Star-disk interactions in small N clusters: How to form binary stars
We investigate the effect of circumstellar disks on the dynamical evolution of a small cluster of protostars formed by ‘prompt initial fragmentation’. In particular we study how the presence of disks affects the resultant mass components of binaries formed in the cluster. We find that when the stars are assigned circumstellar disks the occurrence of lower mass stars in binaries is greatly increased compared with diskless simulations. This is due to the fact that disks both increase the number of binaries formed and also randomise the selection of secondary mass companions to each primary. For a cluster of 10 stars with massive disks the predicted binary fraction is in good agreement with observations. We also find that disks boost the number of triple and quadruple systems formed, and suggest that the eventual disruption of the less hierarchical multiples might account for the excess of binaries among pre-main sequence stars.
KeywordsMass Function Massive Star Initial Mass Function Lower Mass Star Tauri Star
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