Rejuvenation of early (panel a) and late (panel b) Case A accretors. The rejuvenation is quantified as the difference of the average helium mass fraction ⟨Y⟩ of the accretors at the terminal-age main sequence (TAMS) relative to that of single stars. The relative differences are plotted as a function of mass at the TAMS, M_TAMS. Negative differences mean that the accretors have burnt less hydrogen into helium compared to single stars, that is they have less massive convective cores. This is a sign that accretors did not (fully) adjust their structure to the new total mass after accretion, that is they did not (fully) rejuvenate.