Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD 235088 b (TOI-1430 b) with CARMENES
2023 | journal article. A publication with affiliation to the University of Göttingen.
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Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD 235088 b (TOI-1430 b) with CARMENES
Orell-Miquel, J.; Lampón, M.; López-Puertas, M.; Mallorquín, M.; Murgas, F.; Peláez-Torres, A. & Pallé, E. et al. (2023)
Astronomy and Astrophysics, 677 pp. A56. DOI: https://doi.org/10.1051/0004-6361/202346445
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- Authors
- Orell-Miquel, J.; Lampón, M.; López-Puertas, M.; Mallorquín, M.; Murgas, F.; Peláez-Torres, A.; Pallé, E.; Esparza-Borges, E.; Sanz-Forcada, J.; Tabernero, H. M.; Yan, F.
- Abstract
- HD 235088 (TOI-1430) is a young star known to host a sub-Neptune-sized planet candidate. We validated the planetary nature of HD 235088 b with multiband photometry, refined its planetary parameters, and obtained a new age estimate of the host star, placing it at 600–800 Myr. Previous spectroscopic observations of a single transit detected an excess absorption of He I coincident in time with the planet candidate transit. Here, we confirm the presence of He I in the atmosphere of HD 235088 b with one transit observed with CARMENES. We also detected hints of variability in the strength of the helium signal, with an absorption of −0.91 ± 0.11%, which is slightly deeper (2 σ ) than the previous measurement. Furthermore, we simulated the He I signal with a spherically symmetric 1D hydrodynamic model, finding that the upper atmosphere of HD 235088 b escapes hydrodynamically with a significant mass loss rate of (1.5−5) × 10 10 g s −1 in a relatively cold outflow, with T = 3125 ±375 K, in the photon-limited escape regime. HD 235088 b ( R p = 2.045 ± 0.075 R ⊕ ) is the smallest planet found to date with a solid atmospheric detection – not just of He I but any other atom or molecule. This positions it a benchmark planet for further analyses of evolving young sub-Neptune atmospheres.
- Issue Date
- 2023
- Journal
- Astronomy and Astrophysics
- ISSN
- 0004-6361
- eISSN
- 1432-0746