An Atmospheric Retrieval of the Brown Dwarf Gliese 229B
arXiv:2210.13614 · doi:10.3847/1538-4357/ac9cc9
Abstract
We present results from an atmospheric retrieval analysis of Gl 229B using the BREWSTER retrieval code. We find the best fit model to be cloud-free, consistent with the T dwarf retrieval work of Line et al. 2017, Zalesky et al. 2022 and Gonzales et al. 2020. Fundamental parameters (mass, radius, log(L_{Bol}/L_{Sun}), log(g)) determined from our model agree within 1σto SED-derived values except for T_{eff} where our retrieved T_{eff} is approximately 100 K cooler than the evolutionary model-based SED value. We find a retrieved mass of 50^{+12}_{-9} M_{Jup}, however, we also find that the observables of Gl 229B can be explained by a cloud-free model with a prior on mass at the dynamical value, 70 M_{Jup}. We are able to constrain abundances for H_2O, CO, CH_4, NH_3, Na and K and find a supersolar C/O ratio as compared to its primary, Gl 229A. We report an overall subsolar metallicity due to atmospheric oxygen depletion but find a solar [C/H], which matches that of the primary. We find that this work contributes to a growing trend in retrieval-based studies, particularly for brown dwarfs, toward supersolar C/O ratios and discuss the implications of this result on formation mechanisms, internal physical processes as well as model biases.
26 pages, 8 tables, 8 figures. Accepted for publication in ApJ
References in corpus (27)
- The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
- Constraining the Age-Activity Relation for Cool Stars: The SDSS DR5 Low-Mass Star Spectroscopic Sample
- Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
- Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
- A statistical test for Nested Sampling algorithms
- Transmission spectral properties of clouds for hot Jupiter exoplanets
- Methane, Carbon Monoxide, and Ammonia in Brown Dwarfs and Self-Luminous Giant Planets
- Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
- Planets Around Low-Mass Stars (PALMS). IV. The Outer Architecture of M Dwarf Planetary Systems
- Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs I: Characterizing Benchmarks, Gl570D and HD3651B
- K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba
- The discovery of an M4+T8.5 binary system
- M Dwarf Metallicities and Giant Planet Occurrence: Ironing Out Uncertainties and Systematics
- Optical Spectroscopy of 2MASS Color-Selected Ultracool Subdwarfs
- Metallicity of M dwarfs IV. A high-precision [Fe/H] and Teff technique from high-resolution optical spectra for M dwarfs
- Helios-r2 -- A new Bayesian, open-source retrieval model for brown dwarfs and exoplanet atmospheres
- Atmospheres of Brown Dwarfs
- A Uniform Retrieval Analysis of Ultracool Dwarfs. III. Properties of Y-Dwarfs
- Planet formation around M dwarfs via disc instability: Fragmentation conditions and protoplanet properties
- Retrieving the C and O Abundances of HR 7672~AB: a Solar-Type Primary Star with a Benchmark Brown Dwarf
- On the Chemical Abundance of HR 8799 and the Planet c
- An Information-Theoretic Approach to Optimize JWST Observations and Retrievals of Transiting Exoplanet Atmospheres
- WISE2150-7520AB: A very low mass, wide co-moving brown dwarf system discovered through the citizen science project Backyard Worlds: Planet 9
- Near Infrared Spectroscopy of M Dwarfs. I. CO Molecule as an Abundance Indicator of Carbon
- Precise Dynamical Masses of Epsilon Indi Ba and Bb: Evidence of Slowed Cooling at the L/T Transition
- A Wide Planetary Mass Companion Discovered Through the Citizen Science Project Backyard Worlds: Planet 9
- Near Infrared Spectroscopy of M Dwarfs. II. H2O Molecule as an Abundance Indicator of Oxygen