# EUV influences on exoplanet atmospheric stability and evolution

## TL;DR

This paper emphasizes the importance of stellar EUV radiation in determining exoplanet atmospheric stability and evolution, highlighting the limitations of current observations and models for characterizing EUV spectra.

## Contribution

It underscores the need for dedicated EUV observations and discusses the challenges in accurately modeling EUV spectra of exoplanet host stars.

## Key findings

- EUV drives atmospheric mass loss in exoplanets.
- Current data and models are insufficient for low-mass star EUV spectra.
- Dedicated EUV observatories are necessary for better characterization.

## Abstract

The planetary effective surface temperature alone is insufficient to characterize exoplanet atmospheres and their stability or evolution. Considering the star-planet system as a whole is necessary, and a critical component of the system is the photoionizing stellar extreme ultraviolet emission (EUV; 100-912 {\AA}). EUV photons drive atmospheric mass loss through thermal and nonthermal processes, and an accurate accounting of the EUV energy deposition in a planet's energy budget is essential, especially for terrestrial habitable zone planets and close-in gaseous planets. Direct EUV observations of exoplanet host stars would require a new, dedicated observatory. Archival observations from the $\textit{EUVE}$ satellite, models, and theory alone are insufficient to accurately characterize EUV spectra of the majority of exoplanet host stars, especially for low-mass stars.