − T_eff(SLC)) with respect to the calibration.