Upper panels: Equatorial rotational velocity (v eq ) vs. projected rotational velocity (v sin i) for stars in Tiers 1, 2, and 3.
The v sin i values are taken directly from the ARC and the v eq values are calculated using P rot from the ARC and R⋆ from the HPIC.
We describe our data collection strategy, provide an overview of currently known activity and rotation properties in the Activity and Rotation Catalog (ARC) for potential HWO target stars, and briefly review known relationships between stellar inclination, rotation, activity, and age.
However, stellar activity is temporal in nature, such that activity properties should be regularly monitored in order to remain up-to-date for informing future observations.
In particular, we find that stellar activity cycles are measured for fewer than 20% of high interest potential HWO target stars.
Upper panels: Equatorial rotational velocity (v eq ) vs. projected rotational velocity (v sin i) for stars in Tiers 1, 2, and 3. The v sin i values are taken directly from the ARC and the v eq values are calculated using P rot from the ARC and R⋆ from the HPIC. Several stars in each tier fall in a region of parameter space that is mathematically forbidden, i.e., requiring sin i > 1. Lower Panels: Expected and observed inclination distributions for stars in Tiers 1, 2, and 3. The observed distributions are systematically distinct from the expected distributions. Not only do they predict undefined stellar inclinations, but the results favor face-on orbits (i = 0◦ ) rather than edge-on orbits (i = 90◦) as one would expect if stellar spin axes were drawn from an isotropic distribution. — astro-ph.SR
A major goal of the Habitable Worlds Observatory (HWO) is to precisely characterize exoplanets and their atmospheres.
However, magnetic activity from an exoplanet‘s host star can complicate measurements of both the stellar and planetary properties, and stellar activity can be an important factor in our interpretation of the evolutionary history of an exoplanet. In this work, we assess the extent to which magnetic activity has been characterized for potential HWO target stars by collating archival measurements of relevant observables as published in a broad range of photometric and spectroscopic datasets.
We describe our data collection strategy, provide an overview of currently known activity and rotation properties in the Activity and Rotation Catalog (ARC) for potential HWO target stars, and briefly review known relationships between stellar inclination, rotation, activity, and age.
Overall, we find that stellar activity (S-index and R’HK) and rotation (v sin i and Prot) properties have been measured for at least 70% systems that are currently of high interest as potential HWO atmospheric characterization targets. However, stellar activity is temporal in nature, such that activity properties should be regularly monitored in order to remain up-to-date for informing future observations.
In particular, we find that stellar activity cycles are measured for fewer than 20% of high interest potential HWO target stars. Measuring a star’s activity cycle is critical for anticipating times when higher levels of magnetic activity may occur during planned HWO observations, which may interfere with measuring precise exoplanet atmospheric characteristics.
Tara Fetherolf, Arvind F. Gupta, Elisabeth R. Newton, Andrea P. Buccino, Jennifer A. Burt, Jose A. Caballero, Sebastian Carrazco-Gaxiola, Mariela C. Vieytes, Natalie R. Hinkel, Eric E. Mamajek
Comments: 28 pages, 11 figures, submitted to PASP, catalog available: this https URL
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2605.22618 [astro-ph.SR](or arXiv:2605.22618v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2605.22618
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Submission history
From: Tara Fetherolf
[v1] Thu, 21 May 2026 15:30:38 UTC (1,679 KB)
https://arxiv.org/abs/2605.22618
Astrobiology, Exoplanet, Astronomy,
