Transmission light curves of WASP-7 b around the Na i D₂ line. Top panel: Observation transmission light curves (gray) and modeled transmission light curves of the RM and the CLV (dotted blue line) for the 0.45 Å integration band centered on the Na i D₂ line. The dashed red line is the absorption component using a box model, and the gray shades denote its 1σ uncertainty. The solid black line is the best-fit combined model and the red points show binning by a factor of ten. Bottom panel: Residuals for binned and unbinned data. Green shades indicate out-of-transit time throughout.