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

Abstract

We present Gemini South/IGRINS observations of the 1060 K T6 dwarf 2MASS J08173001$-$6155158 with unprecedented resolution ($R\equiv \lambda /\Delta \lambda =45000$) and signal-to-noise ratio (SNR > 200) for a late-type T dwarf. We use this benchmark observation to test the reliability of molecular line lists used up-to-date atmospheric models. We determine which spectroscopic regions should be used to estimate the parameters of cold brown dwarfs and, by extension, exoplanets. We present a detailed spectroscopic atlas with molecular identifications across the $H$ and $K$ bands of the near-infrared. We find that water (H${}_2$O) line lists are overall reliable. We find the most discrepancies amongst older methane (CH${}_4$) line lists, and that the most up-to-date CH${}_4$ line lists correct many of these issues. We identify individual ammonia (NH${}_3$) lines, a hydrogen sulfide (H${}_2$S) feature at 1.5900 $\mu$m, and a molecular hydrogen (H${}_2$) feature at 2.1218 $\mu$m. These are the first unambiguous detections of H${}_2$S and H${}_2$ absorption features in an extra-solar atmosphere. With the H${}_2$ detection, we place an upper limit on the atmospheric dust concentration of this T6 dwarf: at least 500 times less than the interstellar value, implying that the atmosphere is effectively dust-free. We additionally identify several features that do not appear in the model spectra. Our assessment of the line lists is valuable for atmospheric model applications to high-dispersion, low-SNR, high-background spectra, such as an exoplanet around a star. We demonstrate a significant enhancement in the detection of the CH${}_4$ absorption signal in this T6 dwarf with the most up-to-date line lists.

45 pages, 63 figures, 5 tables, Accepted to MNRAS

References in corpus (26)

• The Gaia mission
• Improved parameters for extrasolar transiting planets
• The fast spin-rotation of a young extrasolar planet
• Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres
• Synthetic Spectra and Colors of Young Giant Planet Atmospheres: Effects of Initial Conditions and Atmospheric Metallicity
• ExoMol molecular line lists XXXV: a rotation-vibration line list for hot ammonia
• An accurate, extensive, and practical line list of methane for the HITEMP database
• Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs
• A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere
• Five carbon- and nitrogen-bearing species in a hot giant planet's atmosphere
• ExoMol line lists VII: The rotation-vibration spectrum of phosphine up to 1500 K
• Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs I: Characterizing Benchmarks, Gl570D and HD3651B
• Hubble Space Telescope Spectroscopy of Brown Dwarfs Discovered with the Wide-field Infrared Survey Explorer
• The full infrared spectrum of molecular hydrogen
• Exoplanet atmospheres with GIANO II. Detection of molecular absorption in the dayside spectrum of HD 102195b
• Observations of Disequilibrium CO Chemistry in the Coldest Brown Dwarfs
• A Uniform Retrieval Analysis of Ultracool Dwarfs. III. Properties of Y-Dwarfs
• Probable detection of hydrogen sulphide (H${}_2$S) in Neptune's atmosphere
• Sparkling nights and very hot days on WASP-18b: the formation of clouds and the emergence of an ionosphere
• Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-Cool Dwarfs
• Methane and Ammonia in the near-infrared spectra of late T dwarfs
• 3.8um Imaging of 400-600K Brown Dwarfs and Orbital Constraints for WISEP J045853.90+643452.6AB
• An Improved Near-Infrared Spectrum of the Archetype Y Dwarf WISEP J182831.08+265037.8
• 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
• IGRINS RV: A Precision RV Pipeline for IGRINS Using Modified Forward Modeling in the Near-Infrared
• The Sonora Brown Dwarf Atmosphere and Evolution Models I. Model Description and Application to Cloudless Atmospheres in Rainout Chemical Equilibrium

Cited by in corpus (14)

• The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultra Hot Jupiter WASP-18 b
• Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry
• The ESO SupJup Survey I: Chemical and isotopic characterisation of the late L-dwarf DENIS J0255-4700 with CRIRES${}^{+}$
• The cool brown dwarf Gliese 229 B is a close binary
• Global weather map reveals persistent top-of-atmosphere features on the nearest brown dwarfs
• An Interpretable Machine Learning Framework for Modeling High-Resolution Spectroscopic Data
• The puzzle of the formation of T8 dwarf Ross 458c
• The ESO SupJup Survey VIII. Chemical fingerprints of young L dwarf twins
• 10 Years of Archival High-Resolution NIR Spectra: The Raw and Reduced IGRINS Spectral Archive (RRISA)
• The HITRAN2024 methane update
• Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
• Atmospheric retrieval of Subaru/IRD high-resolution spectrum of the archetype T-type brown dwarf Gl 229 B
• A 1.48-2.48 $\mu$m R=28000 spectroscopic atlas of the L7.5 and T0.5 components of the nearest pair of brown dwarfs: Luhman 16AB
• Silicate Clouds, SiO, and Molecular Trends across the L-T Sequence: A JWST/MIRI LRS Spectral Library of Brown Dwarfs