On the frequency of close binary systems among very low-mass stars and brown dwarfs
Abstract
We have used Monte Carlo simulation techniques and published radial velocity surveys to constrain the frequency of very low-mass star (VLMS) and brown dwarf (BD) binary systems and their separation (a) distribution. Gaussian models for the separation distribution with a peak at a = 4 au and 0.6 =< sigma(log(a/au)) =< 1.0 correctly predict the number of observed binaries, yielding a close (a<2.6 au) binary frequency of 17-30 per cent and an overall VLMS/BD binary frequency of 32-45 per cent. We find that the available N-body models of VLMS/BD formation from dynamically decaying protostellar multiple systems are excluded at >99 per cent confidence because they predict too few close binary VLMS/BDs. The large number of close binaries and high overall binary frequency are also very inconsistent with recent smoothed particle hydrodynamical modelling and argue against a dynamical origin for VLMS/BDs.
Keywords
Cite
@article{arxiv.astro-ph/0507177,
title = {On the frequency of close binary systems among very low-mass stars and brown dwarfs},
author = {P. F. L. Maxted and R. D. Jeffries},
journal= {arXiv preprint arXiv:astro-ph/0507177},
year = {2009}
}
Comments
Accepted for publication in MNRAS letters. 5 pages, 2 figures