The MUSCLES Extension for Atmospheric Transmission Spectroscopy: Spectral energy distributions For 20 Exoplanet Host Stars That JWST Observed in Cycle 1

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 ≈5−1×10⁷A 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 κ1 Ceti, τ Ceti, ϵ 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.

David J. Wilson, Allison Youngblood, Girish M. Duvvuri, Kevin France, P. Christian Schneider, Alexander Brown, Isabella Longo, Cynthia S. Froning, Jacob L. Bean, J. Sebastian Pineda, Eliza M.-R. Kempton, Yamila Miguel, Thomas M. Evans-Soma, Zachory Berta-Thompson

Comments: Accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2601.01628 [astro-ph.EP] (or arXiv:2601.01628v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2601.01628
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From: David Wilson
[v1] Sun, 4 Jan 2026 18:20:12 UTC (5,073 KB)
https://arxiv.org/abs/2601.01628
Astrobiology,