Best fit synthetic spectrum from BT-Settl13 models (black) using parameters derived from MCMC analysis of the complete Y JH spectrum (excluding the terrestrial water absorption band) from S4 extractions of the P1640 spectrum of GJ 758 B (gray markers and error bars). 100 spectra were randomly chosen from the posterior distributions of the MCMC calculations to represent the range of model fits that are allowed within 1 − σ uncertainty for the spectrum. The best fit parameters, 741 K/4.3 dex (cgs) for the Y JH spectrum, are the 50% quantiles of the effective temperature and surface gravity parameters from the MCMC posterior distributions (see Figure 9. The BT-Settl13 spectra with parameters determined from YJ and H fits only are shown in red and blue, respectively.