Cold day-side winds shape large leading streams in evaporating exoplanet atmospheres
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910963681198080 |
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| author | Nail, F. MacLeod, M. Oklopčić, A. Gully-Santiago, M. Morley, C. V. Zhang, Z. |
| author_facet | Nail, F. MacLeod, M. Oklopčić, A. Gully-Santiago, M. Morley, C. V. Zhang, Z. |
| contents | 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_19381 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Cold day-side winds shape large leading streams in evaporating exoplanet atmospheres Nail, F. MacLeod, M. Oklopčić, A. Gully-Santiago, M. Morley, C. V. Zhang, Z. Earth and Planetary Astrophysics 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. |
| title | Cold day-side winds shape large leading streams in evaporating exoplanet atmospheres |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2410.19381 |