Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-resolution Data

The formation and evolution pathway for the directly imaged multiplanetary system HR 8799 remains mysterious. Accurate constraints on the chemical composition of the planetary atmosphere(s) are key to solving the mystery. We perform a detailed atmospheric retrieval on HR 8799 c to infer the chemical...

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Published in:The Astronomical journal 2023-01, Vol.165 (1), p.4
Main Authors: Wang, Ji, Wang, Jason J., Ruffio, Jean-Baptiste, Blake, Geoffrey A., Mawet, Dimitri, Baker, Ashley, Bartos, Randall, Bond, Charlotte Z., Calvin, Benjamin, Cetre, Sylvain, Delorme, Jacques-Robert, Doppmann, Greg, Echeverri, Daniel, Finnerty, Luke, Fitzgerald, Michael P., Jovanovic, Nemanja, Lopez, Ronald, Martin, Emily C., Morris, Evan, Pezzato, Jacklyn, Ragland, Sam, Ruane, Garreth, Sappey, Ben, Schofield, Tobias, Skemer, Andrew, Venenciano, Taylor, Wallace, J. Kent, Wizinowich, Peter, Xuan, Jerry W., Bryan, Marta L., Roy, Arpita, Wallack, Nicole L.
Format: Article
Language:English
Subjects:
Abundance
Astronomy
Chemical composition
Deposition
Exoplanet atmospheres
Gas giant planets
Planet formation
Planetary atmospheres
Planetary composition
Planets
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Summary:The formation and evolution pathway for the directly imaged multiplanetary system HR 8799 remains mysterious. Accurate constraints on the chemical composition of the planetary atmosphere(s) are key to solving the mystery. We perform a detailed atmospheric retrieval on HR 8799 c to infer the chemical abundances and abundance ratios using a combination of photometric data along with low- and high-resolution spectroscopic data ( R ∼ 20–35,000). We specifically retrieve [C/H], [O/H], and C/O and find them to be 0.55 − 0.39 + 0.36 , 0.47 − 0.32 + 0.31 , and 0.67 − 0.15 + 0.12 at 68% confidence. The superstellar C and O abundances, yet a stellar C/O ratio, reveal a potential formation pathway for HR 8799 c. Planet c, and likely the other gas giant planets in the system, formed early on (likely within ∼1 Myr), followed by further atmospheric enrichment in C and O through the accretion of solids beyond the CO ice line. The enrichment either preceded or took place during the early phase of the inward migration to the current planet locations.
ISSN:0004-6256
1538-3881
DOI:10.3847/1538-3881/ac9f19