Same plot as in Fig. 25. Top panel: absorption over the range −230 to −175 km s^-1 (orange symbols) and −175 to −140 km s^-1 (blue symbols) for a simulation of atmospheric escape from HD 189733b (escape rate Ṁ = 2 × 10⁹ g s^-1; ionizing flux F_ion = 3  F_⊙; stellar wind with velocity V_wind = 200 km s^-1, temperature T_wind = 3 × 10⁴ K and density n_wind = 2 × 10⁴ cm^-3). Vertical dashed lines show the beginning and end of STIS transit and post-transit observations. An absorption signature was detected by Lecavelier des Etangs et al. (2012) in the blue wing of the Lyman-α line between −230 and −140 km s^-1. Bottom panel: views of the gas in the orbital plane that moves in the velocity intervals described above (orange and light blue), and between −140 km s^-1 and 40 km s^-1 (deep blue). The cometary tail is mostly composed of high-velocity atoms accelerated by interactions with the stellar wind. These atoms keep their Maxwellian velocity distribution as they move farther away from the planet. As a result, the relative absorption over any velocity interval is roughly constant with time. The relative level of the absorption depends on the proportion of atoms in the Maxwellian distribution for a given velocity interval.