Searching for GEMS TOI-5916 b & TOI-6158 b are Two Saturn-density Planets Orbiting M2 Dwarfs

We confirm the planetary nature of (1) TOI-5916 b and (2) TOI-6158 b, two giant exoplanets around M-dwarf stars (GEMS), both discovered by the Transiting Exoplanet Survey Satellite. 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 R₁ = 11.8^+0.52_-0.51R_⊕ (1.05 ± 0.05RJ) and R₂ + 10.4^+2.70_-1.11R_⊕(0.93+0.24-0.10Rj), their masses are M₁ = 219 ± 28M_⊕(0.688^+0.087_-0.088M_j) and M2 = 135⁺¹⁹_-18M_⊕(0.425^+0.060-_0.058M_j), and their orbital periods are
and P₁ = 2.36712341^+0.0000033_-0.0000032 days and P₂ = 3.04468990^+0.00000551_-0.000000534 days. Both planets have Saturn-like densities (ρ1 = 0.73^+0.14_-0.13 gcm^-3, ρ2 = 0.66⁺⁰⁴¹_-0.23 gcm^-3), which is consistent with the densities of most other GEMS, and with warm gas giants in general. 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.