Discovery and Characterization of an Eccentric, Warm Saturn Transiting the Solar Analog TOI-4994

Abstract

We present the detection and characterization of TOI-4994b (TIC 277128619b), a warm Saturn-sized planet discovered by the NASA Transiting Exoplanet Survey Satellite (TESS). TOI-4994b transits a G-type star (V = 12.6 mag) with a mass, radius, and effective temperature of $M_{\star }=1.005_{-0.061}^{+0.064}{M}_{\odot }$, $R_{\star }=1.055_{-0.037}^{+0.040}{R}_{\odot }$, and $T_{\mathrm{eff}}=5640\pm 110$ K. We obtained follow-up ground-based photometry from the Las Cumbres Observatory (LCO) and the Antarctic Search for Transiting ExoPlanets (ASTEP) telescopes, and we confirmed the planetary nature of TOI-4994b with multiple radial velocity observations from the PFS, CHIRON, HARPS, FEROS, and CORALIE instruments. From a global fit to the photometry and radial velocities, we determine that TOI-4994b is in a 21.5-day, eccentric orbit ($e=0.32\pm 0.04$) and has a mass of $M_P=0.280_{-0.034}^{+0.037}{M}_J$, a radius of $R_P=0.762_{-0.027}^{+0.030}{R}_J$, and a Saturn-like bulk density of $\ddot{I}{}_p=0.78_{-0.14}^{+0.16}$ $g/c{\mathrm{m}}^3$. We find that TOI-4994 is a potentially viable candidate for follow-up stellar obliquity measurements. TOI-4994b joins the small sample of warm Saturn analogs and thus sheds light on our understanding of these rare and unique worlds.

17 pages, 10 figures. Accepted to AJ