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

TL;DR

This study characterizes the ultra-hot Jupiter TOI-1431b, revealing a misaligned polar orbit and an absence of detectable atomic or molecular atmospheric features, likely due to its high surface gravity.

Contribution

First detailed atmospheric analysis of TOI-1431b, demonstrating a polar orbit and no detectable atmospheric absorption features using high-resolution spectroscopy.

Findings

Planet has a polar orbit with a projected obliquity of -155°.

No evidence of common atomic or molecular absorptions in the atmosphere.

Large surface gravity likely explains the absence of atmospheric features.

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-1431b/MASCARA-5b, 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 $ \lambda = -155^{+20}_{-10}$ degrees. Combining the nights and applying both cross-correlation methods and transmission spectroscopy, we find no evidences of CaI, FeI, FeII, MgI, NaI, VI, TiO, VO or H$\alpha$ in the atmosphere of the planet. Our most likely explanation for the lack of atmospheric features is the large surface gravity of the planet.