Evolutionary tracks of primary and secondary components obtained from our simulations. (a) HRD with the evolutionary tracks of primary components. The grey area corresponds to the region occupied by the full set of 20 000 tracks, while a subsample of 100 randomly selected tracks is indicated with coloured points connected by solid black lines. Each point represents one saved MESA model. The colour-coding reflects the central hydrogen abundance. The effective temperature of the bi-stability jump (T_eff ≈ 26 000 K) is marked with the vertical dashed line. The abrupt change in the behaviour of some evolutionary tracks after crossing the bi-stability jump region is due to a significant change in the wind mass-loss rate. (b) Same as panel a, but for a set of secondary components. We note the difference in the ranges of the two axes in panels a and b. More details are discussed in the main text.