Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths

TL;DR

This paper models the emission spectra of hot rocky super-Earths with magma ocean atmospheres, predicting detectable SiO features in their thermal emission spectra for upcoming space telescopes.

Contribution

It provides the first detailed radiative transfer calculations of magma ocean atmospheres, identifying key spectral features and thermal structures.

Findings

Thermal inversion caused by SiO UV absorption.

Detectable SiO emission features at 4, 10, and 100 micrometers.

Potential for future space telescopes to observe these features.

Abstract

Motivated by recent detection of transiting high-density super-Earths, we explore the detectability of hot rocky super-Earths orbiting very close to their host stars. In the environment hot enough for their rocky surfaces to be molten, they would have the atmosphere composed of gas species from the magma oceans. In this study, we investigate the radiative properties of the atmosphere that is in the gas/melt equilibrium with the underlying magma ocean. Our equilibrium calculations yield Na, K, Fe, Si, SiO, O, and O$_2$ as the major atmospheric species. We compile the radiative-absorption line data of those species available in literature, and calculate their absorption opacities in the wavelength region of 0.1--100~$\mathrm{\mu m}$. Using them, we integrate the thermal structure of the atmosphere. Then, we find that thermal inversion occurs in the atmosphere because of the UV absorption by SiO. In addition, we calculate the ratio of the planetary to stellar emission fluxes during secondary eclipse, and find prominent emission features induced by SiO at 4~$\mathrm{\mu m}$ detectable by Spitzer, and those at 10 and 100~$\mathrm{\mu m}$ detectable by near-future space telescopes.