Cold Day-side Winds Shape Large Leading Streams in Evaporating Exoplanet Atmospheres
Recent observations of planetary atmospheres in HAT-P-32 b and HAT-P-67 b reveal extensive outflows reaching up to hundreds of planetary radii. The helium 1083 nm light curves for these planets, captured across their full orbits, show notable asymmetries: both planets display more pronounced pre-transit than post-transit absorptions, with HAT-P-67 b being the more extreme case of that geometry.
Using three-dimensional (3D) hydrodynamic simulations, we identify key factors influencing the formation of a dense leading outflow stream and characterize its morphology. Our models suggest that such a geometry of escaped material is caused by a relatively cold outflow of high mass-loss rate, launched preferentially from the planet’s day side. From the simulations we calculate synthetic He I 1083 nm spectra that show large absorption depths and irregular line profiles due to complex gas kinematics.
We find that the measurements of the He I 1083 nm equivalent width and the velocity shift relative to the planet’s rest frame, observed over a significant portion of the planet’s orbital phase, can provide important constraints on the outflow properties and its interaction with the stellar wind.
F. Nail, M. MacLeod, A. Oklopčić, M. Gully-Santiago, C.V. Morley, Z. Zhang
Comments: 10 pages, 6 figures, https://doi.org/10.5281/zenodo.13988501
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2410.19381 [astro-ph.EP] (or arXiv:2410.19381v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.19381
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Submission history
From: Fabienne Nail
[v1] Fri, 25 Oct 2024 08:32:20 UTC (4,608 KB)
https://arxiv.org/abs/2410.19381
Astrobiology,