Abstract

We report the discovery of TOI-172 b from the Transiting Exoplanet Survey Satellite (TESS) mission, a massive hot Jupiter transiting a slightly evolved G star with a 9.48-day orbital period. This is the first planet to be confirmed from analysis of only the TESS full frame images, because the host star was not chosen as a two-minute cadence target. From a global analysis of the TESS photometry and follow-up observations carried out by the TESS Followup Observing Program Working Group, TOI-172 (TIC 29857954) is a slightly evolved star with an effective temperature of T-eff = 5645 +/- 50 K, a mass of Ma(*) = 1.128(-0.061) (+0.065) M-circle dot, radius of R-* = 1.777(-0.044) (+0.047) R-circle dot, a surface gravity of log g(*) = 3.993(-0.028)(+0.027), and an age of 7.4(-1.5) (+1.6) Gyr Its planetary companion (TOI-172 b) has a radius of R-P = 0.965(-0.029) (+0.032) R-J, a mass of M-P = 5.42(-0).(20) (+0.22) M-J, and is on an eccentric orbit (e = 0.3806 (+0.0093)(-0.0090) TOI-172 b is one of the few known massive giant planets on a highly eccentric short-period orbit. Future study of the atmosphere of this planet and its system architecture offer opportunities to understand the formation and evolution of similar systems.