Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) III. Atmospheric structure of the misaligned ultra-hot Jupiter WASP-121b

Understand

Ultra-hot Jupiters offer interesting prospects for expanding our theories on dynamical evolution and the properties of extremely irradiated atmospheres.

• In this context, we present the analysis of new optical spectroscopy for the transiting ultra-hot Jupiter WASP-121b.
• We first refine the orbital properties of WASP-121b, which is on a nearly polar (obliquity $\psi^{\rm North}$=88.1$\pm$0.25$^{\circ}$ or $\psi^{\rm South}$=91.11$\pm$0.20$^{\circ}$) orbit, and exclude a high differential rotation for its fast-rotating (P$<$1.13 days), highly inclined ($i_\mathrm{\star}^{\rm North}$=8.1$\stackrel{+3.0}{_{-2.6}}^{\circ}$ or $i_\mathrm{\star}^{\rm South}$=171.9$\stackrel{+2.5}{_{-3.4}}^{\circ}$) star.
• We then present a new method that exploits the reloaded Rossiter-McLaughlin technique to separate the contribution of the planetary atmosphere and of the spectrum of the stellar surface along the transit chord.