Identifying interesting planetary systems for future X-ray observations

TL;DR

This paper leverages new and archival X-ray data to identify exoplanets with significant X-ray irradiation, predicting their observability in future X-ray missions and aiding targeted follow-up studies.

Contribution

It introduces a method to estimate exoplanet mass loss rates using X-ray data and models their X-ray transmission spectra for future observatories.

Findings

Identified exoplanets with high X-ray irradiation suitable for follow-up

Estimated mass loss rates for several exoplanets

Predicted X-ray transmission spectra for Hot Jupiters

Abstract

X-ray observations of star-planet systems are important to grow our understanding of exoplanets; these observation allow for studies of photoevaporation of the exoplanetary atmosphere, and in some cases even estimations of the size of the outer planetary atmosphere. The German-Russian eROSITA instrument onboard the SRG (Spectrum Roentgen Gamma) mission is performing the first all-sky X-ray survey since the 1990s, and provides X-ray fluxes and spectra of exoplanet host stars over a much larger volume than was accessible before. Using new eROSITA data as well as archival data from XMM-Newton, Chandra and ROSAT we estimate mass loss rates of exoplanets under an energy-limited escape scenario, and identify several exoplanets with strong X-ray irradiation and expected mass-loss that are amenable to follow-up observations at other wavelengths. We model sample spectra using a toy model of an exoplanetary atmosphere to predict what exoplanet transit observations with future X-ray missions such as Athena will look like, and estimate the observable X-ray transmission spectrum for a typical Hot Jupiter-type exoplanet.