Measured cross-correlation function between the companion spectrum and the CO + H₂O model with and without the rescaling of the stellar lines described in Sect. 4.3.1. The difference between the two stems from when the reference spectrum containing the stellar and telluric lines was removed from the companion spectrum. The solid line is the resulting CCF from the approach we have taken in this paper, where we have scaled the stellar lines in the reference spectrum down by 15% to match the companion to star flux ratio at the companion position. The dashed line is the CCF for the case where the reference spectrum is removed from the companion spectrum without rescaling the stellar lines. The bottom panel shows the difference between the two.