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

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-1472c and TOI-1648b are newly discovered sub-Neptunes, while TOI-1472b is a previously known super-Neptune for which we provide an improved mass measurement. These planets have orbital periods of 6--15 days and radii of 2.5--4.1 R${}_{\oplus }$, probing regions where planet formation and atmospheric evolution remain poorly understood. We combine TESS transit photometry with ground-based radial velocities to determine precise masses, radii, and orbital properties. TOI-1472b has a mass of $18.0_{-0.85}^{+0.84}$ M${}_{\oplus }$ and a radius of $4.06\pm 0.10$ R${}_{\oplus }$, TOI-1472c has a mass of $21.1_{-0.99}^{+0.96}$ M${}_{\oplus }$ and a radius of $3.33\pm 0.08$ R${}_{\oplus }$, and TOI-1648b has a mass of $7.4_{-1.3}^{+1.1}$ M${}_{\oplus }$ and a radius of $2.54_{-0.12}^{+0.14}$ R${}_{\oplus }$. The planets exhibit a range of eccentricities (0.041--0.178), indicating diverse evolutionary histories. TOI-1648b, with a high Transmission Spectroscopy Metric (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.