TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization
Journal article, 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.

Planets and satellites: detection

Techniques: radial velocities

Techniques: photometric

Planets and satellites: composition

Author

E. Goffo

University of Turin

Thüringer Landessternwarte Tautenburg

Priyanka Chaturvedi

Thüringer Landessternwarte Tautenburg

F. Murgas

University of La Laguna

Instituto de Astrofísica de Canarias

Giuseppe Morello

Instituto de Astrofísica de Canarias

Spanish National Research Council (CSIC)

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

J. Orell-Miquel

Instituto de Astrofísica de Canarias

University of La Laguna

L. Acuña

Max Planck Society

L. Peña-Moñino

Spanish National Research Council (CSIC)

Enric Palle

University of La Laguna

Instituto de Astrofísica de Canarias

A. Hatzes

Thüringer Landessternwarte Tautenburg

S. Geraldía-González

University of La Laguna

Instituto de Astrofísica de Canarias

Francisco J. Pozuelos

Spanish National Research Council (CSIC)

A. F. Lanza

Istituto nazionale di astrofisica (INAF)

D. Gandolfi

University of Turin

J. A. Caballero

Centro de Astrobiologia (CAB)

M. Schlecker

University of Arizona

M.A. Pérez-Torres

Spanish National Research Council (CSIC)

University of Zaragoza

European University Cyprus

N. Lodieu

University of La Laguna

Instituto de Astrofísica de Canarias

A. Schweitzer

University of Hamburg

Coel Hellier

Keele University

S. V. Jeffers

Max Planck Society

C. Duque-Arribas

IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos)

C. Cifuentes

Centro de Astrobiologia (CAB)

V. J. S. Bejar

University of La Laguna

Instituto de Astrofísica de Canarias

M. Daspute

Ariel University

F. Dubois

IRIS

Vereniging Voor Sterrenkunde (VVS)

S. Dufoer

Vereniging Voor Sterrenkunde (VVS)

E. Esparza-Borges

University of La Laguna

Instituto de Astrofísica de Canarias

A. Fukui

Instituto de Astrofísica de Canarias

University of Tokyo

Y. Hayashi

University of Tokyo

Enrique Herrero

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

M. Mori

University of Tokyo

Norio Narita

Instituto de Astrofísica de Canarias

University of Tokyo

National Institutes of Natural Sciences

H. Parviainen

University of La Laguna

Instituto de Astrofísica de Canarias

L. Tal-Or

Ariel University

S. Vanaverbeke

Vereniging Voor Sterrenkunde (VVS)

IRIS

KU Leuven

I. Hermelo

Calar Alto Astronomical Observatory

P. J. Amado

Spanish National Research Council (CSIC)

S. Dreizler

University of Göttingen

T. Henning

Max Planck Society

J. Lillo-Box

Centro de Astrobiologia (CAB)

R. Luque

Spanish National Research Council (CSIC)

University of Chicago

M. Mallorquín

Instituto de Astrofísica de Canarias

University of La Laguna

E. Nagel

University of Göttingen

A. Quirrenbach

Heidelberg-Königstuhl State Observatory

S. Reffert

Heidelberg-Königstuhl State Observatory

A. Reiners

University of Göttingen

I. Ribas

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

Spanish National Research Council (CSIC)

P. Schöfer

Spanish National Research Council (CSIC)

H. M. Tabernero

Centro de Astrobiologia (CAB)

IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos)

M. Zechmeister

University of Göttingen

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 685 A147

Subject Categories (SSIF 2011)

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/202349133

More information

Latest update

3/9/2025 1