An Eccentric Massive Jupiter Orbiting a Sub-Giant 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 \(T_{\rm eff}\) =\(5645\pm50\) K, a mass of \(M_{\star}\) = \(1.128^{+0.065}_{-0.061}\) \(M_{\odot}\), radius of \(R_{\star}\) = \(1.777^{+0.047}_{-0.044}\) \(R_{\odot}\), a surface gravity of \(\log\) \(g_{\star}\) = \(3.993^{+0.027}_{-0.028}\), and an age of \(7.4^{+1.6}_{-1.5}\) Gyr. Its planetary companion (TOI-172 b) has a radius of \(R_{\rm P}\) = \(0.965^{+0.032}_{-0.029}\) \(R_{\rm J}\), a mass of \(M_{\rm P}\) = \(5.42^{+0.22}_{-0.20}\) \(M_{\rm J}\), 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.