Binned Kepler photometry (blue dots) of the KOI population which both exists above the period-radius valley and below the H2 atmospheric evaporation limit shown in Figure 4. Overlaid is a clear H2 atmosphere (µ = 2 g/mol) refraction model (solid red line). Despite these exoplanets being the only ones in the APRV population capable of holding H/He atmospheres, any possible refraction effects are severely dampened when compared to the simulated effect for an optically thin H/He atmosphere. — astro-ph.EP
We present an analysis on the detection viability of refraction effects in Kepler’s exoplanet atmospheres using binning techniques for their light curves in order to compare against simulated refraction effects.
We split the Kepler exoplanets into sub-populations according to orbital period and planetary radius, then search for out-of-transit changes in the relative flux associated with atmospheric refraction of starlight. The presence of refraction effects – or lack thereof – may be used to measure and set limits on the bulk properties of an atmosphere, including mean molecular weight or the presence of hazes.
In this work, we use the presence of refraction effects to test whether exoplanets above the period-radius valley have H/He atmospheres, which high levels of stellar radiation could evaporate away, in turn leaving rocky cores below the valley.
We find strong observational evidence of refraction effects for exoplanets above the period-radius valley based on Kepler photometry, however those related to optically thin H/He atmospheres are not common in the observed planetary population.
This result may be attributed to signal dampening caused by clouds and hazes, consistent with the optically thick and intrinsically hotter atmospheres of Kepler exoplanets caused by relatively close host star proximity.
Dereck-Alexandre Lizotte, Jason Rowe, James Sikora, Michael R. B. Matesic
Comments: 13 pages, 13 figures, to be submitted in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2507.02126 [astro-ph.EP] (or arXiv:2507.02126v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2507.02126
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Submission history
From: Dereck-Alexandre Lizotte
[v1] Wed, 2 Jul 2025 20:20:24 UTC (384 KB)
https://arxiv.org/abs/2507.02126
Astrobiology
