Modeling Atmospheric Ion Escape from Kepler-1649 b and c over Time
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| Main Authors: | , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Li, Haitao Dong, Chuanfei Xie, Lianghai He, Xinyi Chin, Laura Wang, Xinke Yan, Hong-Liang Qin, Jinxiao Mayne, Nathan Mak, Mei Ting Georgakarakos, Nikolaos Christie, Duncan Zhu, Yajun Rong, Zhaojin Ma, Jinlian Li, Xiaobo Chen, Shi Zhou, Hai |
| author_facet | Li, Haitao Dong, Chuanfei Xie, Lianghai He, Xinyi Chin, Laura Wang, Xinke Yan, Hong-Liang Qin, Jinxiao Mayne, Nathan Mak, Mei Ting Georgakarakos, Nikolaos Christie, Duncan Zhu, Yajun Rong, Zhaojin Ma, Jinlian Li, Xiaobo Chen, Shi Zhou, Hai |
| contents | Rocky planets orbiting M-dwarf stars are prime targets for atmospheric characterization, yet their long-term evolution under intense stellar winds and high-energy radiation remains poorly constrained. The Kepler-1649 system, hosting two terrestrial exoplanets orbiting an M5V star, provides a valuable laboratory for studying atmospheric evolution in the extreme environments typical of M-dwarf systems. In this Letter we show that both planets could have retained atmospheres over gigayear timescales. Using a multi-species magnetohydrodynamic model, we simulate atmospheric ion escape driven by stellar winds and extreme ultraviolet radiation from 0.8 to 4.0 Gyr. The results reveal a clear decline in total ion escape rates with stellar age, as captured by a nonparametric LOWESS regression, with O$^{+}$ comprising 98.3%-99.9% of the total loss. Escape rates at 4.0 Gyr are two to three orders of magnitude lower than during early epochs. At 0.8 Gyr, planet b exhibits 3.79$\times$ higher O$^{+}$ escape rates than planet c, whereas by 4.0 Gyr its O$^{+}$ escape rate becomes 39.5$\times$ lower. This reversal arises from a transition to sub-magnetosonic star-planet interactions, where the fast magnetosonic Mach number, $M_f$, falls below unity. Despite substantial early atmospheric erosion, both planets may have retained significant atmospheres, suggesting potential long-term habitability. These findings offer predictive insight into atmospheric retention in the Kepler-1649 system and inform future JWST observations of similar M-dwarf terrestrial exoplanets aimed at refining habitability assessments. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2504_12541 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Modeling Atmospheric Ion Escape from Kepler-1649 b and c over Time Li, Haitao Dong, Chuanfei Xie, Lianghai He, Xinyi Chin, Laura Wang, Xinke Yan, Hong-Liang Qin, Jinxiao Mayne, Nathan Mak, Mei Ting Georgakarakos, Nikolaos Christie, Duncan Zhu, Yajun Rong, Zhaojin Ma, Jinlian Li, Xiaobo Chen, Shi Zhou, Hai Earth and Planetary Astrophysics Rocky planets orbiting M-dwarf stars are prime targets for atmospheric characterization, yet their long-term evolution under intense stellar winds and high-energy radiation remains poorly constrained. The Kepler-1649 system, hosting two terrestrial exoplanets orbiting an M5V star, provides a valuable laboratory for studying atmospheric evolution in the extreme environments typical of M-dwarf systems. In this Letter we show that both planets could have retained atmospheres over gigayear timescales. Using a multi-species magnetohydrodynamic model, we simulate atmospheric ion escape driven by stellar winds and extreme ultraviolet radiation from 0.8 to 4.0 Gyr. The results reveal a clear decline in total ion escape rates with stellar age, as captured by a nonparametric LOWESS regression, with O$^{+}$ comprising 98.3%-99.9% of the total loss. Escape rates at 4.0 Gyr are two to three orders of magnitude lower than during early epochs. At 0.8 Gyr, planet b exhibits 3.79$\times$ higher O$^{+}$ escape rates than planet c, whereas by 4.0 Gyr its O$^{+}$ escape rate becomes 39.5$\times$ lower. This reversal arises from a transition to sub-magnetosonic star-planet interactions, where the fast magnetosonic Mach number, $M_f$, falls below unity. Despite substantial early atmospheric erosion, both planets may have retained significant atmospheres, suggesting potential long-term habitability. These findings offer predictive insight into atmospheric retention in the Kepler-1649 system and inform future JWST observations of similar M-dwarf terrestrial exoplanets aimed at refining habitability assessments. |
| title | Modeling Atmospheric Ion Escape from Kepler-1649 b and c over Time |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2504.12541 |