TY - JOUR
T1 - High-precision Atmospheric Characterization of a Y Dwarf with JWST NIRSpec G395H Spectroscopy
T2 - Isotopologue, C/O Ratio, Metallicity, and the Abundances of Six Molecular Species
AU - Lew, Ben W.P.
AU - Roellig, Thomas
AU - Batalha, Natasha E.
AU - Line, Michael
AU - Greene, Thomas
AU - Murkherjee, Sagnick
AU - Freedman, Richard
AU - Meyer, Michael
AU - Beichman, Charles
AU - Alves de Oliveira, Catarina
AU - De Furio, Matthew
AU - Johnstone, Doug
AU - Greenbaum, Alexandra Z.
AU - Marley, Mark
AU - Fortney, Jonathan J.
AU - Young, Erick T.
AU - Leisenring, Jarron
AU - Boyer, Martha
AU - Hodapp, Klaus
AU - Misselt, Karl
AU - Stansberry, John
AU - Rieke, Marcia
N1 - Publisher Copyright:
© 2024. The Author(s). Published by the American Astronomical Society.
PY - 2024/5/1
Y1 - 2024/5/1
N2 - The launch of the James Webb Space Telescope (JWST) marks a pivotal moment for precise atmospheric characterization of Y dwarfs, the coldest brown dwarf spectral type. In this study, we leverage moderate spectral resolution observations (R ∼ 2700) with the G395H grating of the Near-Infrared Spectrograph (NIRSpec) on board JWST to characterize the nearby (9.9 pc) Y dwarf WISEPA J182831.08+265037.8. With the NIRSpec G395H 2.88-5.12 μm spectrum, we measure the abundances of CO, CO2, CH4, H2S, NH3, and H2O, which are the major carbon-, nitrogen-, oxygen-, and sulfur-bearing species in the atmosphere. Based on the retrieved volume mixing ratios with the atmospheric retrieval framework CHIMERA, we report that the C/O ratio is 0.45 ± 0.01, close to the solar C/O value of 0.458, and the metallicity is +0.30 ± 0.02 dex. Comparison between the retrieval results and the forward modeling results suggests that the model bias for C/O and metallicity could be as high as 0.03 and 0.97 dex, respectively. We also report a lower limit of the 12CO/13CO ratio of >40, being consistent with the nominal solar value of 90. Our results highlight the potential for JWST to measure the C/O ratios down to percent-level precision and characterize isotopologues of cold planetary atmospheres similar to WISE 1828.
AB - The launch of the James Webb Space Telescope (JWST) marks a pivotal moment for precise atmospheric characterization of Y dwarfs, the coldest brown dwarf spectral type. In this study, we leverage moderate spectral resolution observations (R ∼ 2700) with the G395H grating of the Near-Infrared Spectrograph (NIRSpec) on board JWST to characterize the nearby (9.9 pc) Y dwarf WISEPA J182831.08+265037.8. With the NIRSpec G395H 2.88-5.12 μm spectrum, we measure the abundances of CO, CO2, CH4, H2S, NH3, and H2O, which are the major carbon-, nitrogen-, oxygen-, and sulfur-bearing species in the atmosphere. Based on the retrieved volume mixing ratios with the atmospheric retrieval framework CHIMERA, we report that the C/O ratio is 0.45 ± 0.01, close to the solar C/O value of 0.458, and the metallicity is +0.30 ± 0.02 dex. Comparison between the retrieval results and the forward modeling results suggests that the model bias for C/O and metallicity could be as high as 0.03 and 0.97 dex, respectively. We also report a lower limit of the 12CO/13CO ratio of >40, being consistent with the nominal solar value of 90. Our results highlight the potential for JWST to measure the C/O ratios down to percent-level precision and characterize isotopologues of cold planetary atmospheres similar to WISE 1828.
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U2 - 10.3847/1538-3881/ad3425
DO - 10.3847/1538-3881/ad3425
M3 - Article
AN - SCOPUS:85191339430
SN - 0004-6256
VL - 167
JO - Astronomical Journal
JF - Astronomical Journal
IS - 5
M1 - 237
ER -