Orbital period (top panel) and secondary mass (bottom panel) as a function of primary mass. The blue, green, and red solid lines correspond to the best-fit binary sequences that reproduce HMXBs that resemble M33 X-7, Cyguns X-1, and LMC X-1, respectively. The properties of the observed systems are marked with blue, red, and green squares for M33 X-7, Cygnus X-1, and LMC X-1, respectively. The arrow on the top panel represents the direction of the evolution.