![Representative spectral energy distribution fits for four HWO ExEP target stars: HD 2151 (upper left), HD 3651 A (upper right), HD 4813 (lower left), and HD 10700 (lower right). In each panel, the solid curve represents the best-fitting Pickles (1998) template spectrum, and the filled circles show the broadband photometry with associated uncertainties. Photometric error bars are shown in the y-direction, and filter widths in the x-direction. Fractional residuals between the template flux averaged over each bandpass and the literature photometry are shown in the lower sub-panels. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Spectral-Energy.png?fit=1200%2C672&ssl=1)
[astro-ph.EP] The Habitable Worlds Observatory (HWO) will directly image and characterize planets potentially similar to Earth orbiting nearby stars.
Accurate stellar properties, particularly effective temperatures (Teff), angular diameters (θ⋆), and bolometric fluxes (Fbol), are essential for reliable Habitable Zone (HZ) calculations, exoplanet yield predictions, and coronagraph design trade studies.
We present a spectral energy distribution (SED) analysis for the 164 stars from the HWO Exoplanet Exploration Program (ExEP) list, using χ2-minimization fits of empirical spectral templates from the Pickles stellar spectral flux library to broadband photometric data.
The SED fits provide direct measurements of Fbol. We adopt spectroscopic Teff values from the PASTEL catalog for 127 of the 164 stars, with the remainder drawn from the HWO ExEP catalog, and use these in combination with Fbol to calculate θ⋆ via the Stefan-Boltzmann equation.
As a consistency check, we compare the Pickles template Teff with the adopted spectroscopic values and find agreement to within ∼3% for 65% of the sample, with a systematic tendency for the templates to yield cooler values.
We identify 48 stars with discrepancies exceeding 200~K, including close binary systems where photometric contamination compromises the SED solution.
We discuss the implications for HZ boundary calculations, atmospheric retrieval of directly imaged planets, and target prioritization for HWO. This SED catalog constitutes a uniform set of empirically determined Fbol values and associated stellar parameters for the HWO target sample.
Stephen R. Kane, Kaspar von Braun, Tara Fetherolf, Natalie R. Hinkel
Comments: 14 pages, 2 figures, 1 table, accepted for publication in PASP
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2608.11333 [astro-ph.EP] (or arXiv:2608.11333v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2608.11333
Focus to learn more
Submission history
From: Stephen Kane
[v1] Tue, 11 Aug 2026 18:38:14 UTC (174 KB)
https://arxiv.org/abs/2608.11333
Astrobiology, Astrochemistry, exoplanet,
