Evolution of binary Model IV, in which the specific angular momentum of the accreted material is artificially reduced by a factor of ten once the accretor reaches critical rotation. Panel (a): evolution in the Hertzsprung–Russell diagram. (b): Mass-transfer and accretion history. (c): Stellar mass. (d): Ratio of surface angular velocity to the critical velocity. (e): Stellar radius. (f): Gyration constant.