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

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.

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 allowed us to constrain the planetary masses and investigate their potential compositions.

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_e, and a mass of 3.33±0.36 Me, along with an inner super-Earth on a 7.59-day orbit with a radius of 1.25±0.07 R_e and a mass of 1.55±0.13 Me.

The TOI-4342 system hosts two sub-Neptunes of similar sizes (2.33±0.09 R_e and 2.35±0.09 R_e), with periods of 5.54 and 10.69 days. Their masses are measured to be 7.3±1.3 M_e and 4.8±1.4 M_e, respectively. The RVs also reveal a planet candidate around TOI-4342, likely non-transiting, with a period of 47.5 days and a minimum mass of 17.8±3.0 M_e.

With precise radii and masses, we derived bulk densities and explored possible compositions. The TOI-4336 A sub-Neptune 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.

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 TSM of 138, comparable to benchmark planets such as K2-18 b and LHS 1140 b.

Léna Parc, Charles Cadieux, Nolan Grieves, François Bouchy, Alexandrine L’Heureux, Caroline Dorn, Marie-Luise Steinmeyer, Elisa Delgado-Mena, René Doyon, Yolanda G.C. Frensch, Romain Allart, Etienne Artigau, Nicola Astudillo-Defru, Xavier Bonfils, Yann Carteret, Ryan Cloutier, Marion Cointepas, Karen A. Collins, Jose Renan De Medeiros, Xavier Delfosse, Xavier Dumusque, Tianjun Gan, Jonay I. González Hernández, Ravit Helled, Monika Lendl, Lucile Mignon, Angelica Psaridi, Nuno C. Santos, Richard P. Schwarz, Julia Venturini

Comments: 22 pages, 15 figures, resubmitted after corrections made following the initial review in A&A. Full abstract in the article
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2601.22115 [astro-ph.EP] (or arXiv:2601.22115v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2601.22115
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Submission history
From: Léna Parc
[v1] Thu, 29 Jan 2026 18:44:17 UTC (8,778 KB)
https://arxiv.org/abs/2601.22115

Astrobiology, exoplanet,