Average derivative of the electron molar fraction with respect to the ¹²C molar fraction during carbon simmering, as a function of density for different carbon fusion rates: CF88 (black asterisks), LER-1.5-0.1-1.0 (blue triangles), LER-1.5-0.001-1.0 and LER-1.5-10.-1.0 (green stars), and LER-1.5-0.1-5.0 and LER-1.5-0.1-0.2 (red and magenta circles, respectively). All the models shown in this panel were computed at constant density. The models with the extreme resonance strengths were computed only at ρ = 2 × 10⁹ g cm^-3.