Astron. J., 125, 3302-3310 (2003/June-0)
Hubble space telescope observations of binary very low mass stars and brown dwarfs.
GIZIS J.E., REID I.N., KNAPP G.R., LIEBERT J., KIRKPATRICK J.D., KOERNER D.W. and BURGASSER A.J.
Abstract (from CDS):
We present analysis of Hubble Space Telescope (HST) images of 82 nearby field late M and L dwarfs. We resolve 13 of these systems into double M/L dwarf systems and identify an additional possible binary. Combined with previous observations of 20 L dwarfs, we derive an observed binary fraction for ultracool dwarfs of 17+4–3%, where the statistics included systems with separations in the range 1.6-16 AU. We argue that accounting for biases and incompleteness leads to an estimated binary fraction 15%±5% in the range 1.6-16 AU. No systems wider than 16 AU are seen, implying that the wide companion frequency is less than 1.7%; the distribution of orbital separation is peaked at ∼2-4 AU and differs greatly from the G dwarf binary distribution. Indirect evidence suggests that the binary fraction is ∼5%±3% for separations less than 1.6 AU. We find no evidence for differences in the binary fraction between stellar late M and L dwarfs and substellar L dwarfs. We note, however, that the widest (greater than 10 AU) systems in our sample are all of earlier (M8-L0) spectral type; a larger sample is needed to determine if this is a real effect. One system with a spectral type of L7 has a secondary that is fainter in the HST F814W filter but brighter in F1042M; we argue that this secondary is an early T dwarf.
Stars: Binaries: General - Stars: Low-Mass, Brown Dwarfs
VizieR on-line data:
<Available at CDS (J/AJ/125/3302): table1.dat table2.dat>
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