Issue |
A&A
Volume 685, May 2024
|
|
---|---|---|
Article Number | A147 | |
Number of page(s) | 20 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202349133 | |
Published online | 22 May 2024 |
TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization
1
Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, 10125 Torino, Italy
2
Thüringer Landessternwarte Tautenburg, 07778 Tautenburg, Germany
e-mail: elisa@tls-tautenburg.de
3
Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
4
Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
5
Department of Space, Earth and Environment, Chalmers University of Technology, 412 96 Gothenburg, Sweden
6
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
7
Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
8
INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
9
Centro de Astrobiología, (CSIC-INTA), ESAC Campus, Camino bajo del castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
10
Steward Observatory and Department of Astronomy, The University of Arizona, Tucson, AZ 85721, USA
11
Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
12
Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
13
Max Planck Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
14
Departamento de Física de la Tierra y Astrofísica and IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
15
Department of Physics, Ariel University, Ariel 40700, Israel
16
Vereniging Voor Sterrenkunde, Oude Bleken 12, 2400 Mol, Belgium
17
AstroLAB IRIS, Provinciaal Domein “De Palingbeek”, Verbrande-molenstraat 5, 8902 Zillebeke, Ieper, Belgium
18
Komaba Institute for Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
19
Department of Multi-Disciplinary Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
20
Institut d’Estudis Espacials de Catalunya (IEEC), Calle Gran Capita 2–4, 08034 Barcelona, Spain
21
Astrobiology Center, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
22
Centre for Mathematical Plasma-Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium
23
Centro Astronómico Hispano en Andalucía (CAHA), Observatorio de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Spain
24
Institut für Astrophysik und Geophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
25
Department of Astronomy & Astrophysics, University of Chicago, Chicago, IL 60637, USA
26
Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
27
Institut de Ciéncies de l'Espai (CSIC-IEEC), Campus UAB, de Can Magrans s/n, 08193 Bellaterra, Barcelona, Spain
28
Centro de Astrobiología (CSIC-INTA), Carretera de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
29
Center for Astroparticles and High Energy Physics (CAPA), Universidad de Zaragoza, 50009 Zaragoza, Spain
30
School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
Received:
29
December
2023
Accepted:
4
March
2024
We report the confirmation and mass determination of a mini-Neptune transiting the M3.5 V star TOI-4438 (G 182-34) every 7.44 days. A transit signal was detected with NASA’s TESS space mission in the sectors 40, 52, and 53. In order to validate the planet TOI-4438 b and to determine the system properties, we combined TESS data with high-precision radial velocity measurements from the CARMENES spectrograph, spanning almost one year, and ground-based transit photometry. We found that TOI-4438 b has a radius of Rb = 2.52 ± 0.13 R⊕ (5% precision), which together with a mass of Mb = 5.4 ± 1.1 M⊕ (20% precision), results in a bulk density of ρb = 1.85−0.44+0.51 g cm−3 (~28% precision), aligning the discovery with a volatile-rich planet. Our interior structure retrieval with a pure water envelope yields aminimum water mass fraction of 46% (1σ). TOI-4438 b is a volatile-rich mini-Neptune with likely H/He mixed with molecules, such as water, CO2, and CH4. The primary star has a J-band magnitude of 9.7, and the planet has a high transmission spectroscopy metric (TSM) of 136 ± 13. Taking into account the relatively warm equilibrium temperature of Teq = 435 ± 15 K, and the low activity level of its host star, TOI-4438 b is one of the most promising mini-Neptunes around an M dwarf for transmission spectroscopy studies.
Key words: techniques: photometric / techniques: radial velocities / planets and satellites: composition / planets and satellites: detection
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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