Searching for GEMS: Three warm Saturns and a super-Jupiter orbiting four early M-dwarfs

Abstract

We report the confirmation and characterization of four transiting giant planets orbiting early-M dwarfs discovered by the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey: TOI-7189 b, TOI-7265B b, TOI-7393 b, and TOI-7394B b. Joint modeling of TESS and ground-based photometry with precision radial velocities from the Habitable-zone Planet Finder and NEID spectrographs yields self-consistent orbital and physical parameters for all systems. The planets have short orbital periods ($P=1.25-4.17$ days), masses spanning from $0.5M_{\mathrm{J}}$ to $2.1M_{\mathrm{J}}$, and radii comparable to Jupiter ($0.95R_{\mathrm{J}}<R_p<1.02R_{\mathrm{J}}$). TOI-7189 b ($0.50M_{\mathrm{J}}$), TOI-7265B b ($0.71M_{\mathrm{J}}$), and TOI-7393 b ($0.61M_{\mathrm{J}}$) are Saturn-like in mass and density, whereas TOI-7394B b is a dense super-Jupiter ($2.10M_{\mathrm{J}}$, $\ddot{I}{}_p\approx 2.4$ g cm${}^{-3}$) on a 1.25-day orbit. All hosts are early-M dwarfs with a narrow range of stellar properties, enabling a controlled comparison of giant-planet outcomes around low-mass stars. Three systems orbit super-solar metallicity stars, while TOI-7393 ($[Fe/H]=-0.35\pm 0.16$) is the most metal-poor GEMS host identified to date, and exhibits kinematics approaching the thin/thick-disk transition, suggestive of an older stellar population. Together, these systems reveal substantial diversity in the masses and bulk properties of short-period giant planets orbiting early-M dwarfs, demonstrating that markedly different planetary outcomes can arise around stars with otherwise similar fundamental properties.

Published in AJ. 29 pages, 12 figures, 5 tables

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