Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD 235088 b (TOI-1430 b) with CARMENES
Journal article, 2023
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 (2γ) 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) × 1010 g s-1 in a relatively cold outflow, with T = 3125 ±375 K, in the photon-limited escape regime. HD 235088 b (Rp = 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.
Planets and satellites: individual: HD 235088 b
Planets and satellites: atmospheres
Techniques: spectroscopic
Stars: individual: HD 235088
Techniques: photometric
Author
J. Orell-Miquel
University of La Laguna
Instituto de Astrofísica de Canarias
M. Lampon
Spanish National Research Council (CSIC)
M. López-Puertas
Spanish National Research Council (CSIC)
M. Mallorquín
University of La Laguna
Instituto de Astrofísica de Canarias
F. Murgas
Instituto de Astrofísica de Canarias
University of La Laguna
A. Peláez-Torres
Instituto de Astrofísica de Canarias
University of La Laguna
Enric Palle
Instituto de Astrofísica de Canarias
University of La Laguna
E. Esparza-Borges
Instituto de Astrofísica de Canarias
University of La Laguna
J. Sanz-Forcada
European Space Astronomy Centre (ESAC)
H. M. Tabernero
Centro de Astrobiologia (CAB)
L. Nortmann
University of Göttingen
E. Nagel
University of Göttingen
H. Parviainen
University of La Laguna
Instituto de Astrofísica de Canarias
M. Zapatero-Osorio
Centro de Astrobiologia (CAB)
J. A. Caballero
Centro de Astrobiologia (CAB)
S. Czesla
Thüringer Landessternwarte Tautenburg
C. Cifuentes
Centro de Astrobiologia (CAB)
Giuseppe Morello
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Instituto de Astrofísica de Canarias
A. Quirrenbach
Heidelberg-Königstuhl State Observatory
P. J. Amado
Spanish National Research Council (CSIC)
A. Fernández-Martín
Calar Alto Astronomical Observatory
A. Fukui
National Institutes of Natural Sciences
Instituto de Astrofísica de Canarias
T. Henning
Max Planck Society
Kiyoe Kawauchi
University of Tokyo
Jerome P. De Leon
University of Tokyo
K. Molaverdikhani
Ludwig Maximilian University of Munich (LMU)
Heidelberg-Königstuhl State Observatory
D. Montes
IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos)
Norio Narita
National Institutes of Natural Sciences
Instituto de Astrofísica de Canarias
University of Tokyo
A. Reiners
University of Göttingen
I. Ribas
Spanish National Research Council (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
A. Sánchez-López
Spanish National Research Council (CSIC)
A. Schweitzer
University of Hamburg
M. Stangret
Istituto nazionale di astrofisica (INAF)
F. Yan
University of Science and Technology of China
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 677 A56Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
DOI
10.1051/0004-6361/202346445