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

Abstract

We present new 5.2-14.5 micron low-resolution spectra of 14 mid-L to mid-T dwarfs, as well as 3.0-4.1 micron spectra for five of these dwarfs. These data are supplemented by existing red and near-infrared spectra (0.6-2.5 micron), as well as red through mid-infrared spectroscopy of seven other L and T dwarfs presented by Cushing et al. (2008). We compare these spectra to those generated from the model atmospheres of Saumon & Marley (2008). The models reproduce the observed spectra well, except in the case of one very red L3.5 dwarf, 2MASS J22244381-0158521. The broad wavelength coverage allows us to constrain almost independently the four parameters used to describe these photospheres in our models: effective temperature (Teff), surface gravity, grain sedimentation efficiency (fsed) and vertical gas transport efficiency (Kzz). The sample of L3.5 to T5.5 dwarfs spans the range 1800 < Teff < 1000 K, with an L-T transition (spectral types L7-T4) that lies between 1400 K and 1100K for dwarfs with typical near-infrared colors; bluer and redder dwarfs can be 100 K warmer or cooler, respectively, when using infrared spectral types. In this model analysis, fsed increases rapidly between types T0 and T4, indicating that increased sedimentation can explain the rapid disappearance of clouds at this stage of brown dwarf evolution. There is a suggestion that the transition to dust-free atmospheres happens at lower temperatures for lower gravity dwarfs.

53 pages, 16 figures, to be published in the Astrophysical Journal

References in corpus (24)

• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres
• Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs
• Discovery of Two T Dwarf Companions with the Spitzer Space Telescope
• A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf "Lithium Test" at Early Ages
• A comparison of chemistry and dust cloud formation in ultracool dwarf model atmospheres
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
• Spitzer/IRAC Photometry of M, L, and T Dwarfs
• Dust in Brown Dwarfs and Extra-solar Planets I. Chemical composition and spectral appearance of quasi-static cloud layers
• A Systematic Study of Departures from Chemical Equilibrium in the Atmospheres of Substellar Mass Objects
• A search for binary systems among the nearest L dwarfs
• HD 203030B: an Unusually Cool Young Sub-Stellar Companion near the L/T Transition
• Clouds, Gravity and Metallicity in Blue L dwarfs: The Case of 2MASS J11263991-5003550
• A very cool brown dwarf in UKIDSS DR1
• K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba
• Physical parameters of two very cool T dwarfs
• HD3651B: the first directly imaged brown dwarf companion of an exoplanet host star
• Discovery of a T Dwarf Binary with the Largest Known J-Band Flux Reversal
• 3.6-7.9 um Photometry of L and T Dwarfs and the Prevalence of Vertical Mixing in their Atmospheres
• The Physical Properties of HD 3651B: An Extrasolar Nemesis?
• Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition
• SDSS J080531.84+481233.0: An Unresolved L Dwarf/T Dwarf Binary
• Proper motions of field L and T dwarfs

Cited by in corpus (108)

• Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
• A new set of atmosphere and evolution models for cool T-Y brown dwarfs and giant exoplanets
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• Aerosol Composition of Hot Giant Exoplanets Dominated by Silicates and Hydrocarbon Hazes
• An accurate, extensive, and practical line list of methane for the HITEMP database
• Gaia Data Release 3: Astrophysical parameters inference system (Apsis) I -- methods and content overview
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• Water Clouds in Y Dwarfs and Exoplanets
• Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs I: Characterizing Benchmarks, Gl570D and HD3651B
• Gaia Data Release 3: Apsis II -- Stellar Parameters
• Vertical Atmospheric Structure in a Variable Brown Dwarf: Pressure-dependent Phase Shifts in Simultaneous Hubble Space Telescope-Spitzer Light Curves
• Discovery of a wide planetary-mass companion to the young M3 star GU Psc
• Characterizing 51 Eri b from 1-5 $\mu$m: a partly-cloudy exoplanet
• PICASO 3.0: A One-Dimensional Climate Model for Giant Planets and Brown Dwarfs
• Beyond Equilibrium Temperature: How the Atmosphere/Interior Connection Affects the Onset of Methane, Ammonia, and Clouds in Warm Transiting Giant Planets
• Atmospheric Dynamics of Hot Giant Planets and Brown Dwarfs
• The spectrum of hot methane in astronomical objects using a comprehensive computed line list
• Aerosols in Exoplanet Atmospheres
• BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
• WASP-80b has a dayside within the T-dwarf range
• A Volume-Limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
• Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158
• Gemini Planet Imager Spectroscopy of the HR 8799 planets c and d
• Atmospheric Regimes and Trends on Exoplanets and Brown Dwarfs
• Doppler Imaging of Exoplanets and Brown Dwarfs
• A Search for L/T Transition Dwarfs With Pan-STARRS1 and WISE. II. L/T Transition Atmospheres and Young Discoveries
• A large spectroscopic sample of L and T dwarfs from UKIDSS LAS: peculiar objects, binaries, and space density
• Keck/NIRC2 $L$'-Band Imaging of Jovian-Mass Accreting Protoplanets around PDS 70
• Near-infrared photometry of Y dwarfs: low ammonia abundance and the onset of water clouds
• 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
• Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: effects of rotation
• Temperature Fluctuations as a Source of Brown Dwarf Variability
• Direct Imaging and Astrometric Detection of a Gas Giant Planet Orbiting an Accelerating Star
• Cloud structure of the nearest brown dwarfs: Spectroscopic variability of Luhman 16AB from the Hubble Space Telescope
• WISEP J004701.06+680352.1: An intermediate surface gravity, dusty brown dwarf in the AB Dor Moving Group
• Magellan Adaptive Optics first-light observations of the exoplanet $\beta$ Pic b. I. Direct imaging in the far-red optical with MagAO+VisAO and in the near-IR with NICI
• Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf
• Direct Imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS
• Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-Cool Dwarfs
• HST Rotational Spectral Mapping of Two L-Type Brown Dwarfs: Variability In and Out of Water Bands Indicates High-Altitude Haze Layers
• New Evidence for a Substellar Luminosity Problem: Dynamical Mass for the Brown Dwarf Binary Gl 417BC
• Signatures of Cloud, Temperature, and Gravity From Spectra of the Closest Brown Dwarfs
• Trigonometric parallaxes of young field L dwarfs
• The Young L Dwarf 2MASS J11193254-1137466 is a Planetary-Mass Binary
• The substellar companion in the eclipsing white dwarf binary SDSS J141126.20+200911.1
• SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
• A search for a 5th planet around HR 8799 using the star-hopping RDI technique at VLT/SPHERE
• Near-Infrared Detection and Characterization of the Exoplanet HD 95086 b with the Gemini Planet Imager
• Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY
• WISE J072003.20-084651.2: An Old and Active M9.5 + T5 Spectral Binary 6 pc from the Sun
• Empirically Determining Substellar Cloud Compositions in the era of JWST
• The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs
• A First-Look Atmospheric Modeling Study of the Young Directly-Imaged Planet-Mass Companion, ROXs 42Bb
• Infrared Excesses around Bright White Dwarfs from Gaia and unWISE I
• A New Sedimentation Model for Greater Cloud Diversity in Giant Exoplanets and Brown Dwarfs
• The Hawaii Infrared Parallax Program. V. New T-Dwarf Members and Candidate Members of Nearby Young Moving Groups
• 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
• An Approach for Retrieving Temperatures and Abundances in Brown Dwarf Atmospheres
• The Mass-Luminosity Relation in the L/T Transition: Individual Dynamical Masses for the New J-Band Flux Reversal Binary SDSSJ105213.51+442255.7AB
