The Young L Dwarf 2MASS J11193254-1137466 is a Planetary-Mass Binary

Abstract

We have discovered that the extremely red, low-gravity L7 dwarf 2MASS J11193254-1137466 is a 0.14" (3.6 AU) binary using Keck laser guide star adaptive optics imaging. 2MASS J11193254-1137466 has previously been identified as a likely member of the TW Hydrae Association (TWA). Using our updated photometric distance and proper motion, a kinematic analysis based on the BANYAN II model gives an 82% probability of TWA membership. At TWA's 10$\pm$3 Myr age and using hot-start evolutionary models, 2MASS J11193254-1137466AB is a pair of $3.7_{-0.9}^{+1.2}$ $M_{\mathrm{Jup}}$ brown dwarfs, making it the lowest-mass binary discovered to date. We estimate an orbital period of $90_{-50}^{+80}$ years. One component is marginally brighter in $K$ band but fainter in $J$ band, making this a probable flux-reversal binary, the first discovered with such a young age. We also imaged the spectrally similar TWA L7 dwarf WISEA J114724.10-204021.3 with Keck and found no sign of binarity. Our evolutionary model-derived $T_{\mathrm{eff}}$ estimate for WISEA J114724.10-204021.3 is $\approx$230 K higher than for 2MASS J11193254-1137466AB, at odds with their spectral similarity. This discrepancy suggests that WISEA J114724.10-204021.3 may actually be a tight binary with masses and temperatures very similar to 2MASS J11193254-1137466AB, or further supporting the idea that near-infrared spectra of young ultracool dwarfs are shaped by factors other than temperature and gravity. 2MASS J11193254-1137466AB will be an essential benchmark for testing evolutionary and atmospheric models in the young planetary-mass regime.

arXiv commentAccepted to ApJ Letters. 8 pages, 3 figures, 2 tables

References in corpus (42)

• The Gaia mission
• The USNO-B Catalog
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• The Pan-STARRS1 Surveys
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood
• The Mauna Kea Observatories Near-Infrared Filter Set. II. Specifications for a New JHKL'M' Filter Set for Infrared Astronomy
• Analysis of isoplanatic high resolution stellar fields by Starfinder code
• Discovery of seven T Tauri stars and a brown dwarf candidate in the nearby TW Hydrae Association
• L and T Dwarf Models and the L to T Transition
• The 0.8-14.5 micron Spectra of Mid-L to Mid-T Dwarfs: Diagnostics of Effective Temperature, Grain Sedimentation, Gas Transport, and Surface Gravity
• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation
• Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b
• A Near-Infrared Spectroscopic Study of Young Field Ultracool Dwarfs
• Bayesian analysis to identify new star candidates in nearby young stellar kinematic groups
• Pan-STARRS Photometric and Astrometric Calibration
• Multiplicity of Nearby Free-floating Ultra-cool Dwarfs: a HST-WFPC2 search for companions
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• BANYAN. II. Very Low Mass and Substellar Candidate Members to Nearby, Young Kinematic Groups With Previously Known Signs of Youth
• Population Properties of Brown Dwarf Analogs to Exoplanets
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets
• Distances, Luminosities, and Temperatures of the Coldest Known Substellar Objects
• The Mauna Kea Observatories Near-Infrared Filter Set. I: Defining Optimal 1-5 $\mu$m Bandpasses
• Hubble Space Telescope Observations of Binary Very-Low-Mass Stars and Brown Dwarfs
• Dynamical Mass of the Substellar Benchmark Binary HD 130948BC
• 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
• HD 203030B: an Unusually Cool Young Sub-Stellar Companion near the L/T Transition
• Keck Laser Guide Star Adaptive Optics Monitoring of 2MASS J1534-2952AB: First Dynamical Mass Determination of a Binary T Dwarf
• On the Distribution of Orbital Eccentricities for Very Low-Mass Binaries
• LACEwING: A New Moving Group Analysis Code
• Two Extraordinary Substellar Binaries at the T/Y Transition and the Y-Band Fluxes of the Coolest Brown Dwarfs
• CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System
• BANYAN. IX. The Initial Mass Function and Planetary-Mass Object Space Density of the TW Hya Association
• WISEA J114724.10-204021.3: A Free-Floating Planetary Mass Member of the TW Hya Association
• A Targeted Search for Peculiarly Red L and T Dwarfs in SDSS, 2MASS, and WISE: Discovery of a Possible L7 Member of the TW Hydrae Association
• The Mass-Luminosity Relation in the L/T Transition: Individual Dynamical Masses for the New J-Band Flux Reversal Binary SDSSJ105213.51+442255.7AB
• Discovery of a Low-Luminosity, Tight Substellar Binary at the T/Y Transition
• The Nearest Isolated Member of the TW Hydrae Association is a Giant Planet Analog
• Brown Dwarf Binaries from Disintegrating Triple Systems

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• A Survey for New Members of Taurus from Stellar to Planetary Masses
• The Hawaii Infrared Parallax Program. IV. A Comprehensive Parallax Survey of L0-T8 dwarfs with UKIRT
• Survivability of planetary systems in young and dense star clusters
• Spitzer Variability Properties of Low-Gravity L Dwarfs
• The Elusive Majority of Young Moving Groups. I. Young Binaries and Lithium-Rich Stars in the Solar Neighborhood
• The Hawaii Infrared Parallax Program. III. 2MASS J0249-0557 c: A Wide Planetary-mass Companion to a Low-mass Binary in the beta Pic Moving Group
• A Census of the TW Hya Association with Gaia
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• 3.8um Imaging of 400-600K Brown Dwarfs and Orbital Constraints for WISEP J045853.90+643452.6AB
• The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass
• A wide planetary-mass companion to a young low-mass brown dwarf in Ophiuchus
• Redder than Red: Discovery of an Exceptionally Red L/T Transition Dwarf
• Spitzer Light Curves of the Young, Planetary-Mass TW Hya Members 2MASS J11193254-1137466AB and WISEA J114724.10-204021.3
• A Census of the 32 Ori Association with Gaia
• A Near-infrared Variability Survey of Young Planetary-mass Objects
• New Candidates for Planetary-mass Brown Dwarfs in IC 348
• OGLE-2016-BLG-1266: A Probable Brown-Dwarf/Planet Binary at the Deuterium Fusion Limit
• Dynamics of Binary Planets within Star Clusters
• Spectral characterization of young LT dwarfs
• Spectral characterization of newly detected young substellar binaries with SINFONI
• Formation of free-floating planetary mass objects via circumstellar disk encounters
• X-SHYNE: X-Shooter spectra of young exoplanet analogs II. Presentation and analysis of the full library
• An L+T Spectral Binary with Possible AB Doradus Kinematics
• Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
• One of Everything: The Breakthrough Listen Exotica Catalog
• History of Globulettes in the Milky Way
• A review on substellar objects beyond the deuterium burning mass limit: planets, brown dwarfs or what?
• The Brown Dwarf Kinematics Project (BDKP). V. Radial and Rotational Velocities of T Dwarfs from Keck/NIRSPEC High-Resolution Spectroscopy
• Special cases : moons, rings, comets, trojans