ABSTRACT. 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 ~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_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_⊕ worth of heavy elements (~ 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 ρ_p = 1.06 ± 0.17 g cm^-3, 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 × (2.899703 ± 0.000054) (HJD).

Subject headings: binaries: spectroscopic; planetary systems; stars: fundamental parameters; stars: individual (HAT-P-3); techniques: spectroscopic

Print publication: Issue 2 (2007 September 10)
Received 2007 June 14, accepted for publication 2007 July 23
Published 2007 August 17