The GAPS Programme at TNG XXXIX. Multiple Molecular Species in the Atmosphere of the Warm Giant Planet WASP-80 b Unveiled at High Resolution with GIANO-B ^∗

Abstract

Detections of molecules in the atmosphere of gas giant exoplanets allow us to investigate the physico-chemical properties of the atmospheres. Their inferred chemical composition is used as tracer of planet formation and evolution mechanisms. Currently, an increasing number of detections is showing a possible rich chemistry of the hotter gaseous planets, but whether this extends to cooler giants is still unknown. We observed four transits of WASP-80 b, a warm transiting giant planet orbiting a late-K dwarf star with the near-infrared GIANO-B spectrograph installed at the Telescopio Nazionale Galileo and performed high-resolution transmission spectroscopy analysis. We report the detection of several molecular species in its atmosphere. Combining the four nights and comparing our transmission spectrum to planetary atmosphere models containing the signature of individual molecules within the cross-correlation framework, we find the presence of H2O, CH4, NH3, and HCN with high significance, tentative detection of CO2, and inconclusive results for C2H2 and CO. A qualitative interpretation of these results, using physically motivated models, suggests an atmosphere consistent with solar composition and the presence of disequilibrium chemistry and we therefore recommend the inclusion of the latter in future modeling of sub-1000 K planets.

Chemical Diversity in Protoplanetary Disks and Its Impact on the Formation History of Giant Planets

“…These results expand those of Paper I, showing how the relative values of the normalized ratios follow the same patterns independently on the underlying chemical scenario. These behaviors have been recently confirmed in the studies of Biazzo et al (2022), Carleo et al (2022), andGuilluy et al (2022), based on Paper I.…”

“…For instance, observations by Giacobbe et al (2021) of the hot Jupiter HD 209458b, at the equilibrium temperature of 1500 K, revealed the presence of H 2 O, CO, HCN, CH 4 , NH 3 , and C 2 H 2 in the atmosphere. Carleo et al (2022) and Guilluy et al (2022) have recently extended this result to giant planets with equilibrium temperature T 1000 K. Future observations with JWST (Greene et al 2016), Twinkle (Edwards et al 2019b), and Ariel (Tinetti et al 2018), as well as advances in atmospheric retrieval techniques, will soon revolutionize the field. The broad spectral range and the high spectral resolution of JWST will allow for precise determination of the abundances of a number of species of interest besides H 2 O, like CO, CO 2 , CH 4 , and NH 3 (Greene et al 2016).…”

“…If, instead, the planet formed around a star characterized by a subsolar C/O ratio (e.g., 0.45), the planetary C/O ratio should be correctly interpreted as superstellar. Our methodology has been recently successfully applied by Carleo et al (2022) and Guilluy et al (2022) to the interpretation of observational data from the GAPS 2 program.…”

“…Recent studies have validated our methodology on real data in preparation of its use for interpreting the observations of future ground-based and space-based facilities. Alongside Carleo et al (2022) and Guilluy et al (2022), Biazzo et al (2022) put constraints on possible formation scenarios for the giant planets in four planetary systems, around the stars HAT-P-26, WASP-39, HAT-P-12, and WASP-10. Specifically, they analyzed the trends of the normalized planetary metallicity and elemental ratios based on the atmospheric composition obtained by Kawashima & Min (2021) through spectral disequilibrium retrieval models.…”

“…A similar study was performed independently by Kolecki & Wang (2022) on an additional set of four giant planets. As discussed before, Carleo et al (2022) and Guilluy et al (2022) jointly used the planetary metallicity and the C/O * ratio to constrain the formation histories of WASP-69b and WASP-80b, as well as the characteristics of their native circumstellar disks (see also Section 3.3). More systematic studies of the observational implications of our results will be the focus of dedicated future works.…”