Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths

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 µm. 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 µm detectable by Spitzer, and those at 10 and 100 µm detectable by near-future space telescopes.

A Search for Water in a Super-Earth Atmosphere: High-resolution Optical Spectroscopy of 55Cancri e

“…As a result, Lammer et al (2013) conclude that one can expect that 55Cnce would not lose its hydrogen envelope during its remaining lifetime. Demory et al (2012) report a Spitzer secondary eclipse depth of 131±28 ppm corresponding to a brightness temperature of 2360±300 K. Ito et al (2015) find that this brightness temperature is in agreement with the theoretically predicted eclipse depth created by a mineral atmosphere on 55Cnc e. Their study investigates the radiative properties of an atmosphere that is in gas/melt equilibrium with the underlying magma ocean. Their equilibrium calculations yielded a mineral atmosphere (i.e., Na, K, Fe, Si, SiO, O, and O 2 as the major atmospheric species), and radiative absorption line data was used to calculate theoretical eclipse depths.…”

“…Additional evidence includes the tentative detection of sodium and singly ionized calcium reported by Ridden-Harper et al (2016), as well as findings from Lammer et al (2013) that 55Cnce's theoretical mass-loss rate is ∼10 times lower than that of a typical hot-Jupiter, and therefore 55Cnce can retain a hydrogen envelope. Furthermore, a water-depleted atmosphere was predicted by Ito et al (2015), who modeled an atmosphere that is in gas/melt equilibrium with an underlying magma ocean; a possible scenario for 55Cnce, given its high temperature. They found that their equilibrium calculations yielded a water-depleted mineral atmosphere (i.e., Na, K, Fe, Si, SiO, O, and O 2 as the major atmospheric species).…”

“…However, follow-up secondary eclipse, phase-curve, and transit measurements (Demory et al , 2016a(Demory et al , 2016bRidden-Harper et al 2016;Tsiaras et al 2016), in conjunction with theoretical models (Lammer et al 2013;Ito et al 2015;Kite et al 2016), point to the existence of an envelope.…”

On the ultraviolet anomalies of the WASP-12 and HD 189733 systems: Trojan satellites as a plasma source

“…Rocky Trojans orbiting WASP-12b (equilibrium temperature of about 2578 K, Sing et al 2013) should possess an atmosphere of a different type, dominated by such gases as monatomic Na, O2, monatomic O, SiO, monatomic Mg, and monatomic Fe. This is in agreement with a new study of Ito et al (2015), according to which Na, K, Fe, Si, SiO, O, and O2 are the major atmospheric species outgassed from molten surfaces of rocky Super-Earths.…”

“…None of the studies considering mineral atmospheres of rocky bodies predicts C to be present in large amount Miguel et al 2011;Ito et al 2015). Schaefer & Fegley (2009) investigated the composition of early close-in rocky cores by chemical equilibrium and chemical kinetic calculations.…”