• Gaia Data Release 3: A Golden Sample of Astrophysical Parameters
• Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets
• Uniform Forward-Modeling Analysis of Ultracool Dwarfs. II. Atmospheric Properties of 55 Late-T Dwarfs
• Photometric Monitoring of the Coldest Known Brown Dwarf with the Spitzer Space Telescope
• A reduced chemical scheme for modelling warm to hot hydrogen-dominated atmospheres
• Uniform Forward-Modeling Analysis of Ultracool Dwarfs. I. Methodology and Benchmarking
• BANYAN. VIII. New Low-Mass Stars and Brown Dwarfs with Candidate Circumstellar Disks
• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph -- III. Dust Grains in Young L Dwarf Atmospheres Are Heavier
• The VAST Survey - IV. A wide brown dwarf companion to the A3V star $\zeta$ Delphini
• An image-plane algorithm for JWST's non-redundant aperture mask data
• Supervised Machine Learning for Intercomparison of Model Grids of Brown Dwarfs: Application to GJ 570D and the Epsilon Indi B Binary System
• Jet Streams and Tracer Mixing in the Atmospheres of Brown Dwarfs and Isolated Young Giant Planets
• GRAVITY K-band spectroscopy of HD 206893 B: brown dwarf or exoplanet
• Rotation periods and photometric variability of rapidly rotating ultra-cool dwarfs
• Detection of a giant white-light flare on an L2.5 dwarf with the Next Generation Transit Survey
• The Late-Type Extension to MoVeRS (LaTE-MoVeRS): Proper motion verified low-mass stars and brown dwarfs from SDSS, 2MASS, and WISE
• An Improved Near-Infrared Spectrum of the Archetype Y Dwarf WISEP J182831.08+265037.8
• Spectral library of age-benchmark low-mass stars and brown dwarfs
• Calibrating Ultracool Dwarfs: Optical Template Spectra, Bolometric Corrections, and $\chi$ Values
• Cloud Atlas: High-precision HST/WFC3/IR Time-Resolved Observations of Directly-Imaged Exoplanet HD106906b
• The Prototypical Young L/T-Transition Dwarf HD 203030B Likely Has Planetary Mass
• Ultracool dwarfs in Gaia DR3
• Microphysics of Water Clouds in the Atmospheres of Y Dwarfs and Temperate Giant Planets
• A Near-infrared Variability Survey of Young Planetary-mass Objects
• The continued optical to mid-IR evolution of V838 Monocerotis
• Dynamically coupled kinetic chemistry in brown dwarf atmospheres I. Performing global scale kinetic modelling
• VLTI/GRAVITY Observations and Characterization of the Brown Dwarf Companion HD 72946 B
• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph. I. An Accurate Look at the L-to-T Transition at $\sim$300 Myr from Optical through Mid-infrared Spectrophotometry
• Astrometric orbits of spectral binary brown dwarfs I: Massive T dwarf companions to 2M1059$-$21 and 2M0805$+$48
• In-depth direct imaging and spectroscopic characterization of the young Solar System analog HD 95086
• The Effect of Atmospheric Cooling on the Vertical Velocity Dispersion and Density Distribution of Brown Dwarfs
• Reflected Light Phase Curves in the TESS Era
• The $\text{Gaia}$ Ultra-Cool Dwarf Sample $-$ III: Seven new multiple systems containing at least one $\text{Gaia}$ DR2 ultra-cool dwarf
• High Contrast Thermal Infrared Spectroscopy with ALES: The 3-4$\mu$m Spectrum of $\kappa$ Andromedae b
• Optical Transmission Spectra of Hot-Jupiters: Effects of Scattering
• L-band Spectroscopy with Magellan-AO/Clio2: First Results on Young Low-Mass Companions
• Discovery of the Exceptionally Short Period Ultracool Dwarf Binary LP 413-53AB
• Hotter Than Expected: HST/WFC3 Phase-resolved Spectroscopy of a Rare Irradiated Brown Dwarf with Strong Internal Heat Flux
• Science Commissioning of NIHTS: The Near-infrared High Throughput Spectrograph on the Lowell Discovery Telescope
• X-SHYNE: X-Shooter spectra of young exoplanet analogs II. Presentation and analysis of the full library
• High Spatial Resolution Thermal-Infrared Spectroscopy with ALES: Resolved Spectra of the Benchmark Brown Dwarf Binary HD 130948BC
• The $\text{MSG}$ model for cloudy substellar atmospheres: A grid of self-consistent substellar atmosphere models with microphysical cloud formation
• $L$-band Spectra of Young Brown Dwarfs
• Near-infrared spectroscopic characterisation of Gaia ultra-cool dwarf candidates; Spectral types and peculiarities
• The Sonora Brown Dwarf Atmosphere and Evolution Models I. Model Description and Application to Cloudless Atmospheres in Rainout Chemical Equilibrium
• Spectral analysis of two directly imaged benchmark L dwarf companions at the stellar-substellar boundary
• The Brown Dwarf Kinematics Project (BDKP). V. Radial and Rotational Velocities of T Dwarfs from Keck/NIRSPEC High-Resolution Spectroscopy
• The Gaia Ultracool Dwarf Sample -- IV. GTC/OSIRIS optical spectra of Gaia late-M and L dwarfs
• L-band Integral Field Spectroscopy of the HR 8799 Planetary System