Change in orbital period and eccentricity between t₀ and t_TAMS (upper row), and between t₀ and the end of the core helium burning t_He,end (lower row). The colour-scale shows the ratio between the number of ProCeps (at t_TAMS) or Cepheids (at t_He,end) and the number of ProCeps at t₀, which are located at the nearby position in the log₁₀(P) − e plane. Values larger (lower) than 1 indicate that the number of ProCeps or Cepheids increased (decreased) since t₀. The dashed and dotted white lines show the period threshold for coalescence (at log₁₀(P[days]) = 2.6) and the upper limit on the birth period distribution (log₁₀(P[days]) = 6.7), respectively. The black line shows the maximum allowed eccentricity for given orbital period at t₀ (assuming m₁ + m₂ = 9 M_⊙ and stellar radius of R₁ = 5 R_⊙). The absence of binaries with log₁₀(P[days]) ≲ 2.6 at t_He.end is due to stellar collisions. The depletion of binaries with log₁₀(P[days]) ≳ 3 and e ≲ 0.5 (the white rectangle with an indication of eccentricity evolution) seen already at the t_TAMS in the standard model is due to dynamical encounters with other cluster members (the depletion is absent in the control model). The binaries with log₁₀(P[days]) ≳ 6.7 in the standard model (and absent in the control model) are mostly outer orbits in triples.