χ²-based spectral fitting results of three representative targets based on the Sonora Diamondback atmospheric models. In the left panels, the observed IRTF/SpeX spectra (black) are compared with the best-fit model spectra (red), and the corresponding best-fit parameters are labeled. Fluxes within the broad water bands (shaded in gray) are masked in spectral fits. The right panels present the χ² values as a function of effective temperatures, with variations in symbol, color, and transparency indicating different values of ﹩\mathrm{log}(g)﹩, f_sed, and [M/H], respectively.