Same transmission spectra as shown in Fig. 5, but zooming into each line of the Na I doublet. The blue vertical dashed lines show the laboratory value of the Na I D2 or D1 line. In addition to the transmission spectrum of each line, we show the observed 2D maps around each particular line in the stellarrest frame. In these maps the spectra have been binned in orbital phase with a bin size of 0.002. In colour weshow the relative flux (blue and red correspond to negative and positive flux, respectively). The horizontal black dashed lines mark the four transit contacts.