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TOI-2084 b and TOI-4184 b: Two new sub-Neptunes around M dwarf stars

K. Barkaoui, M. Timmermans, A. Soubkiou, B. V. Rackham, A. J. Burgasser, J. Chouqar, F. J. Pozuelos, K. A. Collins, S. B. Howell, R. Simcoe, C. Melis, K. G. Stassun, J. Tregloan-Reed, M. Cointepas, M. Gillon, X. Bonfils, E. Furlan, C. L. Gnilka, J. -M. Almenara, R. Alonso, Z. Benkhaldoun, M. Bonavita, F. Bouchy, A. Burdanov, P. Chinchilla, F. Davoudi, L. Delrez, O. Demangeon, M. Dominik, B.-O. Demory, J. De Wit, G. Dransfield, E. Ducrot, A. Fukui, T. C. Hinse, M. J. Hooton, E. Jehin, J. M. Jenkins, U. G. Jørgensen, D. W. Latham, L. J. Garcia, S. Carrazco-Gaxiola, M. Ghachoui, Y. Gómez Maqueo Chew, M. N. Günther, J. McCormac, F. Murgas, C. A. Murray, N. Narita, P. Niraula, P. P. Pedersen, D. Queloz, R. Rebolo López, G. R. Ricker, L. Sabin, S. Sajadian, N. Schanche, R. P. Schwarz, S. Seager, D. Sebastian, R. Sefako, S. Sohy, J. Southworth, G. Srdoc, S. J. Thompson, A. H. M. J. Triaud, R. K. Vanderspek, R. D. Wells, J. N. Winn, S. Zúñiga-Fernández

We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084 b, and TOI-4184b. We characterized the host stars by combining spectra from Shane/Kast and Magellan/FIRE, spectral energy distribution analysis, and stellar evolutionary models. In addition, we used Gemini-South/Zorro & -North/Alopeke high-resolution imaging, archival science images, and statistical validation packages to support the planetary interpretation. We performed a global analysis of multi-colour photometric data from TESS and ground-based facilities in order to derive the stellar and planetary physical parameters for each system. We find that TOI-2084 band TOI-4184 bare sub-Neptune-sized planets with radii of Rp = 2.47 ± 0.13 R and Rp = 2.43 ± 0.21 R, respectively. TOI-2084 b completes an orbit around its host star every 6.08 days, has an equilibrium temperature of Teq = 527 ± 8 K and an irradiation of Sp = 12.8 ± 0.8 S. Its host star is a dwarf of spectral M2.0 ± 0.5 at a distance of 114 pc with an effective temperature of Teff = 3550 ± 50 K, and has a wide, co-moving M8 companion at a projected separation of 1400 au. TOI-4184 b orbits around an M5.0 ± 0.5 type dwarf star (Kmag = 11.87) each 4.9 days, and has an equilibrium temperature of Teq = 412 ± 8 K and an irradiation of Sp = 4.8 ± 0.4 S. TOI-4184 is a metal poor star ([Fe/H] = −0.27 ± 0.09 dex) at a distance of 69 pc with an effective temperature of Teff = 3225 ± 75 K. Both planets are located at the edge of the sub-Jovian desert in the radius-period plane. The combination of the small size and the large infrared brightness of their host stars make these new planets promising targets for future atmospheric exploration with JWST.

techniques: photometric / stars: low-mass

Astronomy & Astrophysics
2023 September

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia