C II λ1334.5 line in Visit D. Top panel: temporal evolution of the line flux averaged over the variable range −17 to 14 km s⁻¹ (top) and over its stable complementary range (bottom). Bottom panel: comparison between the stellar line averaged over the first, last, and second orbit (black profile), and the line averaged over the two most absorbed sub-exposures visible in the top panel (blue profile). The wavelength scale is in the expected star rest frame and has not been corrected for the 3.6 km s⁻¹ line shift (see text).