Top: common-mode corrected exoplanet spectra with propagated 1-σ error bars as described in Sect. 2.2. The transit spectrum extraction in blue is referred to as the nominal extraction. Bottom: same spectra, except for the nominal transit spectrum which has been re-interpolated by the measured positional shift (computed in Sect. 2.4). The systematic spectral slope is largely removed but residual noise is still clearly present in the spectrum in the form of variation between spectral bins with amplitude larger than the expected errors or planet signal.