2022RNAAS...6..194Z

Chemical and isotopic composition provide insights into the formation and evolution history of planets and brown dwarfs. Recent measurements of ¹²CO/¹³CO abundance ratios in the atmosphere of the young super-Jupiter YSES-1b and the isolated brown dwarf 2MASS J03552337+1133437 may point to distinct formation pathways. Here we present our analysis of 0.5 hr of science verification observations using the recently upgraded CRIRES spectrograph at ESO's Very Large Telescope on the same brown dwarf, with the aim to detect C¹⁸O and determine the ¹⁶O/¹⁸O isotope ratio. Our free retrieval analyses confirm the previous measurement of the carbon isotope ratio, and the inclusion of the C¹⁸O molecule in our models enables an initial tentative constraint of ¹⁶O/¹⁸O = ${1489}_{-426}^{+1027}$ on the oxygen isotope ratio, but this requires more data to be confirmed. These short observations showcase the prospect of studying the isotope inventory in brown dwarfs and super-Jovian exoplanets with high-dispersion spectroscopy.