TOI-2494 c and TOI-5143 c: A Hot Saturn and a Hot Jupiter with Interior Planetary Companions

Abstract We present the TESS-based discoveries of planetary systems orbiting the late G dwarfs TOI-2494 and TOI-5143, each of which harbors a hot giant planet and a smaller interior planet. TOI-2494 hosts a transiting mini-Neptune ( P = 2.41 days, R P = 2.3 5 − 0.15 + 0.16 R ⊕ ) and a hot Saturn ( P = 8.38 days) with grazing transits, while TOI-5143 hosts a transiting mini-Neptune ( P = 2.38 days, R P = 2.7 3 − 0.17 + 0.19 R ⊕ ) and a hot Jupiter ( P = 5.21 days) with grazing transits. We measure the masses of TOI-2494 c (80 ± 19 M ⊕ ) and TOI-5143 c (208 ± 14 M ⊕ ), place upper limits on the masses of the smaller planets, and explore the architectures of the planetary systems. TOI-2494 c and TOI-5143 c join a small but growing number of short-period giant planets known to be flanked by smaller companions. While the absence of close neighbors to most hot Jupiters would be consistent with disruptive dynamical evolution, the presence of nearby small planets in some hot Jupiter systems points to a separate, dynamically quiet formation pathway. In support of this conclusion, we present preliminary evidence that hot giant planets with small nearby companions tend to have low mutual orbital inclinations, consistent with the mutual inclination distribution of the dynamically quiet population of compact systems of multiple super-Earths and mini-Neptunes.