Zhang, Z., Mukherjee, S., Liu, M. C., Fortney, J. J., Mader, E., Best, W. M. J., Dupuy, T. J., Leggett, S. K., Karalidi, T., Line, M. R., Marley, M. S., Morley, C. V., Phillips, M. W., Siverd, R. J., & Zalesky, J. A. (2024). Disequilibrium Chemistry, Diabatic Thermal Structure, and Clouds in the Atmosphere of COCONUTS-2b. The Astronomical Journal, (Submitted).
This study aims to characterize the atmospheric properties of COCONUTS-2b, a planetary-mass companion orbiting the young M3 star COCONUTS-2A, using newly acquired near-infrared spectroscopy and existing photometric data. The authors investigate the presence of disequilibrium chemistry, a diabatic thermal structure, and clouds in the planet's atmosphere.
The researchers obtained high-quality near-infrared spectra of COCONUTS-2b using the Gemini/Flamingos-2 spectrograph. They compared these spectra with a library of T/Y dwarf spectral templates to refine the object's spectral type. To constrain the atmospheric properties, they conducted an extensive forward-modeling analysis, comparing the observed spectrum and broadband photometry with sixteen state-of-the-art atmospheric model grids for brown dwarfs and self-luminous exoplanets.
The findings indicate that COCONUTS-2b's atmosphere exhibits disequilibrium chemistry, potentially influenced by vertical mixing processes. The presence of a diabatic thermal structure and/or clouds further shapes its atmospheric properties. The derived atmospheric parameters provide valuable constraints for understanding the formation and evolution of this unique planetary-mass companion.
This research contributes to the growing body of knowledge about the atmospheric characteristics of wide-orbit planetary-mass companions. The study highlights the importance of considering disequilibrium chemistry, non-adiabatic processes, and cloud formation in modeling the atmospheres of such objects. The findings have implications for understanding the diversity of exoplanet atmospheres and the potential formation pathways of wide-orbit companions.
The study acknowledges uncertainties in the alkali chemistry models and opacities, particularly in the Y band. Future observations with JWST and other telescopes will provide more detailed spectroscopic data, enabling further refinement of atmospheric models and a deeper understanding of the chemical and physical processes shaping COCONUTS-2b's atmosphere.
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by Zhoujian Zha... at arxiv.org 10-16-2024
https://arxiv.org/pdf/2410.10939.pdfDeeper Inquiries