Mapping the Cloud-Driven Atmospheric Dynamics & Chemistry of an Isolated Exoplanet Analog with Harmonic Signatures
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arXiv
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| Natura: | Preprint |
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2025
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| author | Plummer, Michael K. Cocchini, Francis P. Kearns, Peter A. McCarthy, Allison Artigau, Étienne Cowan, Nicolas B. Akhmetshyn, Roman Vos, Johanna Nasedkin, Evert Visscher, Channon Benneke, Björn Doyon, René Metchev, Stanimir A. Rowe, Jason F. Suárez, Genaro |
| author_facet | Plummer, Michael K. Cocchini, Francis P. Kearns, Peter A. McCarthy, Allison Artigau, Étienne Cowan, Nicolas B. Akhmetshyn, Roman Vos, Johanna Nasedkin, Evert Visscher, Channon Benneke, Björn Doyon, René Metchev, Stanimir A. Rowe, Jason F. Suárez, Genaro |
| contents | Young planetary-mass objects and brown dwarfs near the L/T spectral transition exhibit enhanced spectrophotometric variability over field brown dwarfs. Patchy clouds, auroral processes, stratospheric hot spots, and complex carbon chemistry have all been proposed as potential sources of this variability. Using time-resolved, low-to-mid-resolution spectroscopy collected with the JWST/NIRISS and NIRSpec instruments, we apply harmonic analysis to SIMP J013656.5+093347, a highly variable, young, isolated planetary-mass object. Odd harmonics (k = 3) at pressure levels ~ 1 bar, corresponding to iron and forsterite cloud formation, suggest a potential North-South hemispheric asymmetry in the cloudy, and likely equatorial, regions. We use the inferred harmonics, along with 1-D substellar atmospheric models, to map the flux variability by atmospheric pressure level. We identify distinct time-varying structures in the near-infrared that we interpret as planetary-scale wave (e.g., Rossby or Kelvin)-associated cloud modulation. We detect deviations from bulk (composite) variability in water (S/N = 14.0), carbon monoxide (S/N = 13.0), and methane (S/N = 14.9) molecular signatures. Forsterite cloud modulation is anti-correlated with overlying carbon monoxide and water abundances and correlated with deep methane absorption, suggesting complex interaction between cloud formation, atmospheric chemistry, and temperature structure. Furthermore, we identify distinct harmonic behavior between methane and carbon monoxide absorption bands, providing evidence for time-resolved disequilibrium carbon chemistry. At the lowest pressures (< 100 mbar), we find mapped methane lines transition from absorption to emission, supporting evidence of high-altitude auroral heating via electron precipitation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_02260 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Mapping the Cloud-Driven Atmospheric Dynamics & Chemistry of an Isolated Exoplanet Analog with Harmonic Signatures Plummer, Michael K. Cocchini, Francis P. Kearns, Peter A. McCarthy, Allison Artigau, Étienne Cowan, Nicolas B. Akhmetshyn, Roman Vos, Johanna Nasedkin, Evert Visscher, Channon Benneke, Björn Doyon, René Metchev, Stanimir A. Rowe, Jason F. Suárez, Genaro Earth and Planetary Astrophysics Solar and Stellar Astrophysics Atmospheric and Oceanic Physics Geophysics Young planetary-mass objects and brown dwarfs near the L/T spectral transition exhibit enhanced spectrophotometric variability over field brown dwarfs. Patchy clouds, auroral processes, stratospheric hot spots, and complex carbon chemistry have all been proposed as potential sources of this variability. Using time-resolved, low-to-mid-resolution spectroscopy collected with the JWST/NIRISS and NIRSpec instruments, we apply harmonic analysis to SIMP J013656.5+093347, a highly variable, young, isolated planetary-mass object. Odd harmonics (k = 3) at pressure levels ~ 1 bar, corresponding to iron and forsterite cloud formation, suggest a potential North-South hemispheric asymmetry in the cloudy, and likely equatorial, regions. We use the inferred harmonics, along with 1-D substellar atmospheric models, to map the flux variability by atmospheric pressure level. We identify distinct time-varying structures in the near-infrared that we interpret as planetary-scale wave (e.g., Rossby or Kelvin)-associated cloud modulation. We detect deviations from bulk (composite) variability in water (S/N = 14.0), carbon monoxide (S/N = 13.0), and methane (S/N = 14.9) molecular signatures. Forsterite cloud modulation is anti-correlated with overlying carbon monoxide and water abundances and correlated with deep methane absorption, suggesting complex interaction between cloud formation, atmospheric chemistry, and temperature structure. Furthermore, we identify distinct harmonic behavior between methane and carbon monoxide absorption bands, providing evidence for time-resolved disequilibrium carbon chemistry. At the lowest pressures (< 100 mbar), we find mapped methane lines transition from absorption to emission, supporting evidence of high-altitude auroral heating via electron precipitation. |
| title | Mapping the Cloud-Driven Atmospheric Dynamics & Chemistry of an Isolated Exoplanet Analog with Harmonic Signatures |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics Atmospheric and Oceanic Physics Geophysics |
| url | https://arxiv.org/abs/2510.02260 |