1. TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization
- Author
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Goffo, E., Chaturvedi, P., Murgas, F., Morello, G., Orell-Miquel, J., Acuña, L., Peña-Moñino, L., Pallé, E., Hatzes, A. P., Geraldía-González, S., Pozuelos, F. J., Lanza, A. F., Gandolfi, D., Caballero, J. A., Schlecker, M., Pérez-Torres, M., Lodieu, N., Schweitzer, A., Hellier, C., Jeffers, S. V., Duque-Arribas, C., Cifuentes, C., Béjar, V. J. S., Daspute, M., Dubois, F., Dufoer, S., Esparza-Borges, E., Fukui, A., Hayashi, Y., Herrero, E., Mori, M., Narita, N., Parviainen, H., Tal-Or, L., Vanaverbeke, S., Hermelo, I., Amado, P. J., Dreizler, S., Henning, Th., Lillo-Box, J., Luque, R., Mallorquín, M., Nagel, E., Quirrenbach, A., Reffert, S., Reiners, A., Ribas, I., Schöfer, P., Tabernero, H. M., and Zechmeister, M.
- Subjects
Astrophysics - Earth and Planetary Astrophysics - Abstract
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_Earth (5% precision), which together with a mass of Mb=5.4 +/- 1.1 M_Earth (20% precision), results in a bulk density of rho = 1.85+0.51-0.44 g cm-3 (28% precision), aligning the discovery with a volatile-rich planet. Our interior structure retrieval with a pure water envelope yields a minimum water mass fraction of 46% (1-sigma). TOI-4438 b is a volatile-rich mini-Neptune with likely H/He mixed with molecules, such as water, CO_2, and CH_4. 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 T_eq = 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., Comment: Accepted for publication on Astronomy & Astrophysics
- Published
- 2024