The ESO SupJup Survey

Astronomy and Astrophysics, vol. 689, pp. A212

Abstract

Context . Young brown dwarfs exhibit atmospheric characteristics similar to those of super-Jupiters, providing a unique opportunity to study planetary atmospheres. Atmospheric retrievals of high-resolution spectra reveal detailed properties of these objects, with elemental and isotopic ratios offering insights into their formation history. The ESO SupJup Survey, utilising CRIRES + on the Very Large Telescope, aims to assess the role of 12 C/ 13 C as a formation tracer. Aims . We present observations of three young brown dwarfs: 2MASS J12003792-7845082, TWA 28, and 2MASS J08561384-1342242. Our goal is to constrain their chemical compositions, thermal profiles, surface gravities, spin rotations, and 12 C/ 13 C. Methods . We conducted atmospheric retrievals of CRIRES + K -band spectra, coupling the radiative transfer code petitRADTRANS with the Bayesian inference algorithm MultiNest . Results . The retrievals provide a detailed characterisation of the atmospheres of the three objects. We report the volume mixing ratios of the main molecular and atomic species: H 2 16 O, 12 CO, HF, Na, Ca, and Ti, including the novel detection of hydrogen fluoride (HF) in the atmosphere of a brown dwarf. We determine 12 C/ 13 C values of 81 −19 +28 and 79 −14 +20 in the atmospheres of TWA 28 and J0856, respectively, with strong significance (>3 σ ). We also report tentative evidence (~2 σ ) of 13 CO in J1200, at 12 C/ 13 C = 114 −33 +69 . Additionally, we detect H 2 18 O at moderate significance in J0856 (3.3 σ ) and TWA 28 (2.1 σ ). The retrieved thermal profiles are consistent with hot atmospheres (2300–2600 K) with low surface gravities and slow spins, as expected for young objects. Conclusions . The measured carbon isotope ratios are consistent among the three objects and show no significant deviation from that of the local interstellar medium, suggesting a fragmentation-based formation mechanism similar to star formation. The tentative detection of H 2 18 O in two objects of our sample highlights the potential of high-resolution spectroscopy to probe additional isotope ratios, such as 16 O/ 18 O, in the atmospheres of brown dwarfs and super-Jupiters.

Authors 10

1. D. González Picos Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

2. Ignas A. G. Snellen Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

3. S. de Regt Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

4. Rico Landman Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

5. Yapeng Zhang Aachen Leiden Observatory

   Leiden University · California Institute of Technology · Leiden Observatory

   Affiliation as printed

   Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

6. Siddharth Gandhi Aachen Leiden Observatory

   Leiden University · University of Warwick · Leiden Observatory

   Affiliation as printed

   Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK

   Department of Physics, University of Warwick, Coventry CV4 7AL, UK

   Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands

7. C. Ginski

   Ollscoil na Gaillimhe – University of Galway

   Affiliation as printed

   School of Natural Sciences, Center for Astronomy, University of Galway, Galway H91 CF50, Ireland

8. Aurora Y. Kesseli

   California Institute of Technology · Infrared Processing and Analysis Center

   Affiliation as printed

   IPAC, Mail Code 100-22, Caltech, 1200 E. California Boulevard, Pasadena, CA 91125, USA

9. P. Mollière

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

10. T. Stolker Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands