Total cross-correlation signal from carbon monoxide in transmission spectrum of HD 189733 b, as function of stellar removal applied to data. Left panel: uncorrected spectra show a candidate signal at expected planet maximum orbital velocity (K_P ~ 151 km s⁻¹, white dashed lines), but also significant stellar contamination at all values of K_P from uncorrected CO stellar lines. Middle panel: application of a parametric 1D stellar model partially mitigates the problem and allows recovery of the CO signal at 5σ (Brogi et al. 2016). There is, however, still a residual stellar signal that hinders detection. Right panel: application of phase-resolved 3D stellar models accounting for the geometry of transit (this work and Flowers et al. 2019) allows us to unambiguosly detect the planet CO signal at > 7σ of confidence level.