The ESO SupJup Survey

Astronomy and Astrophysics, vol. 688, pp. A116

Abstract

Context . It has been proposed that the distinct formation and evolutionary pathways of exoplanets and brown dwarfs may affect the chemical and isotopic content of their atmospheres. Recent work has indeed shown differences in the 12 C/ 13 C isotope ratio, which have provisionally been attributed to the top-down formation of brown dwarfs and the core accretion pathway of super-Jupiters. Aims . The ESO SupJup Survey is aimed at disentangling the formation pathways of isolated brown dwarfs and planetary-mass companions using chemical and isotopic tracers. The survey utilises high-resolution spectroscopy with the recently upgraded CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES + ) at the Very Large Telescope, covering a total of 49 targets. Here, we present the first results of this survey: an atmospheric characterisation of DENIS J0255-4700, an isolated brown dwarf near the L-T transition. Methods . We analysed its observed CRIRES + K -band spectrum using an atmospheric retrieval framework in which the radiative transfer code petitRADTRANS was coupled with the PyMultiNest sampling algorithm. Gaussian processes were employed to model inter-pixel correlations. In addition, we adopted an updated parameterisation of the pressure-temperature profile. Results . Abundances of CO, H 2 O, CH 4 , and NH 3 were retrieved for this fast-rotating L-dwarf. The ExoMol H 2 O line list provides a significantly better fit than that of HITEMP. A free-chemistry retrieval is strongly favoured over equilibrium chemistry, caused by an under-abundance of CH 4 . The free-chemistry retrieval constrains a super-solar C/O-ratio of ~0.68 and a solar metallicity. We find tentative evidence (~3 σ ) for the presence of 13 CO, with a constraint on the isotopologue ratio of 12 CO/ 13 CO = 184 −40 +61 and a lower limit of ≳97, which suggests a depletion of 13 C compared to the local interstellar medium ( 12 C/ 13 C ~ 68). Conclusions . High-resolution, high signal-to-noise K -band spectra provide an excellent means of constraining the chemistry and isotopic content of sub-stellar objects, which is the main objective of the ESO SupJup Survey.

Authors 12

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Rico Landman Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

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

9. P. Mollière

   Max Planck Institute for Astronomy

   Affiliation as printed

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

10. E. Nasedkin

    Max Planck Institute for Astronomy

    Affiliation as printed

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

11. A. Sánchez-López

    Instituto de Astrofísica de Andalucía

    Affiliation as printed

    Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain

12. T. Stolker Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

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