Frensch, Yolanda G.C., Bouchy, François, Lo Curto, Gaspare, Ulmer-Moll, Solene, Sousa, Sérgio G., Santos, Nuno C., Stassun, Keivan Guadalupe, Watkins, Cristilyn N., Chakraborty, Hritam, & Barkaoui, Khalid. (2025). Three hot Jupiters transiting K-dwarfs with significant heavy element masses. Astronomy and Astrophysics, 700, A118. https://doi.org/10.1051/0004-6361/202553879
Planet formation models predict that short-period gas giants (also called hot Jupiters) should be very rare around low-mass stars (with temperatures below 4965 K). Still, a small number have been found, though they are less common than around hotter stars.
In this study, we combined data from the Transiting Exoplanet Survey Satellite (TESS) with ground-based imaging, photometry, and high-resolution spectroscopy from the CORALIE spectrograph to confirm and characterize giant planets orbiting mid- to late-K dwarfs. Radial velocity (RV) measurements were used to confirm the presence of planetary companions.
We report the discovery of three giant planets transiting K-dwarf stars. In the TOI-2969 system, a planet with a mass of 1.16 ± 0.04 Jupiter masses and a radius of 1.10 ± 0.08 Jupiter radii orbits its K3V host star every 1.82 days. The TOI-2989 system contains a 3.0 ± 0.2 Jupiter-mass planet with a radius of 1.12 ± 0.05 Jupiter radii, orbiting its K4V star in 3.12 days. The K4V star TOI-5300 hosts a 0.6 ± 0.1 Jupiter-mass planet with a radius of 0.88 ± 0.08 Jupiter radii and an orbital period of 2.3 days. These planets have equilibrium temperatures between 1001 and 1186 K, placing them in the hot Jupiter category, although they do not show signs of radius inflation.
Interestingly, the estimated heavy element masses within their interiors—90 ± 30, 114 ± 30, and 84 ± 21 Earth masses—are much higher than those reported for most hot Jupiters around K-dwarfs.
These results expand our understanding of the small but important population of massive companions around low-mass stars.
HR diagram of all Gaia DR3 nearby stars with parallax π ≥ 10 mas, where the colors indicate log(g). The three stars presented in this work are overplotted and visible on the main sequence.