Lyα absorption in GD 40 and G241-6. The black lines represent models with the "final" abundances given in Tables 3 and 4 without any interstellar contribution. The dashed pink lines represent models with [H]/[He] = −6.16 and column densities of interstellar hydrogen of 1 × 10 ²⁰ cm ⁻² and 3 × 10 ¹⁹ cm ⁻² toward GD 40 and G241-6, respectively (see Section 3.2). For clarity, the spectrum for GD 40 is offset by 1.5 × 10 ⁻¹⁴ erg s ⁻¹ cm ⁻² Å ⁻¹. Because the data are shifted into the star's frame of reference, the day glow emission lines for the two stars are displaced.