Observational Signatures Of Circumstellar Gas Tori Formed by Planetary Mass-Loss from Close-In Exoplanets

Close-in exoplanets with H/He atmospheres often undergo hydrodynamic escape. In extreme cases, it is hypothesized that the mass loss can be high enough for the escaping planetary material to wrap around the star, forming a long-lasting circumstellar torus.

In this work, we develop a physical model of such circumstellar tori and use a ray tracing scheme to calculate the attenuation of stellar light passing through them. We show that the presence of a circumstellar torus significantly increases the equivalent width of the observed stellar He I 10830~Å~line.

When combined with observations of the star’s Ca II H & K lines, these systems can typically be distinguished from field stars. Based on these results, we propose a survey of stars hosting close-in planets, combining observations of the He I 10830~Å~and Ca II H & K lines to search for circumstellar tori generated from planetary mass-loss in these systems.

Ethan Schreyer, Ruth Murray-Clay

Comments: Accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2602.16816 [astro-ph.EP] (or arXiv:2602.16816v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2602.16816
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Submission history
From: Ethan Schreyer Mr
[v1] Wed, 18 Feb 2026 19:25:24 UTC (2,124 KB)
https://arxiv.org/abs/2602.16816
Astrobiology,