KELT-3b: A Hot Jupiter Transiting a V = 9.8 Late-F Star

We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477^(+0.066)_(-0.067) M_J, radius of 1.345 ± 0.072 R J, and an orbital period of 2.7033904 ± 0.000010 days. The host star, KELT-3, is a V = 9.8 late F star with M* = 1.278^(+0.063)_(-0.061) M⊙, R* = 1.472^(+0.065)_(-0.067) R⊙, T_(eff) = 6306^(+50)_(-49) K, log(g) = 4.209^(+0.033)_(-0.031), and [Fe/H] = 0.044^(+0.080)_(-0.082), and has a likely proper motion companion. KELT-3b is the third transiting exoplanet discovered by the KELT survey, and is orbiting one of the 20 brightest known transiting planet host stars, making it a promising candidate for detailed characterization studies. Although we infer that KELT-3 is significantly evolved, a preliminary analysis of the stellar and orbital evolution of the system suggests that the planet has likely always received a level of incident flux above the empirically identified threshold for radius inflation suggested by Demory & Seager