The GAPS Programme at TNG

XXXVIII. Five molecules in the atmosphere of the warm giant planet WASP-69b detected at high spectral resolution^★

¹ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
² Observatoire Astronomique de l’Université de Genève, Chemin Pegasi 51b, 1290 Versoix, Switzerland
³ Astronomy Department, Indiana University, Bloomington, IN 47405-7105, USA
⁴ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁵ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
⁶ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁷ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁸ Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
⁹ Istituto di Astrofisica e Planetologia Spaziali INAF-IAPS, Via Fosso del Cavaliere 100, 00133 Rome, Italy
¹⁰ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy
¹¹ INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
¹² Department of Physics, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
¹³ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁴ INAF – Osservatorio Astronomico di Palermo, P.zza Parlamento 1, 90134 Palermo, Italy
¹⁵ Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹⁶ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
¹⁷ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
¹⁸ Fundación G. Galilei – INAF (Telescopio Nazionale Galileo), Rambla J. A. Fernàndez Pèrez 7, 38712 Breña Baja (La Palma), Spain
¹⁹ INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Naples, Italy
²⁰ INAF – Osservatorio di Cagliari, via della Scienza 5, 09047 Selargius, CA, Italy
²¹ Dipartimento di Fisica, La Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma, Italy

Received: 24 April 2022
Accepted: 19 July 2022

Abstract

Context. The field of exo-atmospheric characterisation is progressing at an extraordinary pace. Atmospheric observations are now available for tens of exoplanets, mainly hot and warm inflated gas giants, and new molecular species continue to be detected, revealing a richer atmospheric composition than previously expected. Thanks to its warm equilibrium temperature (963 ± 18 K) and low density (0.219 ± 0.031 g cm⁻³), the close-in gas giant WASP-69b represents a golden target for atmospheric characterisation.

Aims. With the aim of searching for molecules in the atmosphere of WASP-69b and investigating its properties, we performed high-resolution transmission spectroscopy with the GIANO-B near-infrared spectrograph at the Telescopio Nazionale Galileo.

Methods. We observed three transit events of WASP-69b. During a transit, the planetary lines are Doppler-shifted due to the large change in the planet’s radial velocity, allowing us to separate the planetary signal from the quasi-stationary telluric and stellar spectrum.

Results. Considering the three nights together, we report the detection of CH₄, NH₃, CO, C₂H₂, and H₂O, at more than a 3.3a- level. We did not identify the presence of HCN or CO₂ with confidence a level higher than 3a. This is the first time that five molecules have been simultaneously detected in the atmosphere of a warm giant planet. These results suggest that the atmosphere of WASP-69b is possibly carbon-rich and characterised by the presence of disequilibrium chemistry.