Precise mass and radius determination for two new and one known Neptune-sized planets around G dwarf hosts

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ABSTRACT As part of the KESPRINT collaboration, we present the discovery and characterization of three exoplanets in the sub-Neptune to super-Neptune regime, spanning key regions of the exo-Neptunian landscape. TOI-1472 c and TOI-1648 b are newly discovered sub-Neptunes, while TOI-1472 b is a previously known super-Neptune for which we provide an improved mass measurement. These planets have orbital periods of 6–15 d and radii of 2.5–4.1 R$_{\oplus }$, probing regions where planet formation and atmospheric evolution remain poorly understood. We combine Transiting Exoplanet Survey Satellite transit photometry with ground-based radial velocities to determine precise masses, radii, and orbital properties. TOI-1472 b has a mass of $18.0^{+0.84}_{-0.85}$ M$_{\oplus }$ and a radius of $4.06 \pm 0.10$ R$_{\oplus }$, TOI-1472 c has a mass of $21.1^{+0.96}_{-0.99}$ M$_{\oplus }$ and a radius of $3.33 \pm 0.08$ R$_{\oplus }$, and TOI-1648 b has a mass of $7.4^{+1.1}_{-1.3}$ M$_{\oplus }$ and a radius of $2.54^{+0.14}_{-0.12}$ R$_{\oplus }$. The planets exhibit a range of eccentricities (0.041–0.178), indicating diverse evolutionary histories. TOI-1648 b, with a high transmission spectroscopy metric (${\rm TSM} \sim 59$), is a promising target for atmospheric characterization. Together, these three planets provide precise constraints on the structure, composition, and dynamical evolution of small to intermediate-sized exoplanets, enriching our understanding of the exo-Neptunian landscape.

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