EDP Sciences
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Volume 439, Number 2, August IV 2005
Page(s) 565 - 569
Section Galactic structure, stellar clusters and populations
DOI http://dx.doi.org/10.1051/0004-6361:20052654

A&A 439, 565-569 (2005)
DOI: 10.1051/0004-6361:20052654

Limits on the primordial stellar multiplicity

S. P. Goodwin1 and P. Kroupa2, 3

1  School of Physics & Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3YB, UK
    e-mail: Simon.Goodwin@astro.cf.ac.uk
2  Sternwarte, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
3  Rhine Stellar Dynamical Network

(Received 7 January 2005 / Accepted 10 May 2005 )

Most stars - especially young stars - are observed to be in multiple systems. Dynamical evolution is unable to pair stars efficiently, which leads to the conclusion that star-forming cores must usually fragment into $\geq $2 stars. However, the dynamical decay of systems with $\geq $3 or 4 stars would result in a large single-star population that is not seen in the young stellar population. Additionally, ejections would produce a significant population of close binaries that are not observed. This leads to a strong constraint on star formation theories that cores must typically produce only 2 or 3 stars. This conclusion is in sharp disagreement with the results of currently available numerical simulations that follow the fragmentation of molecular cores and typically predict the formation of 5-10 seeds per core. In addition, open cluster remnants may account for the majority of observed highly hierarchical higher-order multiple systems in the field.

Key words: stars: formation -- binaries: general -- stars: low-mass, brown dwarfs

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© ESO 2005