An adaptive optics survey of M8-M9 stars: Discovery of four very low mass binaries with at least one system containing a brown dwarf companion

Laird M Close, Nick Siegler, Dan Potter, Wolfgang Brandner, James Liebert

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

Use of the highly sensitive Hokupa'a/Gemini curvature wave-front sensor has allowed, for the first time, direct adaptive optics guiding on M8-M9 very low mass (VLM) stars. An initial survey of 20 such objects (spectral type = M8-M9) discovered four binaries. Three of the systems have separations of less than 4.2 AU and similar mass ratios (ΔK < 0.8 mag; 0.85 < q < 1.0). One system, however, did have the largest mass ratio (ΔK = 2.38 mag) and separation (14.4 AU) yet observed for a VLM star with a brown dwarf companion. Based on our initial flux-limited (Ks < 12 mag) survey of 20 M8-M9 stars over 14h26m < R.A. < 4 h30m from the sample of Gizis et al., we find a binary fraction in the range of 14%-24% for M8-M9 binaries with separations of less than 3 AU. This is likely consistent with the 23% ± 5% measured for more massive (M0-M6) stars over the same separation range. It appears that M8-M9 binaries have a much smaller semimajor axis distribution peak (∼4 AU; with no systems wider than 15 AU) compared with M and G stars that have a broad peak at larger ∼30 AU separations.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume567
Issue number1 II
DOIs
StatePublished - Mar 1 2002

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adaptive optics
stars
mass ratios
G stars
M stars
wave fronts
curvature
sensor
sensors

Keywords

  • Binaries: general
  • Instrumentation: adaptive optics
  • Stars: evolution
  • Stars: formation
  • Stars: low-mass, brown dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

An adaptive optics survey of M8-M9 stars : Discovery of four very low mass binaries with at least one system containing a brown dwarf companion. / Close, Laird M; Siegler, Nick; Potter, Dan; Brandner, Wolfgang; Liebert, James.

In: Astrophysical Journal, Vol. 567, No. 1 II, 01.03.2002.

Research output: Contribution to journalArticle

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