Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics

Abstract

We present the discovery of 2MASS J21321145+1341584AB as a closely separated (0.066") very low-mass field dwarf binary resolved in the near-infrared by the Keck II Telescope using laser guide star adaptive optics. Physical association is deduced from the angular proximity of the components and constraints on their common proper motion. We have obtained a near-infrared spectrum of the binary and find that it is best described by an L5+/-0.5 primary and an L7.5+/-0.5 secondary. Model-dependent masses predict that the two components straddle the hydrogen burning limit threshold with the primary likely stellar and the secondary likely substellar. The properties of this sytem - close projected separation (1.8+/-0.3 AU) and near unity mass ratio - are consistent with previous results for very low-mass field binaries. The relatively short estimated orbital period of this system (~7-12 yr) makes it a good target for dynamical mass measurements. Interestingly, the system's angular separation is the tightest yet for any very low-mass binary published from a ground-based telescope and is the tightest binary discovered with laser guide star adaptive optics to date.

10 pages, 3 figures; accepted for publication to AJ

References in corpus (33)

• The USNO-B Catalog
• A Non-Gray Theory of Extrasolar Giant Planets and Brown Dwarfs
• A Method of Correcting Near-Infrared Spectra for Telluric Absorption
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• Sixty-seven Additional L Dwarfs Discovered by the Two Micron All Sky Survey (2MASS)
• A Unified Near Infrared Spectral Classification Scheme for T Dwarfs
• L' and M' Photometry of Ultracool Dwarfs
• Characterization of M,L and T dwarfs in the Sloan Digital Sky Survey
• Meeting the Cool New Neighbors V: A 2MASS-Selected Sample of Ultracool Dwarfs
• The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy
• Spectroscopic Properties of Cool Stars in the SDSS: An Analysis of Magnetic Activity and a Search for Subdwarfs
• Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey
• Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field
• The Mauna Kea Observatories Near-Infrared Filter Set. I: Defining Optimal 1-5 $\mu$m Bandpasses
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• The First Substellar Subdwarf? Discovery of a Metal-poor L Dwarf with Halo Kinematics
• Binaries and the L Dwarf/T Dwarf Transition
• SDSS J1534+1615AB: A Novel T Dwarf Binary Found with Keck Laser Guide Star Adaptive Optics and the Potential Role of Binarity in the L/T Transition
• The Age of AB Dor
• A search for binary systems among the nearest L dwarfs
• Multiplicity Amongst Wide Brown Dwarf Companions to Nearby Stars: Gliese 337CD
• Dynamical Masses of the Binary Brown Dwarf GJ 569Bab
• The Substellar Mass Function: A Bayesian Approach
• The orbit of the brown dwarf binary Gl 569B
• 2MASS J05185995-2828372: Discovery of an Unresolved L/T Binary
• Kelu-1 is a Binary L Dwarf: First Brown Dwarf Science from Laser Guide Star Adaptive Optics
• Discovery of a Second L Subdwarf in the Two Micron All Sky Survey
• First determination of the dynamical mass of a binary L dwarf
• SDSS J042348.57-041403.5AB: A Brown Dwarf Binary Straddling the L/T Transition
• LSR1610-0040: the first early-type L subdwarf
• Discovery of a 0.15" Binary Brown Dwarf 2MASSJ 1426316+155701 With Gemini/Hokupa'a Adaptive Optics
• The Schizophrenic Spectrum of LSR 1610-0040: a Peculiar M Dwarf/Subdwarf
• Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB

Cited by in corpus (33)

• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• The Brown Dwarf Kinematics Project (BDKP) I. Proper Motions and Tangential Velocities for a Large Sample of Late-type M, L and T Dwarfs
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• Individual Dynamical Masses of Ultracool Dwarfs
• Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839-0446358
• Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3$\pi$ Survey
• Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime
• Discovery of a Highly Unequal-Mass Binary T Dwarf with Keck Laser Guide Star Adaptive Optics: A Coevality Test of Substellar Theoretical Models and Effective Temperatures
• On the Distribution of Orbital Eccentricities for Very Low-Mass Binaries
• Discovery of the Young L Dwarf WISE J1741102.78-464225.5
• Discovery of a T Dwarf Binary with the Largest Known J-Band Flux Reversal
• A Comprehensive Census of Nearby Infrared Excess Stars
• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph. II. Emergence and Sedimentation of Silicate Clouds in L Dwarfs, and Analysis of the Full M5--T9 Field Dwarf Spectroscopic Sample
• Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1
• The Ultracool SpeXtroscopic Survey. I. Volume-Limited Spectroscopic Sample and Luminosity Function of M7$-$L5 Ultracool Dwarfs
• Young Galaxy Candidates in the Hubble Frontier Fields - III. MACSJ0717.5+3745
• Hubble Space Telescope Observations of Field Ultracool Dwarfs at High Galactic Latitude
• Discovery of a Very Low Mass Triple with Late-M and T Dwarf Components: LP 704-48/SDSS J0006-0852AB
• Trigonometric Parallaxes for Two Late-Type Subdwarfs: LSR1425+71 (sdM8.0) and the Binary LSR1610-00 (sd?M6pec)
• COol Companions ON Ultrawide orbiTS (COCONUTS). I. A High-Gravity T4 Benchmark around an Old White Dwarf and A Re-Examination of the Surface-Gravity Dependence of the L/T Transition
• Discovery of a directly imaged planet to the young solar analog YSES 2
• Hubble Space Telescope Imaging and Spectral Analysis of Two Brown Dwarf Binaries at the L Dwarf/T Dwarf Transition
• WISE2150-7520AB: A very low mass, wide co-moving brown dwarf system discovered through the citizen science project Backyard Worlds: Planet 9
• WISEP J180026.60+013453.1: A Nearby Late L Dwarf Near the Galactic Plane
• Constraints on the binary Properties of mid to late T dwarfs from Hubble Space Telescope WFC3 Observations
• 2MASS J20261584-2943124: An Unresolved L0.5 + T6 Spectral Binary
• On the Correlation between L Dwarf Optical and Infrared Variability and Radio Aurorae
• Disk or Companion: Characterizing Excess Infrared Flux in Seven White Dwarf Systems with Near-Infrared Spectroscopy
• Environment of the submillimeter-bright massive starburst HFLS3 at $z\sim$6.34
• Euclid: The potential of slitless infrared spectroscopy: A z=5.4 quasar and new ultracool dwarfs
• LGS AO Science Impact: Present and Future Perspectives
• The Brown Dwarf Kinematics Project (BDKP). II. Details on Nine Wide Common Proper Motion Very Low-Mass Companions to Nearby Stars
• SpeX Spectroscopy of Unresolved Very Low-Mass Binaries. I. Identification of Seventeen Candidate Binaries Straddling the L Dwarf/T Dwarf Transition