Results of the χ² fits to the CO absorption in Orion with the high-resolution infrared spectrum of α Ori (Wallace & Hinkle 1996). In the left side panel we show the Δχ² curves as a function of the ΔV used to smooth the library spectrum. On the right we show the comparison between the observed spectrum in each of the three regions (full lines) with the best-fitting photosphere (dashed lines, corresponding to the Δχ² minima in the left-hand side plot).