Methane Emission From a Cool Brown Dwarf

Abstract

Beyond our solar system, aurorae have been inferred from radio observations of isolated brown dwarfs (e.g. Hallinan et al. 2006; Kao et al. 2023). Within our solar system, giant planets have auroral emission with signatures across the electromagnetic spectrum including infrared emission of H3+ and methane. Isolated brown dwarfs with auroral signatures in the radio have been searched for corresponding infrared features but have only had null detections (e.g. Gibbs et al. 2022). CWISEP J193518.59-154620.3. (W1935 for short) is an isolated brown dwarf with a temperature of ~482 K. Here we report JWST observations of strong methane emission from W1935 at 3.326 microns. Atmospheric modeling leads us to conclude that a temperature inversion of ~300 K centered at 1-10 millibar replicates the feature. This represents an atmospheric temperature inversion for a Jupiter-like atmosphere without irradiation from a host star. A plausible explanation for the strong inversion is heating by auroral processes, although other internal and/or external dynamical processes cannot be ruled out. The best fit model rules out the contribution of H3+ emission which is prominent in solar system gas giants however this is consistent with rapid destruction of H3+ at the higher pressure where the W1935 emission originates (e.g. Helling et al. 2019).

Accepted in Nature 9 February 2024

References in corpus (47)

• emcee: The MCMC Hammer
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The slope of the black-hole mass versus velocity dispersion correlation
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• The Discovery of Y Dwarfs Using Data from the Wide-field Infrared Survey Explorer (WISE)
• Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres over a Range of Metallicities and Temperatures
• Further Defining Spectral Type "Y" and Exploring the Low-mass End of the Field Brown Dwarf Mass Function
• Fundamental Parameters and Spectral Energy Distributions of Young and Field Age Objects with Masses Spanning the Stellar to Planetary Regime
• Data analysis recipes: Using Markov Chain Monte Carlo
• The CatWISE2020 Catalog
• The Brown Dwarf Kinematics Project (BDKP) I. Proper Motions and Tangential Velocities for a Large Sample of Late-type M, L and T Dwarfs
• An accurate, extensive, and practical line list of methane for the HITEMP database
• Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun
• Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs I: Characterizing Benchmarks, Gl570D and HD3651B
• The Field Substellar Mass Function Based on the Full-sky 20-pc Census of 525 L, T, and Y Dwarfs
• Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM 513-46546: Broadband Coherent Emission at the Substellar Boundary?
• Retrieval of atmospheric properties of cloudy L dwarfs
• New H2 collision-induced absorption and NH3 opacity and the spectra of the coolest brown dwarfs
• Preliminary Trigonometric Parallaxes of 184 Late-T and Y Dwarfs and an Analysis of the Field Substellar Mass Function into the "Planetary" Mass Regime
• The CatWISE Preliminary Catalog: Motions from $WISE$ and $NEOWISE$ Data
• Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs II: Properties of 11 T-dwarfs
• Hubble Space Telescope Spectroscopy of Brown Dwarfs Discovered with the Wide-field Infrared Survey Explorer
• The Strongest Magnetic Fields on the Coolest Brown Dwarfs
• Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158
• WISE Y Dwarfs As Probes of the Brown Dwarf-Exoplanet Connection
• Observations of Disequilibrium CO Chemistry in the Coldest Brown Dwarfs
• Let the Great World Spin: Revealing the Stormy, Turbulent Nature of Young Giant Exoplanet Analogs with the Spitzer Space Telescope
• The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project
• The Luminosities of the Coldest Brown Dwarfs
• EXOPLINES: Molecular Absorption Cross-Section Database for Brown Dwarf and Giant Exoplanet Atmospheres
• Signatures of Cloud, Temperature, and Gravity From Spectra of the Closest Brown Dwarfs
• The First Spectrum of the Coldest Brown Dwarf
• The First JWST Spectral Energy Distribution of a Y dwarf
• Expanding the Y Dwarf Census with Spitzer Follow-up of the Coldest CatWISE Solar Neighborhood Discoveries
• Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry
• Retrieval of SDSS J1416+1348AB
• Y dwarf Trigonometric Parallaxes from the Spitzer Space Telescope
• Resolved imaging of an extrasolar radiation belt around an ultracool dwarf
• Retrieval study of cool, directly imaged exoplanet 51 Eri b
• An Atmospheric Retrieval of the Brown Dwarf Gliese 229B
• Near-Infrared Spectroscopy of the Y0 WISEP J173835.52+273258.9 and the Y1 WISE J035000.32-565830.2: the Importance of Non-Equilibrium Chemistry
• CWISEP J193518.59$-$154620.3: An Extremely Cold Brown Dwarf in the Solar Neighborhood Discovered with CatWISE
• Atmosphere Models of Brown Dwarfs Irradiated by White Dwarfs: Analogues for Hot and Ultra-Hot Jupiters
• Limits on the Auroral Generation of H${}_3^{+}$ in Brown Dwarf and Extrasolar Giant Planet Atmospheres with Keck/NIRSPEC
• Understanding Fundamental Properties and Atmospheric Features of Subdwarfs via a Case Study of SDSS J125637.13-022452.4
• The puzzle of the formation of T8 dwarf Ross 458c

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• The JWST Weather Report: retrieving temperature variations, auroral heating, and static cloud coverage on SIMP-0136
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• Simulations of Electron Beam Interactions in Brown Dwarf Atmospheres
• Disentangling auroral, cloud and magnetic spot driven variability in three early L-dwarfs with HST/WFC3
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