The Spectrum of the Brown Dwarf Gliese 229B

Abstract

We present a spectrum of the cool (T_eff = 900 K) brown dwarf Gliese 229B. This spectrum, with a relatively high signal-to-noise ratio per spectral resolution element (> 30), spans the wavelength range from 0.837 microns to 5.0 microns. We identify a total of four different major methane absorption features, including the fundamental band at 3.3 microns, at least four steam bands, and two neutral cesium features. We confirm the recent detection of carbon monoxide (CO) in excess of what is predicted by thermochemical equilibrium calculations. Carbon is primarily involved in a chemical balance between methane and CO at the temperatures and pressures present in the outer parts of a brown dwarf. At lower temperatures, the balance favors methane, while in the deeper, hotter regions, the reaction reverses to convert methane into CO. The presence of CO in the observable part of the atmosphere is therefore a sensitive indicator of vertical flows. The high signal-to-noise ratio in the 1 to 2.5 microns region permits us to place constraints on the quantity of dust in the atmosphere of the brown dwarf. We are unable to reconcile the observed spectrum with synthetic spectra that include the presences of dust. The presence of CO but lack of dust may be a clue to the location of the boundaries of the outer convective region of the atmosphere: The lack of dust may mean that it is not being conveyed into the photosphere by convection, or that it exists in patchy clouds. If the dust is not in clouds, but rather sits below the outer convective region, we estimate that the boundary between outer convective and inner radiative layers is between 1250 K and 1600 K, in agreement with recent models.

15 pages, 8 figures

References in corpus (3)

• A Non-Gray Theory of Extrasolar Giant Planets and Brown Dwarfs
• Spectral evidence for dust in late-type M dwarfs
• The FeH Wing-Ford Band in Spectra of M Stars

Cited by in corpus (92)

