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

Abstract: 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 $\tau_{\rm v}$ between 3 and 3.5 half-mass relaxation times. By the means of numerical models, here we investigate the role of the primordial binary population on the loss of primordial mass segregation. We found that $\tau_{\rm v}$ does not seem to depend on the binary star distribution, yielding $3 < \tau_{\rm v} / t_{\rm rh} < 3.5$. 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.