Primordial mass segregation of star clusters: The role of binary stars

Observational results of young star-forming regions suggest that star clusters are completely mass segregated at birth. As a star cluster evolves dynamically, these initial conditions are gradually lost. For star clusters with single stars only and a canonical IMF, it has been suggested that traces of these initial conditions vanish at τ_v between 3 and 3.5 half-mass relaxation times. Here, by means of numerical models, we investigate the role of the primordial binary population on the loss of primordial mass segregation. We found that τ_v does not depend on the binary star distribution, yielding 3 < τ_v / t_rh < 3.5. We also conclude that the completely mass segregated clusters, even with binaries, are more compatible with the present-day ONC than the non-segregated ones.