paper

Searching for GEMS: TOI-5916 b & TOI-6158 b are two Saturn-density planets orbiting M2 dwarfs

arXiv:2510.11798 · doi:10.3847/1538-3881/ae844e

Abstract

We confirm the planetary nature of (1) TOI-5916 b and (2) TOI-6158 b, two Exoplanets Transiting M-dwarf Stars (GEMS), both discovered by the Transiting Exoplanet Survey Satellite (TESS). Both systems were confirmed with ground-based photometry (Red Buttes Observatory and Swope, respectively) and radial velocity data from the Habitable-zone Planet Finder. Their radii are $R_{1} = 11. 8_{- 0.51}^{+ 0.52} R_{\oplus}$ and $R_{2} = 10. 4_{- 1.11}^{+ 2.70} R_{\oplus}$ and masses are $M_{1} = 219 \pm 28 M_{\oplus}$ and $M_{2} = 13 5_{- 18}^{+ 19} M_{\oplus}$ . Both planets have Saturn-like densities ( $I ¨ _{1} = 0.7 3_{- 0.13}^{+ 0.14} g cm^{- 3}$ , $I ¨ _{2} = 0.6 6_{- 0.23}^{+ 0.41} g cm^{- 3}$ ), which appears to be a growing trend among GEMS systems and, more generally, warm Jupiters. In confirming both of these exoplanets, we add to the growing evidence for a population of Saturn-density planets among the GEMS systems. We also find evidence for a preliminary trend in which GEMS exhibit systematically closer orbits compared to FGK giants.

Submitted to AAS Journals