Letter to the Editor

Five new very low mass binaries

¹ Laboratoire d'Astrophysique de Grenoble, BP 53, 38041 Grenoble Cedex, France e-mail: Guillaume.Montagnier@obs.ujf-grenoble.fr
² Observatoire de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
³ Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Highway, Kamuela, HI 96743, Hawaii, USA
⁴ European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁵ Laboratoire d'Astrophysique de Toulouse et Tarbes, BP 826, 65008 Tarbes Cedex, France
⁶ ONERA-DOTA, BP 72, 29 avenue de la Division Leclerc, 92322 Châtillon Cedex, France
⁷ Laboratoire d'Études Spatiales et d'Instrumentation Astrophysique, 92195 Meudon Cedex, France

Received: 26 July 2006
Accepted: 12 October 2006

Abstract

We report the discovery of companions to 5 nearby late M dwarfs (>M5), LHS1901, LHS4009, LHS6167, LP869-26 and WT460, and we confirm that the recently discovered mid-T brown dwarf companion to SCR1845-6357 is physically bound to that star. These discoveries result from our adaptive optics survey of all M dwarfs within 12 pc. The new companions have spectral types M5 to L1, and orbital separations between 1 and 10 AU. They add significantly to the number of late M dwarfs binaries in the immediate solar neighbourhood, and will improve the multiplicity statistics of late M dwarfs. The expected periods range from 3 to 130 years. Several pairs thus have good potential for accurate mass determination in this poorly sampled mass range.