Observed and best-fit fluxes vs. wavelength for HD 198478 depending on the input parameters used in the simulations (see Table A.1 and text in Appendix A.2). Colours and symbols as in Figure A.1. Left: Best-fit models 470 kms⁻¹ for YHe = 0.2 (solid line; Sol. 1a) and YHe = 0.1 (magenta-dotted line; Sol. 1b). Right: Best-fit models for υ_∞ = 200 kms⁻¹ for YHe = 0.2 (solid line; Sol. 2a) and YHe = 0.1 (magenta-dotted line; Sol. 2b). The blue-dashed line in both plots shows how changes in YHe are reflected in the emission flux model.