Silicon in the dayside atmospheres of two ultra-hot Jupiters

TL;DR

This study reports the first detection of neutral silicon in the atmospheres of two ultra-hot Jupiters using high-resolution spectroscopy, revealing inverted temperature profiles and implications for cloud formation.

Contribution

It provides the first evidence of silicon in exoplanet atmospheres and confirms temperature inversions in ultra-hot Jupiters through Doppler spectroscopy.

Findings

Detection of Si spectral signature at 4.8σ and 5.4σ levels.

Confirmation of temperature inversion in both planets.

Implications for cloud formation processes.

Abstract

Atmospheres of highly irradiated gas giant planets host a large variety of atomic and ionic species. Here we observe the thermal emission spectra of the two ultra-hot Jupiters WASP-33b and KELT-20b/MASCARA-2b in the near-infrared wavelength range with CARMENES. Via high-resolution Doppler spectroscopy, we searched for neutral silicon (Si) in their dayside atmospheres. We detect the Si spectral signature of both planets via cross-correlation with model spectra. Detection levels of 4.8$\mathrm{\sigma}$ and 5.4$\mathrm{\sigma}$, respectively, are observed when assuming a solar atmospheric composition. This is the first detection of Si in exoplanet atmospheres. The presence of Si is an important finding due to its fundamental role in cloud formation and, hence, for the planetary energy balance. Since the spectral lines are detected in emission, our results also confirm the presence of an inverted temperature profile in the dayside atmospheres of both planets.