Time-resolved absorption of six chemical species with MAROON-X points to a strong drag in the ultra-hot Jupiter TOI-1518 b

¹ Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Nice, France
² Institut Trottier de Recherche sur les Exoplanètes, Université de Montréal, Montréal, Québec H3T 1J4, Canada
³ Tsung-Dao Lee Institute, Shanghai Jiao Tong University, 520 Shengrong Road, Shanghai, PR China
⁴ School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, PR China
⁵ Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁶ Lund Observatory, Department of Astronomy and Theoretical Physics, Department of Physics, Lund University, Lund, Sweden
⁷ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Región Metropolitana, Chile
⁸ Department of Astronomy & Astrophysics, University of Chicago, Chicago, IL 60637, USA
⁹ Observatoire de Haute-Provence, CNRS, Université d’Aix-Marseille, 04870 Saint-Michel-l’Observatoire, France
¹⁰ School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281, USA
¹¹ Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
¹² Observatoire astronomique de l’Université de Genève, 51 chemin Pegasi 1290 Versoix, Switzerland
¹³ Gemini Observatory/NSF NOIRLab, 670 N. A’ohoku Place, Hilo, HI 96720, USA
¹⁴ Univ. Grenoble Alpes, CNRS, IPAG, 414 rue de la Piscine, 38400 St-Martin d’Hères, France
¹⁵ Department of Physics, University of Turin, Via Pietro Giuria 1, 10125 Turin, Italy
¹⁶ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
¹⁷ Anton Pannekoek Institute of Astronomy, University of Amsterdam, Amsterdam, The Netherlands
¹⁸ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
¹⁹ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
²⁰ Atmospheric, Oceanic, and Planetary Physics, Department of Physics, University of Oxford, Parks Rd, Oxford OX1 3PU, UK
²¹ Université de Toulouse, CNRS, IRAP, 14 avenue Belin, 31400 Toulouse, France
²² LESIA, Observatoire de Paris, Univ PSL, CNRS, Sorbonne Univ, Univ de Paris, 5 place Jules Janssen, 92195 Meudon, France
²³ INAF-Osservatorio Astrofisico di Arcetri Largo Enrico Fermi, Florence, Italy
²⁴ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
²⁵ Steward Observatory, University of Arizona, Tucson, AZ, USA
²⁶ International Center for Advanced Studies (ICAS) and ICIFI (CONICET), ECyT-UNSAM, Campus Miguelete, 25 de Mayo y Francia, 1650 Buenos Aires, Argentina

^★ Corresponding author: adrien.simonnin@oca.eu

Received: 30 November 2024
Accepted: 8 April 2025

Abstract

Context. Wind dynamics play a pivotal role in governing transport processes within planetary atmospheres, influencing atmospheric chemistry, cloud formation, and the overall energy budget. Understanding the strength and patterns of winds is crucial for comprehensive insights into the physics of ultra-hot-Jupiter atmospheres. Current research has proposed different mechanisms that limit wind speeds in these atmospheres.

Aims. This study focuses on unraveling the wind dynamics and the chemical composition in the atmosphere of the ultra-hot Jupiter TOI-1518 b.

Methods. Two transit observations using the high-resolution (R_λ ∼ 85 000) optical (spectral coverage between 490 and 920 nm) spectrograph MAROON-X were obtained and analyzed to explore the chemical composition and wind dynamics using the cross-correlation techniques, global circulation models (GCMs), and atmospheric retrieval.

Results. We report the detection of 14 species in the atmosphere of TOI-1518 b through cross-correlation analysis. VO was detected only with the new HyVO line list, whereas TiO was not detected. Additionally, we measured the time-varying cross-correlation trails for six different species, compared them with predictions from GCMs, and conclude that a strong drag is slowing the winds in TOI-1518 b’s atmosphere (τ_drag ≈ 10³−10⁴ s). We find that the trails are species dependent. Fe+ favors stronger drag than Fe, which we interpret as a sign of magnetic effects being responsible for the observed strong drag. Furthermore, we show that Ca+ probes layers above the Roche lobe, leading to a qualitatively different trail than the other species. Finally, We used a retrieval analysis to further characterize the abundances of the different species detected. Our analysis is refined thanks to the updated planetary mass of 1.83 ± 0.47 M_Jup we derived from new Sophie radial-velocity observations. We measure an abundance of Fe of log₁₀ Fe = −4.88_−0.76^+0.63 corresponding to 0.07 to 1.62 solar enrichment. For the other elements, the retrievals appear to be biased, probably due to the different K_p/V_sys shifts between Fe and the other elements, which we demonstrate for the case of VO.