Schematic profile formation of a blended inverse P Cygni profile. Panel a: the supersonic (≈50 km s⁻¹) descending atmospheric layers produce a radiative emission centered on 0 km s⁻¹ (blue curve).This profile is blended with photospheric redshifted (≈15 km s⁻¹) absorption (orange curve) resulting in an apparently weak blueshifted emission. Panel b: in long-period Cepheids, a component centered on 0 km s⁻¹ is attributed to a CSE (green) and causes the appearance of a double absorption profile.