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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2511.04372 |
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| _version_ | 1866912691319209984 |
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| author | Duann, Y. Lai, S. -H. Hoeijmakers, H. J. Johansen, A. Lin, C. -L. Huang, L. -C. Chang, Y. -Y. Sreejith, A. G. France, K. Chang, L. C. Ip, W. -H. |
| author_facet | Duann, Y. Lai, S. -H. Hoeijmakers, H. J. Johansen, A. Lin, C. -L. Huang, L. -C. Chang, Y. -Y. Sreejith, A. G. France, K. Chang, L. C. Ip, W. -H. |
| contents | Ultra-hot Jupiters (UHJs) in close orbits around early-type stars provide natural laboratories for studying atmospheric escape and star-planet interactions under extreme irradiation and wind conditions. The near-ultraviolet (NUV) regime is particularly sensitive to extended upper atmospheric and magnetospheric structures. We investigate whether star-planet interactions in the WASP-189 system could plausibly account for the early ingress feature suggested by NUV transit fitting models. We analyzed three NUV transits of WASP-189b observed as part of the Colorado Ultraviolet Transit Experiment (CUTE), which employs a 6U CubeSat dedicated to exoplanet spectroscopy. To explore whether the observed transit asymmetry could plausibly arise from a magnetospheric bow shock (MBS), we performed magnetohydrodynamic (MHD) simulations using representative stellar wind velocities and planetary atmospheric densities. During Visit 3, we identified an approximately 31.5-minute phase offset that is consistent with an early ingress. Our MHD simulations indicate that with a wind speed of 573 km s-1 and an upper atmospheric density of about 4.6e-11 kg m-3, a higher-density zone due to compression can form ahead of the planet within five planetary radii where the fast-mode Mach number falls below ~0.56, even without a MBS. Shock cooling and crossing time estimates suggest that such a pileup could produce detectable NUV absorption. Our results indicate that while MBS formation is feasible for WASP-189b, low stellar-wind speeds favor NUV-detectable magnetic pileups over classical bow shocks and enhance the potential detectability of early-ingress signatures. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_04372 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Magnetohydrodynamic simulation assessment of a potential near-ultraviolet early ingress in WASP-189b Duann, Y. Lai, S. -H. Hoeijmakers, H. J. Johansen, A. Lin, C. -L. Huang, L. -C. Chang, Y. -Y. Sreejith, A. G. France, K. Chang, L. C. Ip, W. -H. Earth and Planetary Astrophysics Ultra-hot Jupiters (UHJs) in close orbits around early-type stars provide natural laboratories for studying atmospheric escape and star-planet interactions under extreme irradiation and wind conditions. The near-ultraviolet (NUV) regime is particularly sensitive to extended upper atmospheric and magnetospheric structures. We investigate whether star-planet interactions in the WASP-189 system could plausibly account for the early ingress feature suggested by NUV transit fitting models. We analyzed three NUV transits of WASP-189b observed as part of the Colorado Ultraviolet Transit Experiment (CUTE), which employs a 6U CubeSat dedicated to exoplanet spectroscopy. To explore whether the observed transit asymmetry could plausibly arise from a magnetospheric bow shock (MBS), we performed magnetohydrodynamic (MHD) simulations using representative stellar wind velocities and planetary atmospheric densities. During Visit 3, we identified an approximately 31.5-minute phase offset that is consistent with an early ingress. Our MHD simulations indicate that with a wind speed of 573 km s-1 and an upper atmospheric density of about 4.6e-11 kg m-3, a higher-density zone due to compression can form ahead of the planet within five planetary radii where the fast-mode Mach number falls below ~0.56, even without a MBS. Shock cooling and crossing time estimates suggest that such a pileup could produce detectable NUV absorption. Our results indicate that while MBS formation is feasible for WASP-189b, low stellar-wind speeds favor NUV-detectable magnetic pileups over classical bow shocks and enhance the potential detectability of early-ingress signatures. |
| title | Magnetohydrodynamic simulation assessment of a potential near-ultraviolet early ingress in WASP-189b |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2511.04372 |