The Radiation Environments of Middle-Aged F-Type Stars

TL;DR

This study presents the first comprehensive spectral energy distribution of a mid-F star, Procyon A, combining observational data and models to assess exoplanet atmospheric effects and transit detectability.

Contribution

It provides the first simultaneous FUV spectral observations of a cool star and develops a detailed SED for a mid-F star, supporting exoplanet atmospheric and transit studies.

Findings

Developed the first SED of a mid-F star by combining observations and models.

Simulated exoplanet atmospheric response indicating minimal atmospheric escape.

Predicted Lyα transit signals detectable with future telescopes up to 150 pc away.

Abstract

Far ultraviolet (FUV) emission lines from dwarf stars are important driving sources of photochemistry in planetary atmospheres. Properly interpreting spectral features of planetary atmospheres critically depends on the emission of its host star. While the spectral energy distributions (SEDs) of K- and M-type stars have been extensively characterized by previous observational programs, the full X-ray to infrared SED of F-type stars has not been assembled to support atmospheric modeling. On the second flight of the Suborbital Imaging Spectrograph for Transition-region Irradiance from Nearby Exoplanet host stars (SISTINE-2) rocket-borne spectrograph, we successfully captured the FUV spectrum of Procyon A (F5 IV-V) and made the first simultaneous observation of several emission features across the FUV bandpass (1010 - 1270 and 1300 - 1565 \r{A}) of any cool star. We combine flight data with stellar models and archival observations to develop the first SED of a mid-F star. We model the response of a modern Earth-like exoplanet's upper atmosphere to the heightened X-ray and extreme ultraviolet radiation within the habitable zone of Procyon A. These models indicate that this planet would not experience significant atmospheric escape. We simulate observations of the Ly$\alpha$ transit signal of this exoplanet with the Hubble Space Telescope (HST) and the Habitable Worlds Observatory (HWO). While marginally detectable with HST, we find that H I Ly$\alpha$ transits of potentially habitable exoplanets orbiting high radial velocity F-type stars could be observed with HWO for targets up to 150 pc away.