Hot super-Earths stripped by their host stars

TL;DR

This study uses asteroseismology to confirm a predicted 'hot super-Earth desert' caused by photo-evaporation, showing a lack of close-in super-Earths with high incident flux, supporting theoretical models.

Contribution

It provides observational evidence for the hot super-Earth desert caused by photo-evaporation, confirming a key prediction of planetary evolution theories.

Findings

No super-Earths with radii 2.2-3.8 Earth radii at high incident flux

Presence of super-Earths at low incident flux

Supports evaporation models predicting a dearth of close-in super-Earths

Abstract

Simulations predict that hot super-Earth sized exoplanets can have their envelopes stripped by photo-evaporation, which would present itself as a lack of these exoplanets. However, this absence in the exoplanet population has escaped a firm detection. Here we demonstrate, using asteroseismology on a sample of exoplanets and exoplanet candidates observed during the Kepler mission that, while there is an abundance of super-Earth sized exoplanets with low incident fluxes, none are found with high incident fluxes. We do not find any exoplanets with radii between 2.2 and 3.8 Earth radii with incident flux above 650 times the incident flux on Earth. This gap in the population of exoplanets is explained by evaporation of volatile elements and thus supports the predictions. The confirmation of a hot-super-Earth desert caused by evaporation will add an important constraint on simulations of planetary systems, since they must be able to reproduce the dearth of close-in super-Earths.