The ESO SupJup Survey

Astronomy and Astrophysics, vol. 709, pp. A141

Abstract

Context . Emerging research suggests that elemental and isotopic ratios of exoplanet and brown dwarf atmospheres may serve as potential tracers of their formation pathways. The ESO SupJup Survey aims to shed light on this hypothesis, with a focus on the 12 CO/ 13 CO ratio, by investigating the atmospheric composition of substellar companions and isolated brown dwarfs. Aims . In this work, we aim to characterize the atmospheres and determine the ratios of 12 CO/ 13 CO of the Rho Ophiuchus X-ray source (ROXs) 12 system (∼6 Myr), consisting of an M0 host with an L0 companion, as part of the ESO SupJup survey. This system provides a great opportunity to directly compare the atmospheric compositions of the host star and its companion. Methods . Using high-resolution CRIRES+ K band spectra of these objects, we perform atmospheric retrieval analyses to derive their atmospheric properties, including the 12 CO/ 13 CO ratio. Our retrieval framework is built on the radiative transfer code petitRADTRANS , with which we generate model spectra based on equilibrium chemistry tables computed with FastChem, coupled with the nested sampling algorithm PyMultiNest . Results . We report the presence of H 2 O, 12 CO, 13 CO, and HF in both the star and companion, with a tentative detection of H 18 2 O in ROXs 12B. The 12 CO/ 13 CO ratios of the two objects show a measurable, though not strongly significant, difference, namely 77 −7 +10 and 55 −7 +10 for ROXs 12A and B. Both are consistent with the local present interstellar medium. We measure a C/O ratio of 0.54 ± 0.01 and obtain a lower limit of H 16 2 O/H 18 2 O ⪆ 300 for ROXs 12B, while the C/O ratio of the star is not reliably constrained due to the absence of atomic oxygen lines in the K band. The companion also appears to exhibit a more isothermal temperature structure than expected from models. Furthermore, we retrieve moderate veiling in the host star of r k = 0.17 −0.03 +0.02 . Conclusions . Systems such as ROXs 12, in which both star and planet can be chemically and isotopically characterized, are crucial for constraining potential formation mechanisms of massive, wide-orbit super-Jupiters. The differing 12 CO/ 13 CO ratios in the ROXs 12 system highlight the need for a broader sample to assess the frequency of isotopic variations and whether they may be linked to formation history.

Authors 10

1. Natalie Grasser Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

2. Ignas A. G. Snellen Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

3. S. de Regt Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

4. D. González Picos Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

5. Y. Z. Zhang

   California Institute of Technology

   Affiliation as printed

   Department of Astronomy, California Institute of Technology

6. T. Stolker Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

7. Siddharth Gandhi

   University of Warwick

   Affiliation as printed

   Centre for Exoplanets and Habitability, University of Warwick

   Department of Physics, University of Warwick

8. R. Landman Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University

9. P. Mollière

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie

10. N. F. Allard

    Centre National de la Recherche Scientifique · Université Paris Sciences et Lettres · Observatoire de Paris · Institut d'Astrophysique de Paris · Sorbonne Université · Sorbonne Paris Cité

    Affiliation as printed

    Institut d’Astrophysique de Paris, UMR7095, CNRS, Université Paris VI

    LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Sorbonne Paris Cité