![Cumulative oxygen loss for planets at the habitable zone of each sample star over 1 Gyr, assuming constant stellar XUV flux at the HZ and no replenishment of oxygen. The curves are calculated using the energy-limited O2 loss prescription from V. S. Airapetian et al. 2017. Colored lines show individual stars, with solid segments representing the earliest ages (for stars with age ranges) and dashed segments extending beyond the minimum age. The black solid line shows the solar reference. Horizontal lines indicate the present-day Earth atmospheric O2 content (∼0.2 bars; dotted) and the total mass of Earth’s oceans (∼240 bars; dashed), providing reference levels for planetary habitability. -- [astro-ph.SR]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Panchromatic.png?fit=1200%2C679&ssl=1)
[astro-ph.SR] Characterizing the high-energy radiation environments of stars plays a critical role in determining which systems’ planets are capable of retaining atmospheres and sustaining habitable conditions.
X-ray through ultraviolet (UV) radiation drives atmospheric photochemistry, heating, and escape, making accurate characterization of stellar high-energy emission essential for both interpreting future exoplanet observations and identifying the most promising targets for life detection.
We construct panchromatic spectral energy distributions (SEDs) spanning the X-ray through radio for 12 nearby low-mass and Sun-like stars with directly imageable habitable zones that are prioritized targets for the Habitable Worlds Observatory (HWO) and Extremely Large Telescopes (ELTs).
These SEDs are generated using forward stellar atmosphere models guided and constrained by available archival X-ray and UV observations. We find that many stars in this sample exhibit elevated high-energy radiation environments relative to the modern Sun, with habitable zone X-ray and extreme UV (XUV) fluxes frequently exceeding solar values by 1-2 orders of magnitude.
The elevated emission likely reflects a combination of sample selection effects, differences in stellar age and rotation, and intrinsic magnetic variability, with multi-epoch observations demonstrating that variability alone can significantly alter inferred radiation environments.
These results highlight high-energy radiation as an important discriminator in identifying the most promising habitable planet hosts and demonstrate the need for expanded X-ray and UV observations to complete the stellar characterization necessary for HWO target prioritization.
Sarah Peacock, Breanna A. Binder, Edward W. Schwieterman, Margaret C. Turnbull, Stephen R. Kane, Katherine Garcia-Sage, Alison Farrish
Comments: 29 pages, 8 Figures, 7 Tables, accepted to ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2608.27344 [astro-ph.SR] (or arXiv:2608.27344v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2608.27344
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Submission history
From: Sarah Peacock
[v1] Thu, 27 Aug 2026 16:45:35 UTC (3,121 KB)
https://arxiv.org/abs/2608.27344
Astrobiology
