Densities of small planets around the M dwarfs TOI-4336 A and TOI-4342 with ESPRESSO: Three sub-Neptunes, one super-Earth, and a Neptune-mass candidate

Article Article scientifique Article Densities of small planets around the M dwarfs TOI-4336 A and TOI-4342 with ESPRESSO: Three sub-Neptunes, one super-Earth, and a Neptune-mass candidate eng 2026-04-01 2026-04 author Parc Léna Romane Elisa 0000-0002-7382-1913 402592 Département d'astronomie (ASTRO) author Cadieux Charles 0000-0001-9291-5555 406247 Département d'astronomie (ASTRO) author Grieves Nolan 0000-0001-8105-0373 930970 author Bouchy François 0000-0002-7613-393X 133687 Département d'astronomie (ASTRO) author L’Heureux Alexandrine 0009-0005-6135-6769 author Dorn Caroline 0000-0001-6110-4610 author Steinmeyer Marie-Luise author Delgado-Mena Elisa 0000-0003-4434-2195 author Doyon René author Frensch Yolanda Gerardina Cécile 0000-0003-4009-0330 975671 author Allart Romain author Artigau Etienne 0000-0003-3506-5667 author Astudillo-Defru Nicola 0000-0002-8462-515X author Bonfils Xavier author Carteret Yann 0000-0002-6159-6528 author Cloutier Ryan author Cointepas Marion 0009-0001-6168-2178 author Collins Karen A. 0000-0001-6588-9574 author De Medeiros Jose Renan 0000-0001-8218-1586 author Delfosse Xavier 0000-0001-5099-7978 author Dumusque Xavier 0000-0002-9332-2011 author Gan Tianjun 0000-0002-4503-9705 author González Hernández Jonay I. 0000-0002-0264-7356 author Helled Ravit 0000-0001-5555-2652 author Lendl Monika 0000-0001-9699-1459 715612 Département d'astronomie (ASTRO) author Mignon Lucile 0000-0002-5407-3905 984034 author Psaridi Angeliki 0000-0002-4797-2419 942153 author Santos Nuno C. 0000-0003-4422-2919 author Schwarz Richard P. 0000-0001-8227-1020 author Venturini Julia 0000-0001-9527-2903 984012 Département d'astronomie (ASTRO) A81 10.1051/0004-6361/202558308 0004-6361 https://www.aanda.org/10.1051/0004-6361/202558308 Context . Characterizing the masses, radii, and compositions of small planets orbiting M dwarfs is key to understanding their formation and identifying the best targets for atmospheric follow-up with facilities such as JWST. Aims . We present the characterization of two planetary systems orbiting the M dwarfs TOI-4336 A (M3.5V) and TOI-4342 (M0V), each hosting two transiting planets previously validated with TESS and ground-based observations. Methods . We refined the photometry of the TOI-4342 system using TESS and LCOGT data, and characterized the host stars with NIRPS and ESPRESSO spectroscopy. High-precision ESPRESSO radial velocities (RVs) allowed us to constrain the planetary masses and investigate their potential compositions. Results . The TOI-4336 A system is composed of a sub-Neptune with a period of 16.34 days, a radius of 2.14 ± 0.08 R ⊕ , and a mass of 3.33 ± 0.36 M ⊕ , along with an inner super-Earth on a 7.59-day orbit with a radius of 1.25 ± 0.07 R ⊕ and a mass of 1.55 ± 0.13 M ⊕ . The TOI-4342 system hosts two sub-Neptunes of similar sizes (2.33 ± 0.09 R ⊕ and 2.35 ± 0.09 R ⊕ ), with periods of 5.54 and 10.69 days. Their masses are measured to be 7.3 ± 1.3 M ⊕ and 4.8 ± 1.4 M ⊕ , respectively. The RVs also reveal a planet candidate around TOI-4342, most likely non-transiting, with a period of 47.5 days and a minimum mass of 17.8 ± 3.0 M ⊕ . Conclusions . With precise radii and masses, we derived bulk densities and explored possible compositions. The TOI-4336 A subNeptune and super-Earth have densities of 1.87 ± 0.30 and 4.35 ± 0.79 g cm −3 , while the two similar-sized sub-Neptunes in TOI-4342 show distinct densities of 3.18 ± 0.67 and 2.01 ± 0.63 g cm −3 . Using an inference model, we find that TOI-4336 A b, TOI-4342 b, and TOI-4342 c have an atmosphere mass fraction (AMF) of ∼3.7%, ∼1.8%, and ∼2.9%, respectively, while the super-Earth TOI-4336 A c could contain ∼2% of water or have a core-to-mass fraction (CMF) of ∼31%. All four planets are excellent targets for future atmospheric characterization with JWST, and their multi-planet nature makes them especially interesting for comparative planetology. Notably, TOI-4336 A b stands out as one of the best known targets in its size and temperature regime, with a transmission spectroscopy metric (TSM) of 138, comparable to benchmark planets such as K2-18 b and LHS 1140 b. Its inner sibling, TOI-4336 A c, may also be of interest for emission spectroscopy and exploring the “cosmic shoreline”, similarly to the Rocky Worlds DDT JWST program. Dewey 520 Unidad de Excelencia Maria de Maeztu CEX2020-001058-M Fundacao para a Cencia e a Tecnologia UIDB/04434/2020 Agencia Estatal de Investigación RyC2022-035854-I FONDECYT 1240916 TESS mission s3449 CNPq 308928/2019-9 Spanish Ministry of Science, Innovation and Universities PID2020-117493GB-I00 European Commission Signal Correction to Reveal other Earths 851555 SCORE EU H2020 Swiss National Science Foundation NCCR PlanetS: Origin, evolution and characterisation of planets (phase II) 182901 CH Swiss National Science Foundation NCCR PlanetS: Origin, evolution and characterisation of planets (phase III) 205606 CH Swiss National Science Foundation SPECTRE: Spectra post-Processing to Enable the Characterisation of TRue Earths 215200 CH French National Research Agency (ANR) Optimising Radial Velocity ExTraction ANR-24-CE49-3397 ORVET FR 26 Département d'astronomie 12 false Astronomy & astrophysics 708 5652ef0b-efb5-4433-8da7-59a22ffa0753 Article (Published version) Public Article_scientifique_from_crossref.pdf 7114602 application/pdf CC BY-4.0 9173d99f505891dc92320da26bbf1405710f2b0ff8a0f31c402f8abc6aac94d6 openAccess Faculté des sciences / Département d'astronomie

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Densities of small planets around the M dwarfs TOI-4336 A and TOI-4342 with ESPRESSO: Three sub-Neptunes, one super-Earth, and a Neptune-mass candidate	Astronomy & astrophysics			2026	6	7

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Cadieux, Charles