• Detection of an Extrasolar Planet Atmosphere
• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• The Theory of Brown Dwarfs and Extrasolar Giant Planets
• An Infrared Spectroscopic Sequence of M, L and T Dwarfs
• Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
• Theory of Low-Mass Stars and Substellar Objects
• Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres
• A Unified Near Infrared Spectral Classification Scheme for T Dwarfs
• L' and M' Photometry of Ultracool Dwarfs
• Towards Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis
• Exoplanet Atmospheres
• The Spectra of T Dwarfs I: Near-Infrared Data and Spectral Classification
• The NIRSPEC Brown Dwarf Spectroscopic Survey. I. Low-Resolution Near-Infrared Spectra
• Infrared Photometry of Late-M, L, and T Dwarfs
• Masses, Radii, and Cloud Properties of the HR 8799 Planets
• Evidence for Cloud Disruption in the L/T Dwarf Transition
• The Near-Infrared and Optical Spectra of Methane Dwarfs and Brown Dwarfs
• Dynamics and Disequilibrium Carbon Chemistry in Hot Jupiter Atmospheres, With Application to HD 209458b
• Spitzer Infrared Spectrograph Observations of M, L, and T Dwarfs
• On the Cool Side: Modeling the Atmospheres of Brown Dwarfs and Giant Planets
• The Discovery of a Field Methane Dwarf from Sloan Digital Sky Survey Commissioning Data
• Binaries and the L Dwarf/T Dwarf Transition
• Four nearby L dwarfs
• Quenching of Carbon Monoxide and Methane in the Atmospheres of Cool Brown Dwarfs and Hot Jupiters
• The Spectra of T Dwarfs. II. Red Optical Data
• Molecular Abundances in the Atmosphere of the T Dwarf Gl 229B
• Dust in the Photospheric Environment: Unified Cloudy Models of M, L, and T Dwarfs
• Ab initio equations of state for hydrogen (H-REOS.3) and helium (He-REOS.3) and their implications for the interior of Brown Dwarfs
• Discovery of a Low-Mass Brown Dwarf Companion of the Young Nearby Star G196-3
• Dust in brown dwarfs and extra-solar planets II. Cloud formation for cosmologically evolving abundances
• PICASO 3.0: A One-Dimensional Climate Model for Giant Planets and Brown Dwarfs
• Physical parameters of two very cool T dwarfs
• The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data
• Discovery of a Bright Field Methane (T-type) Brown Dwarf by 2MASS
• High-Contrast Observations in Optical and Infrared Astronomy
• Searching for Weather in Brown Dwarfs
• Astrometry and Photometry with Coronagraphs
• The Sonora Substellar Atmosphere Models. IV. Elf Owl: Atmospheric Mixing and Chemical Disequilibrium with Varying Metallicity and C/O Ratios
• 3.6-7.9 um Photometry of L and T Dwarfs and the Prevalence of Vertical Mixing in their Atmospheres
• Coronagraphic Survey for Companions of Stars within 8 pc
• Observations of Disequilibrium CO Chemistry in the Coldest Brown Dwarfs
• The Onset of Methane in L Dwarfs
• The AllWISE Motion Survey, Part 2
• The Las Campanas Infrared Survey. IV. The Photometric Redshift Survey and the Rest-frame R-band Galaxy Luminosity Function at 0.5 <= z <= 1.5
• AKARI Observations of Brown Dwarfs. III. CO, CO2 and CH4 Fundamental Bands and Physical Parameters
• Detection of H Alpha Emission in a Methane (T-Type) Brown Dwarf
• Revised Fluxes for Gliese 229B
• AKARI Observations of Brown Dwarfs I.: CO and CO_2 Bands in the Near-Infrared Spectra
• Spectroscopic Detection of Carbon Monoxide in Two Late-type T Dwarfs
• Probing the Extent of Vertical Mixing in Brown Dwarf Atmospheres with Disequilibrium Chemistry
• The Gaia Ultracool Dwarf Sample. I. Known L and T dwarfs and the first Gaia data release
• A Dynamical Mass of $70\pm 5$ Jupiter Masses for Gliese 229B, the First T Dwarf
• An Improved Red Spectrum of the Methane or T-dwarf SDSS 1624+0029: Role of the Alkali Metals
• Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars
• Atmospheric Analysis of the M/L- and M/T-Dwarf Binary Systems LHS 102 and Gliese 229
• Spectral Classification and Effective Temperatures of L and T Dwarfs Based of Near-Infrared Spectra
• The Las Campanas Infrared Survey. III. The H-band Imaging Survey and the Near-Infrared and Optical Photometric Catalogs
• The First JWST Spectral Energy Distribution of a Y dwarf
• The Coldest Brown Dwarf (Or Free Floating Planet)?: The Y Dwarf WISE 1828+2650
• FIRE Spectroscopy of Five Late-type T Dwarfs Discovered with the Wide-field Infrared Survey Explorer
• SDSS J141624.08+134826.7: Blue L Dwarfs and Non-Equilibrium Chemistry
• Akari Observations of Brown Dwarfs. II CO2 as Probe of Carbon and Oxygen Abundances in Brown Dwarfs
• A Candidate Protoplanet in the Taurus Star Forming Region
• On the Nature of the Unique H$\alpha$-Emitting T Dwarf 2MASS J12373919+6526148
• Emission lines in the atmosphere of the irradiated brown dwarf WD0137-349B
• The Visual Orbit of 64 Piscum
• Thermal Infrared Constraint to a Planetary Companion of Vega with the MMT Adaptive Optics System
• A 1.46-2.48 $\mu$m Spectroscopic Atlas of a T6 Dwarf (1060 K) Atmosphere with IGRINS: First Detections of H${}_2$S and H${}_2$, and Verification of H${}_2$O, CH${}_4$, and NH${}_3$ Line Lists
• An Atmospheric Retrieval of the Brown Dwarf Gliese 229B
• Information content of JWST-NIRSPEC transmission spectra of warm Neptunes
• CORMASS: A Compact and Efficient NIR Spectrograph for Studying Low-Mass Objects
• Convective dynamics and disequilibrium chemistry in the atmospheres of giant planets and brown dwarfs
• Methane band and Spitzer mid-IR imaging of L and T dwarf candidates in the Pleiades
• Dynamically coupled kinetic chemistry in brown dwarf atmospheres I. Performing global scale kinetic modelling
• Near-infrared photometry of WISE J085510.74$-$071442.5
• Physical Properties of Gliese 229B Based on Newly Determined Carbon and Oxygen Abundances of Gliese 229A
• A search for lithium in metal-poor L dwarfs
• GJ 229B: Solving the Puzzle of the First Known T-Dwarf with the APOLLO Retrieval Code
• The Future of Ultracool Dwarf Science with JWST
• A k-NN Method to Classify Rare Astronomical Sources: Photometric Search of Brown Dwarfs with Spitzer/IRAC
• Discovery of the Binarity of Gliese 229B, and Constraints on the System's Properties
• The infrared colors of 51 Eridani b: micrometereoid dust or chemical disequilibrium?
• A Unified Spectroscopic and Photometric Model to Infer Surface Inhomogeneity: Application to Luhman 16B
• Atmospheric abundances and bulk properties of the binary brown dwarf Gliese 229 Bab from JWST/MIRI spectroscopy
• Investigating Possible Binarity for GJ 229B
• The ExoGRAVITY survey: A K-band spectral library of giant exoplanet and brown dwarf companions
• The Classification of T Dwarfs
• Companions of Stars: From Other Stars to Brown Dwarfs to Planets: The Discovery of the First Methane Brown Dwarf
• Infrared observations of a mid-L dwarf with strong H$\alpha$ emission
• Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B
• Spectral Classification; Old and Contemporary
• A Uniform Retrieval Analysis of Ultra-cool Dwarfs. IV. A Statistical Census from 50 Late-T Dwarfs