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Astrophysical Journal


We announce the discovery of a highly inflated transiting hot Jupiter by the KELT-North survey. A global analysis including constraints from isochrones indicates that the V = 10.8 host star (HD 343246) is a mildly evolved, G dwarf with {T}{eff}={5754}-55+54 K, {log} g={4.078}-0.054+0.049, [{Fe}/{{H}}]=0.272+/- 0.038, an inferred mass {M}*={1.211}-0.066+0.078 {M}, and radius {R}*={1.67}-0.12+0.14 {R}. The planetary companion has a mass {M}{{P}}={0.867}-0.061+0.065 MJ, radius {R}{{P}}={1.86}-0.16+0.18 RJ, surface gravity {log} {g}{{P}}={2.793}-0.075+0.072, and density {ρ }{{P}}={0.167}-0.038+0.047 g cm-3. The planet is on a roughly circular orbit with semimajor axis a={0.04571}-0.00084+0.00096 AU and eccentricity e={0.035}-0.025+0.050. The best-fit linear ephemeris is {T}0=2456883.4803+/- 0.0007 {{BJD}}{TDB} and P=3.24406+/- 0.00016 days. This planet is one of the most inflated of all known transiting exoplanets, making it one of the few members of a class of extremely low density, highly irradiated gas giants. The low stellar {log} g and large implied radius are supported by stellar density constraints from follow-up light curves, as well as an evolutionary and space motion analysis. We also develop a new technique to extract high-precision radial velocities from noisy spectra that reduces the observing time needed to confirm transiting planet candidates. This planet boasts deep transits of a bright star, a large inferred atmospheric scale height, and a high equilibrium temperature of {T}{eq}={1675}-55+61 K, assuming zero albedo and perfect heat redistribution, making it one of the best targets for future atmospheric characterization studies.


planetary systems, stars: individual: HD 343246, Astrophysics - Earth and Planetary Astrophysics


This work is freely available courtesy of the American Astronomical Society and IOP Publishing.