The ESO SupJup Survey: VI. ¹²C/¹³C isotope ratio comparison of three L-type brown dwarfs

February 2025 • 2025A&A...694A.164M

Authors • Mulder, W. • de Regt, S. • Landman, R. • Picos, D. González • Snellen, I. A. G. • Zhang, Y. • Gandhi, S. • Ginski, C. • Kesseli, A. Y. • Nasedkin, E. • Stolker, T.

Abstract • Context. Recent research suggests that the distinct formation processes of exoplanets and brown dwarfs may have an influence on the chemical and isotopic composition of their atmospheres. Variations in the carbon ¹²C/¹³C isotope ratio have been observed and tentatively linked to the top-down formation of brown dwarfs and the core accretion pathway of super-Jupiters. The ESO SupJup Survey, conducted with CRIRES+ on the Very Large Telescope, aims to characterise the atmospheres of young brown dwarfs and super-Jupiters, specifically by investigating the ¹²C/¹³C ratio as a tracer of their formation pathways. Aims. We present the atmospheric characterisation of three isolated L-type brown dwarfs (2MASS J08354256-0819237, 2MASS J05012406-0010452, and 2MASS J05002100+0330501) included in the ESO SupJup Survey. We aim to constrain the C/O and ¹²C/¹³C ratios, and investigate whether the oxygen ¹⁶O/¹⁸O isotope ratio can be probed. Methods. We analysed the CRIRES+ K-band spectra of the three targets using our atmospheric retrieval framework. This framework couples the radiative transfer code petitRADTRANS with the sampling algorithm MultiNest. Results. We report ¹²C/¹³C ratios of 89_‑11⁺¹¹ and 117_‑17⁺²⁰ for J0835 and J0500 with strong ¹³CO significance (>6.5σ) and a tentative (3σ) detection of ¹³CO for J0501, resulting in a carbon isotope ratio of 155_‑53⁺⁵⁶. Only a weak detection of the H₂¹⁸O isotope was found in J0835. The C/O ratios are found to be in the range 0.65 to 0.71 for the three targets, and all exhibit strong detections of HF. Conclusions. The ¹²C/¹³C ratios appear to be higher than that of the interstellar medium.

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• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202452859/postscript
• PDF https://www.aanda.org/10.1051/0004-6361/202452859/pdf
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202452859