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.
Categories: astro-ph.EP astro-ph.SR