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

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.