The MUSCLES Extension for Atmospheric Transmission Spectroscopy: Spectral energy distributions for 20 exoplanet host stars that JWST observed in Cycle 1

TL;DR

This paper provides detailed spectral energy distributions for 20 exoplanet host stars observed by JWST, crucial for interpreting exoplanet atmospheres, and highlights the high ultraviolet fluxes that could influence atmospheric escape.

Contribution

It introduces comprehensive SEDs for 20 JWST-observed stars, combining new and archival data, and assesses their implications for exoplanet atmospheric studies.

Findings

Most target planets receive stronger UV fluxes than Earth.

High UV fluxes suggest potential for atmospheric escape.

Constructed SEDs for key target stars and proxies.

Abstract

Correctly interpreting JWST spectra of close-in exoplanets requires a measurement of the X-ray and ultraviolet light that the planets receive from their host stars. Here we provide spectral energy distributions (SEDs) covering the range $\approx5-1\times10^7$A for 20 transiting exoplanet host stars observed in JWST Cycle 1. The SEDs are constructed out of new and archival Hubble Space Telescope, Chandra X-ray Observatory and/or XMM-Newton data combined with spectra from models or stars with similar properties (proxies) filling in unobserved gaps. We have also constructed SEDs of likely Habitable Worlds Observatory targets $\kappa^1$ Ceti, $\tau$ Ceti, $\epsilon$ Indi and 70 Oph B for use as proxies. We find that the JWST target planets almost all experience much stronger ultraviolet fluxes than the Earth, especially in the extreme ultraviolet, even for planets with similar overall instellation. Strong ongoing or past atmospheric escape is possible for a majority of these planets. We also assess the now considerable sample of panchromatic stellar SEDs and its applicability for current JWST observations and beyond.