Percentage of extra absorption as shown in Z19, Fig. 5 for the wavelength area of the sodium doublet. Grey points are at HARPS resolution, black points binned by 20. Left panel: transmission spectrum of WASP-127b created from the first two transits, that were available to the authors of Z19. Right: same dataset is taken and the core of the stellar sodium doublet masked out (we masked ± 3.5 kms⁻¹ of each line centre, amounting to roughly 8–9 bins per spectrum). In blue is a Gaussian fit on the grey data for visualisation. In line with Z19, we did not apply any spectra selection. The lower noise in comparison with Z19 can be attributed to our automatic correction for cosmics and different telluric corrections.