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

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 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 sstarf = ${1.128}_{-0.061}^{+0.065}$ M ⊙, radius of R sstarf = ${1.777}_{-0.044}^{+0.047}$ R ⊙, a surface gravity of log g sstarf = ${3.993}_{-0.028}^{+0.027}$, and an age of ${7.4}_{-1.5}^{+1.6}\ \mathrm{Gyr}$. 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.