(S/N) K_p – V_rest maps. These maps are built by cross-correlating a single-species model of H₂O with data of KELT-8 b (left panel) and KELT-23 Ab (right panel), as described in the text. The maps are computed dividing the CCF values by the standard deviation of the noise far (| V_rest | ≥ 25 km s⁻¹ ) from the peak. The horizontal (vertical) white dashed lines represent the expected K_p ( V_rest) of the atmospheric signal. The black ‘×’ marks denote the cross-correlation maximum in each plot.