Red component of the metastable helium triplet of model S2^*, calculated from cells that exceed a specific threshold in optical depth (see Fig. B.1). The velocity axis is centered around the peak of the red component, which consists of two unresolved spectral lines, marked by the vertical dotted lines. The three peaks in the spectrum correspond to the trailing stream (1, blueshifted), the region near the planet ( 2, almost no shift), and the leading stream (3, redshifted). For completeness, we also include the full He I 1083 nm spectrum, which incorporates the blue component of the triplet, shown with a dotted gray line.