Secondary mass and χ_red²-minima as a function of primary mass from the models with the condition of equal metallicity for the components Z₁ = Z₂ (Case A1). The color bar indicates the respective χ_red²-minima on a logarithmic scale. The residuals were calculated with enforcing M₁ ≥ M₂; the gray area represents the respective space where no χ_red² is calculated due to this condition. The seismic solution, including its error bars from BKP18, is given in black, the absolute χ_red²-minimum is given in magenta triangle, and the green line represents the spectroscopic mass ratio of q = 1.015.