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 tau(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 tau(v) does not depend on the binary star distribution, yielding 3 < tau(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.