The ESO SupJup Survey

Astronomy and Astrophysics, vol. 693, pp. A298

Abstract

Context . The carbon isotope ratio ( 12 C/ 13 C) is a potential tracer of giant planet and brown dwarf formation. The GQ Lup system, which hosts the K7 T Tauri star GQ Lup A and its substellar companion GQ Lup B, provides a unique opportunity to investigate 12 C/ 13 C in a young system. Aims . We aim to characterise GQ Lup B’s atmosphere, determining its temperature, chemical composition, spin, surface gravity, and 12 C/ 13 C, while also measuring the 12 C/ 13 C of its host star, GQ Lup A. Methods . We obtained high-resolution K -band spectra of GQ Lup using CRIRES + at the VLT. We modelled GQ Lup A’s starlight contribution and fitted GQ Lup B’s spectrum using atmospheric models from petitRADTRANS . The 12 C/ 13 C ofGQ Lup A was derived using isotope-dependent PHOENIX models. Results . We measured atmospheric abundances in GQ Lup B, including H 2 O, 12 CO, 13 CO, HF, Na, Ca, and Ti, and determined a C/O ratio of 0.50 ± 0.01, which is consistent with the solar value. The carbon isotope ratio is 12 C/ 13 C = 53 −6 +7 for GQ Lup B and 51 −8 +10 for GQ Lup A. Strong veiling of GQ Lup A’s photospheric lines was also identified and accounted for. Conclusions . The similar 12 C/ 13 C values in GQ Lup A and B suggest a common origin from a shared material reservoir, supporting the idea of formation via disc fragmentation or gravitational collapse.

Authors 7

1. D. González Picos Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. 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, P.O. 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, P.O. Box 9513, 2300 RA, Leiden, The Netherlands

4. Rico Landman Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. 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, P.O. 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, P.O. Box 9513, 2300 RA, Leiden, The Netherlands

7. 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