HAT-P-14b: A 2.2M _J exoplanet transiting a bright F star

We report the discovery of HAT-P-14b, a fairly massive transiting extrasolar planet orbiting the moderately bright star GSC 3086-00152 (V = 9.98), with a period of P = 4.627669 0.000005days. The transit is close to grazing (impact parameter 0.891^+0.007 _-0.008) and has a duration of 0.0912 0.0017days, with a reference epoch of mid-transit of T_c = 2, 454, 875.28938 ± 0.00047 (BJD). The orbit is slightly eccentric (e = 0.107 ± 0.013), and the orientation is such that occultations are unlikely to occur. The host star is a slightly evolved mid-F dwarf with a mass of 1.386 ± 0.045M _⊙, a radius of 1.468 ± 0.054R _⊙, effective temperature 6600 ± 90K, and a slightly metal-rich composition corresponding to [Fe/H] = +0.11 0.08. The planet has a mass of 2.232 ± 0.059M _J and a radius of 1.150 ± 0.052R _J, implying a mean density of 1.82 ± 0.24g cm^-3. Its radius is well reproduced by theoretical models for the 1.3Gyr age of the system if the planet has a heavy-element fraction of about 50M _⊕ (7% of its total mass). The brightness, near-grazing orientation, and other properties of HAT-P-14 make it a favorable transiting system to look for changes in the orbital elements or transit timing variations induced by a possible second planet, and also to place meaningful constraints on the presence of sub-Earth mass or Earth-mass exomoons, by monitoring it for transit duration variations.