An Eccentric Massive Jupiter Orbiting a Subgiant on a 9.5-day Period Discovered in the Transiting Exoplanet Survey Satellite Full Frame Images

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 Follow-up 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 M _⋆ = {1.128}_-0.061^+0.065 M _⊙, radius of R _⋆ = {1.777}_-0.044^+0.047 R _⊙, 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}_-0.0090^+0.0093). 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.