The Effect of Pre-Main-Sequence Stars on Star Cluster Dynamics

We investigate the effects of the addition of pre-main-sequence evolution to star cluster simulations. We allowed stars to follow pre-main-sequence tracks that begin at the deuterium-burning birth line and end at the zero-age main sequence. We compared our simulations to ones in which the stars began their lives at the zero-age main sequence, and also investigated the effects of particular choices for initial binary orbital parameters. We find that the inclusion of the pre-main-sequence phase results in a slightly higher core concentration, lower binary fraction, and fewer hard binary systems. In general, the global properties of star clusters remain almost unchanged, but the properties of the binary star population in the cluster can be dramatically modified by the correct treatment of the pre-main-sequence stage.