Clouds, Gravity and Metallicity in Blue L dwarfs: The Case of 2MASS J11263991-5003550

Abstract

Optical and near-infrared spectroscopy of the newly discovered peculiar L dwarf 2MASS J11263991-5003550 are presented. Folkes et al. identified this source as a high proper motion L9+/-1 dwarf based on its strong H2O absorption at 1.4 micron. We find that the optical spectrum of 2MASS J1126-5003 is in fact consistent with that of a normal L4.5 dwarf with notably enhanced FeH absorption at 9896 A. However, its near-infrared spectrum is unusually blue, with strong H2O and weak CO bands similar in character to several recently identified ``blue L dwarfs''. Using 2MASS J1126-5003 as a case study, and guided by trends in the condensate cloud models of Burrows et al. and Marley et al., we find that the observed spectral peculiarities of these sources can be adequately explained by the presence of thin and/or large-grained condensate clouds as compared to normal field L dwarfs. Atypical surface gravities or metallicities alone cannot reproduce the observed peculiarities, although they may be partly responsible for the unusual condensate properties. We also rule out unresolved multiplicity as a cause for the spectral peculiarities of 2MASS J1126-5003. Our analysis is supported by examination of Spitzer mid-infrared spectral data from Cushing et al. which show that bluer L dwarfs tend to have weaker 10 micron absorption, a feature tentatively associated with silicate oxide grains. With their unique spectral properties, blue L dwarfs like 2MASS J1126-5003 should prove useful in studying the formation and properties of condensates and condensate clouds in low temperature atmospheres.

25 pages, 12 figures, accepted to ApJ

References in corpus (11)

• Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field
• Characterizing Young Brown Dwarfs using Low Resolution Near-IR Spectra
• Activity and Kinematics of Ultracool Dwarfs Including An Amazing Flare Observation
• Discovery of 11 New T Dwarfs in the Two Micron All-Sky Survey, Including a Possible L/T Transition Binary
• Physical parameters of two very cool T dwarfs
• Optical Spectroscopy of 2MASS Color-Selected Ultracool Subdwarfs
• 3.6-7.9 um Photometry of L and T Dwarfs and the Prevalence of Vertical Mixing in their Atmospheres
• Discovery of a High Proper Motion L Dwarf Binary: 2MASS J15200224-4422419AB
• SDSS J080531.84+481233.0: An Unresolved L Dwarf/T Dwarf Binary
• Discovery of a nearby L-T transition object in the Southern Galactic plane
• Halo Stars Near the Hydrogen-Burning Limit: The M/L Subdwarf Transition

Cited by in corpus (44)

• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• 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
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf "Lithium Test" at Early Ages
• Transmission spectral properties of clouds for hot Jupiter exoplanets
• A comparison of chemistry and dust cloud formation in ultracool dwarf model atmospheres
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839-0446358
• The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs
• Discovery of Two Nearby, Peculiar L Dwarfs from the 2MASS Proper Motion Survey: Young or Metal-Rich?
• SpeX Spectroscopy of Unresolved Very Low Mass Binaries. II. Identification of Fourteen Candidate Binaries with Late-M/Early-L and T Dwarf Components
• BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
• A Volume-Limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
• Doppler Imaging of Exoplanets and Brown Dwarfs
• 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
• Discovery of an M9.5 Candidate Brown Dwarf in the TW Hydrae Association - DENIS J124514.1-442907
• The Brown dwarf Atmosphere Monitoring (BAM) Project I: The largest near-IR monitoring survey of L- & T-dwarfs
• An independent analysis of the brown dwarf atmosphere monitoring (BAM) data: large-amplitude variability is rare outside the L/T transition
• Primeval very low-mass stars and brown dwarfs. I. Six new L subdwarfs, classification and atmospheric properties
• The Hawaii Infrared Parallax Program. IV. A Comprehensive Parallax Survey of L0-T8 dwarfs with UKIRT
• An Infrared High Proper Motion Survey Using 2MASS and SDSS: Discovery of M, L and T Dwarfs
• Discovery of a Wide Substellar Companion to a Nearby Low-Mass Star
• Characterization of High Proper Motion Objects from the Wide-field Infrared Survey Explorer
• SIMP J2154-1055: A New Low-Gravity L4$\beta$ Brown Dwarf Candidate Member of the Argus Association
• Quartz Clouds in the Dayside Atmosphere of the Quintessential Hot Jupiter HD 189733 b
• A Search for Photometric Variability in L and T type Brown Dwarf Atmospheres
• A Brown Dwarf Census from the SIMP Survey
• A Search for FeH in Hot-Jupiter Atmospheres with High-Dispersion Spectroscopy
• Uniform Forward-Modeling Analysis of Ultracool Dwarfs. II. Atmospheric Properties of 55 Late-T Dwarfs
• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph -- III. Dust Grains in Young L Dwarf Atmospheres Are Heavier
• $K2$ Ultracool Dwarfs Survey. VI. White light superflares observed on an L5 dwarf and flare rates of L dwarfs
• The ages of L dwarfs
• Cloud Atlas: High-precision HST/WFC3/IR Time-Resolved Observations of Directly-Imaged Exoplanet HD106906b
• Redder than Red: Discovery of an Exceptionally Red L/T Transition Dwarf
• Optical Spectra of Ultracool Dwarfs with the Southern African Large Telescope
• The First Mid-Infrared Spectra of Cool White Dwarfs
• The $\text{Gaia}$ Ultra-Cool Dwarf Sample $-$ III: Seven new multiple systems containing at least one $\text{Gaia}$ DR2 ultra-cool dwarf
• Spectral Variability of Two Rapidly Rotating Brown Dwarfs: 2MASS J08354256-0819237 and 2MASS J18212815+1414010
• The Influence of Dust Formation Modelling on Na I and K I Line Profiles in Substellar Atmospheres
• Weather on Other Worlds. VI. Optical Spectrophotometry of Luhman 16B Reveals Large-amplitude Variations in the Alkali Lines
• J-PLUS: Discovery and characterisation of ultracool dwarfs using Virtual Observatory tools
• Detection of Na in the atmosphere of the hot Jupiter HAT-P-55b
• Silicate Clouds, SiO, and Molecular Trends across the L-T Sequence: A JWST/MIRI LRS Spectral Library of Brown Dwarfs
• Using Old and New Approaches: Determining Physical Properties of Brown Dwarfs with Empirical Relations and Machine Learning Models