Left panel: evolutionary tracks of the luminosity of the He-star companion (dash-dotted cyan line) and the orbital period of the binary system (solid orange line) during the whole mass-transfer process until the SN Ia explosion. Right panel: time evolution of the mass transfer rate (Ṁ_tr; dash-dotted cyan line) and the mass growth of a helium shell onto the WD (M_He; solid orange line). The vertical dotted lines give the moment of the SN explosion. The initial and final binary parameters (WD mass M_WD, companion mass M₂, and orbital period P) in our detailed binary calculations are shown in the plot and indicated with superscript letters ‘i’ and ‘f’, respectively.