EDP Sciences
Free Access
Volume 425, Number 3, October III 2004
Page(s) 997 - 1008
Section Stellar structure and evolution
DOI https://doi.org/10.1051/0004-6361:20048006

A&A 425, 997-1008 (2004)
DOI: 10.1051/0004-6361:20048006

New neighbours

III. 21 new companions to nearby dwarfs, discovered with adaptive optics
J.-L. Beuzit1, 2, D. Ségransan1, T. Forveille1, 2, S. Udry3, X. Delfosse1, 4, M. Mayor3, C. Perrier1, M.-C. Hainaut2, 5, C. Roddier6, F. Roddier6 and E. L. Martín6

1  Observatoire de Grenoble, Université J. Fourier, BP 53, 38041 Grenoble, France
2  Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Highway, Kamuela, HI 96743, Hawaii, USA
    e-mail: forveille@cfht.hawaii.edu
3  Observatoire de Genève, 1290 Sauverny, Switzerland
4  Instituto de Astrofisica de Canarias 38200 La Laguna, Tenerife, Canary Islands, Spain
5  Now at, Gemini Observatory, Southern Operations Center, c/o AURA Inc., Casilla 603, La Serena, Chile
6  Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, Hawaii, USA

(Received 15 June 2001 / Accepted 26 May 2004)

We present some results of a CFHT adaptive optics search for companions to nearby dwarfs. We identify 21 new components in solar neighbourhood systems, of which 13 were found while surveying a volume-limited sample of M dwarfs within 12 pc. We are obtaining complete observations for this subsample, to derive unbiased multiplicity statistics for the very-low-mass disk population. Additionally, we resolve for the first time 6 known spectroscopic or astrometric binaries, for a total of 27 newly resolved companions. A significant fraction of the new binaries has favourable parameters for accurate mass determinations. The newly resolved companion of Gl 120.1C was thought to have a spectroscopic minimum mass in the brown-dwarf range (Duquennoy & Mayor 1991), and it contributed to the statistical evidence that a few percent of solar-type stars might have close-in brown-dwarf companions. We find that Gl 120.1C actually is an unrecognised double-lined spectroscopic pair. Its radial-velocity amplitude had therefore been strongly underestimated by Duquennoy & Mayor (1991), and it does not truly belong to their sample of single-lined systems with minimum spectroscopic mass below the substellar limit.

We also present the first direct detection of Gl 494B, an astrometric brown-dwarf candidate. Its luminosity straddles the substellar limit, and it is a brown dwarf if its age is less than ~300 Myr. A few more years of observations will ascertain its mass and status from first principles.

Key words: stars: binaries: general -- stars: low-mass, brown dwarfs -- techniques: miscellaneous

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