Evolution of detailed binary parameters during the rapid Case A mass transfer episode. Panel (a1): Entropy profile versus mass coordinate for the mass-losing star. Panel (a2): Corresponding profile for the mass-gaining star. panels (b1) and (b2): Luminosity profiles for both components. Panels (c1) and (c2): Temperature profiles. Panels (d1) and (d2): Density profiles. Panels (e1) and (e2): Mean molecular weight profiles. Panels (f1) and (f2): Hydrogen energy production rate, ϵ_H, profiles for both components.