Evolution of a 12 M_⊙ single-star model accreting material at different constant rates. Each line color corresponds to a specific accretion rate, as indicated in the figure legend. Accretion begins when the central hydrogen abundance drops below 0.5 and terminates once the star reaches critical rotation. Panel (a): Evolutionary tracks in the Hertzsprung–Russell diagram. Panels (b)-(h): Time evolution of key stellar properties. (b) stellar mass; (c) moment of inertia I (solid) and the logarithm of the ratio between the total angular momentum J and the surface angular velocity ω at the termination of mass transfer (dashed); (d) stellar radius; (e) gyration constant k²; (f) surface angular velocity (solid lines) and critical velocity (dashed lines); (g): ratio of surface angular velocity to critical velocity; (h): logarithm of the total angular momentum (solid line) and the total angular momentum required for the corresponding model to rotate at the critical velocities after TE is restored.