Hat-P-3b:: a heavy-element-rich planet transiting a K dwarf star

We report the discovery of a Jupiter-size planet transiting a relatively bright (V = 11.56) and metal-rich early K dwarf star with a period of similar to 2.9 days. On the basis of follow-up photometry and spectroscopy we determine the mass and radius of the planet, HAT-P-3b, to be M and R. M-p 0.599 +/- 0.026 M-Jup and R-p 0.890 +/- 0.046 R-Jup. The relatively small size of the object for its mass implies the presence of about 75 M-circle plus worth of heavy elements (similar to 1/3 of the total mass) based on current theories of irradiated extrasolar giant planets, similar to the mass of the core inferred for the transiting planet HD 149026b. The bulk density of HAT-P-3b is found to be rho(p) p g cm, and the planet orbits the star at a distance of 0.03894 AU. Ephemerides for the transit centers are T-c 2,454,218.7594 +/- 0.0029 + N x (2.899703 +/- 0.000054) (HJD).