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 journalArticle

143 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

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Gizis, J. E., Reid, I. N., Knapp, G. R., Liebert, J., Kirkpatrick, J. D., Koerner, D. W., & Burgasser, A. J. (2003). Hubble Space Telescope observations of binary very low mass stars and brown dwarfs. Astronomical Journal, 125(6 1770), 3302-3310.