Integration bands and derived excess light curve. Left: gray shaded areas show the integration bands with passband of 1 Å, 1.5 Å, and 3 Å, centered at the core of each sodium line. The red and blue intervals show the passbands of the reference bands for D₂ and D₁, respectively. Right: the raw excess light curve shown with the red circles for the 1.5 Å integration band inside the sodium D₂ line. Dashed vertical lines indicate times of ingress and egress.