Schematic of R 144 as seen during primary inferior conjunction (ϕ ≈ −0.026). The primary (filled blue circle) and secondary (filled teal circle) are plotted to scale with their relative separation. The thick red line indicates the WWC cone. The line-forming regions of several diagnostic lines for the primary star, as calculated from our tailored model atmosphere (Sect. 3.3), are denoted. The line-forming regions of the secondary star are comparable.