Evolution of the total $\dot{\omega }$ (Newtonian plus general relativity) as a function of age. The red curve displays this evolution for solar-metallicity stars of 26.2 M_⊙ and 20.4 M_⊙ in a binary with e = 0.15 and P_anom = 3.95984 d according to the models of Claret (2019). The solid blue line shows our best estimate of $\dot{\omega }$ for BD+60° 497, and the hatched area provides the associated uncertainty. The brown and orange curves correspond to systems respectively with stars of masses 30.3 M_⊙ + 23.7 M_⊙ and 21.9 M_⊙ + 17.1 M_⊙.