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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

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 o...

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Main Authors: Orell-Miquel, Jaume (Author) , Lampón, Manuel (Author) , López-Puertas, M. (Author) , Mallorquín, Manuel (Author) , Murgas, F. (Author) , Peláez-Torres, A. (Author) , Pallé, Enric (Author) , Esparza-Borges, Emma (Author) , Sanz-Forcada, J. (Author) , Tabernero, H. M. (Author) , Nortmann, Lisa (Author) , Nagel, E. (Author) , Parviainen, H. (Author) , Zapatero Osorio, Maria Rosa (Author) , Caballero, José A. (Author) , Czesla, S. (Author) , Cifuentes, C. (Author) , Morello, G. (Author) , Quirrenbach, Andreas (Author) , Amado, P. J. (Author) , Fernández-Martín, A. (Author) , Fukui, A. (Author) , Henning, Thomas (Author) , Kawauchi, K. (Author) , Leon, J. P. de (Author) , Molaverdikhani, Karan (Author) , Montes, D. (Author) , Narita, N. (Author) , Reiners, A. (Author) , Ribas, I. (Author) , Sánchez-López, A. (Author) , Schweitzer, A. (Author) , Stangret, M. (Author) , Yan, F. (Author)
Format: Article (Journal)
Language:English
Published: September 2023
In: Astronomy and astrophysics
Year: 2023, Volume: 677, Pages: 1-17
ISSN:1432-0746
DOI:10.1051/0004-6361/202346445
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1051/0004-6361/202346445
Verlag, kostenfrei, Volltext: https://www.aanda.org/articles/aa/abs/2023/09/aa46445-23/aa46445-23.html
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Author Notes:J. Orell-Miquel, M. Lampón, M. López-Puertas, M. Mallorquín, F. Murgas, A. Peláez-Torres, E. Pallé, E. Esparza-Borges, J. Sanz-Forcada, H.M. Tabernero, L. Nortmann, E. Nagel, H. Parviainen, M.R. Zapatero Osorio, J.A. Caballero, S. Czesla, C. Cifuentes, G. Morello, A. Quirrenbach, P.J. Amado, A. Fernández-Martín, A. Fukui, Th. Henning, K. Kawauchi, J.P. de Leon, K. Molaverdikhani, D. Montes, N. Narita, A. Reiners, I. Ribas, A. Sánchez-López, A. Schweitzer, M. Stangret, and F. Yan
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Summary: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<i>σ<i/>) 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<sup>10<sup/> g s<sup>−1<sup/> in a relatively cold outflow, with <i>T<i/> = 3125 ±375 K, in the photon-limited escape regime. HD 235088 b (<i>R<i/><sub>p<sub/> = 2.045 ± 0.075 <i>R<i/><sub>⊕<sub/>) 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.
Item Description:Gesehen am 23.04.2024
Online veröffentlicht: 05. September 2023
Physical Description:Online Resource
ISSN:1432-0746
DOI:10.1051/0004-6361/202346445

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