Multiplicity of very low-mass objects in the Upper Scorpius OB association: a possible wide binary population

Abstract

We report the initial results of a VLT/NACO high spatial resolution imaging survey for multiple systems among 58 M-type members of the nearby Upper Scorpius OB association. Nine pairs with separations below 100 have been resolved. Their small angular separations and the similarity in the brightness of the components (DMagK <1 for all of them), indicate there is a reasonable likelihood several of them are true binaries rather than chance projections. Follow-up imaging observations with WHT/LIRIS of the two widest binaries confirm that their near-infrared colours are consistent with physical very low mass binaries. For one of these two binaries, WHT/LIRIS spectra of each component were obtained. We find that the two components have similar M6-M7 spectral types and signatures of low-gravity, as expected for a young brown dwarf binary in this association. Our preliminary results indicate a possible population of very low-mass binaries with semimajor axis in the range 100 AU 150 AU, which has not been seen in the Pleiades open cluster. If these candidates are confirmed (one is confirmed by this work), these results would indicate that the binary properties of very low-mass stars and brown dwarfs may depend on the environment where they form.

arXiv comment11 pages, 1 table, 7 figures, request high resolution copies to [email protected]

References in corpus (31)

• A Hipparcos census of the nearby OB associations
• Evolutionary models for low-mass stars and brown dwarfs: uncertainties and limits at very young ages
• Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble Space Telescope WPFC2
• The Formation Mechanism of Brown Dwarfs
• Detection of Nine M8.0-L0.5 Binaries: The Very Low Mass Binary Population and its Implications for Brown Dwarf and VLM Star Formation
• GaBoDS: The Garching-Bonn Deep Survey; IV. Methods for the Image reduction of multi-chip Cameras
• Multiplicity of Nearby Free-floating Ultra-cool Dwarfs: a HST-WFPC2 search for companions
• Infrared Spectra and Spectral Energy Distributions of Late-M- and L-Dwarfs
• Giant Planet Companion to 2MASSW J1207334-393254
• Evidence for a co-moving sub-stellar companion of GQ Lup
• Spectral Energy Distributions for Disk and Halo M--Dwarfs
• Hubble Space Telescope Observations of Binary Very-Low-Mass Stars and Brown Dwarfs
• Membership and Multiplicity among Very Low-Mass Stars and Brown Dwarfs in the Pleiades Cluster
• PPl 15: The First Brown Dwarf Spectroscopic Binary
• The First Discovery of a Wide Binary Brown Dwarf
• Discovery of Two Very Low-Mass Binaries: Final Results of an Adaptive Optics Survey of Nearby M6.0-M7.5 Stars
• Spectroscopic identification of DENIS-selected brown dwarf candidates in the Upper Scorpius OB association
• First determination of the dynamical mass of a binary L dwarf
• An HST/WFPC2 Survey for Brown Dwarf Binaries in the alpha Per and the Pleiades Open Clusters
• The Solar Neighborhood IX: Hubble Space Telescope Detections of Companions to Five M and L Dwarfs within 10 pc of the Sun
• An Adaptive Optics Survey of M8-M9 Stars: Discovery of 4 Very Low mass Binaries With at Least One System Containing a Brown Dwarf Companion
• The Decay of Accreting Triple Systems as Brown Dwarf Formation Scenario
• The Discovery of a Companion to the Very Cool Dwarf Gl~569~B with the Keck Adaptive Optics Facility
• Multiplicity at the Stellar/Substellar Boundary in Upper Scorpius
• The first wide ultracool binary dwarf in the field: DENIS-J055146.0-443412.2 (M8.5 + L0)
• A possible third component in the L dwarf binary system DENIS-P J020529.0-115925 discovered with the Hubble Space Telescope
• Very low-mass members of the Lupus 3 cloud
• A young binary Brown Dwarf in the R-CrA star formation region
• An L0 dwarf companion in the brown dwarf desert, at 30 AU
• Discovery of a widely separated binary system of very low mass stars
• Discovery of a Wide Low-mass Binary System in Upper Scorpius

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