Line-force multiplier, M(t), as a function of t for stars with T_eff and critical point density (log ρ_crit [g cm⁻³]) of 42 000 [K] and -12.79 (left) and 18 000 [K] and -14.52 (right). The line-force parameters Q, Q₀, and α at the critical point are 1043, 620, 0.73 (left) and 866, 834, 0.87 (right). Blue circles represent M(t) calculated from the entire line list, with the black line indicating the fit. Green and pink lines show M(t) calculated using only Fe lines and CNO lines, respectively. The vertical dashed orange line marks t_cri (see text).