The first wide ultracool binary dwarf in the field: DENIS-J055146.0-443412.2 (M8.5 + L0)

M. Billères , X. Delfosse (1) , J.-L. Beuzit (1) , T. Forveille (1) , L. Marchal (1) , E. L. Martín

1 LAOG - Laboratoire d'Astrophysique de Grenoble

We present observations of a new very low mass field binary, discovered during an infrared imaging survey of 250 DENIS L and very late-M dwarfs. DENIS-J055146.0-443412.2 is an M8.5 + L0 pair, with a physical separation of over 200 AU. This makes it the widest very low mass binary known in the field, by an order of magnitude. Such a system is fragile, and it would not have survived a close encounter with a third body. Its existence demonstrate that some very low mass stars/brown dwarfs form without ejection from a multiple system, or any other strong dynamical interaction.

M. Billères, X. Delfosse, J.-L. Beuzit, T. Forveille, L. Marchal, et al.. The first wide ultracool binary dwarf in the field: DENIS-J055146.0-443412.2 (M8.5 + L0). Astronomy and Astrophysics - A&A, 2005, 440, pp.L55-L58. ⟨10.1051/0004-6361:200500167⟩. ⟨hal-00398158⟩