Hubble Space Telescope observations of binary very low mass stars and brown dwarfs

John E. Gizis, I. Neill Reid, Gillian R. Knapp, James Liebert, J. Davy Kirkpatrick, David W. Koerner, Adam J. Burgasser

Research output: Contribution to journalReview articlepeer-review

163 Scopus citations


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 17-3+4%, 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.

Original languageEnglish (US)
Pages (from-to)3302-3310
Number of pages9
JournalAstronomical Journal
Issue number6 1770
StatePublished - Jun 2003


  • Binaries: general
  • Stars: low-mass, brown dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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