The obliquity and atmosphere of the ultra-hot Jupiter TOI-1431b (MASCARA-5b): A misaligned orbit and no signs of atomic or molecular absorptions

¹ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
e-mail: mstangret@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, 38200 San Cristobal de La Laguna, Spain
³ Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
⁴ National Space Institute, Technical University of Denmark, Elektrovej, 2800 Kgs. Lyngby, Denmark
⁵ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
⁷ INAF – Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123 Catania, Italy
⁸ Department of Physics and Astronomy, Università degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁹ University of Southern Queensland, Centre for Astrophysics, USQ Toowoomba, West Street, QLD 4350, Australia
¹⁰ INAF – Osservatorio Astrofisico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy
¹¹ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
¹² Yale University, 52 Hillhouse Avenue, New Haven, CT 06511, USA
¹³ Fundación Galileo Galilei - INAF, Rambla José Ana Fernandez Pérez 7, 38712 Breña Baja, TF, Spain

Received: 9 December 2020
Accepted: 12 April 2021

Abstract

Ultra-hot Jupiters are defined as giant planets with equilibrium temperatures larger than 2000 K. Most of them are found orbiting bright A-F type stars, making them extremely suitable objects to study their atmospheres using high-resolution spectroscopy. Recent studies show a variety of atoms and molecules detected in the atmospheres of this type of planets. Here we present our analysis of the newly discovered ultra-hot Jupiter TOI-1431 b/MASCARA-5 b, using two transit observations with the HARPS-N spectrograph and one transit observation with the EXPRES spectrograph. Analysis of the Rossiter-McLaughlin effect shows that the planet is in a polar orbit, with a projected obliquity λ = −155₋₁₀⁺²⁰ degrees. Combining the nights and applying both cross-correlation methods and transmission spectroscopy, we find no evidences of Ca I, Fe I, Fe II, Mg I, Na I, V I, TiO, VO or Hα in the atmosphere of the planet. Our most likely explanation for the lack of atmospheric features is the large surface gravity of the planet.