Doppler measurements from Subaru and Keck have revealed radial velocity variations in the V ¼ 8:15, G0 IV star HD 149026 consistent with a Saturn-mass planet in a 2.8766 day orbit. Photometric observations at Fairborn Observatory have detected three complete transit events with depths of 0.003 mag at the predicted times of conjunction. HD 149026 is now the second-brightest star with a transiting extrasolar planet. The mass of the star, based on interpolation of stellar evolutionary models, is 1:3 AE 0:1 M ; together with the Doppler amplitude K 1 ¼ 43:3 m s À1 , we derive a planet mass M sin i ¼ 0:36M J and orbital radius 0.042 AU. HD 149026 is chromospherically inactive and metal-rich with spectroscopically derived ½ Fe/ H ¼ þ0:36, T eA ¼ 6147 K, log g ¼ 4:26, and v sin i ¼ 6:0 km s À1 . Based on T eff and the stellar luminosity of 2.72 L , we derive a stellar radius of 1.45 R . Modeling of the three photometric transits provides an orbital inclination of 85N3 AE 1N0 and (including the uncertainty in the stellar radius) a planet radius of (0:725 AE 0:05) R J . Models for this planet mass and radius suggest the presence of a $67 M È core composed of elements heavier than hydrogen and helium. This substantial planet core would be difficult to construct by gravitational instability.

We have created specialized target lists for radial velocity surveys that are biased toward stars that (1) possess planets and (2) are easiest to observe with current detection techniques. We use a procedure that uniformly estimates fundamental stellar properties of Tycho 2 stars, with errors, using spline functions of broadband photometry and proper motion found in Hipparcos/Tycho 2 and 2MASS. We provide estimates of T eA and distance for 2:4 ; 10 6 Tycho 2 stars that lack trigonometric distances. For stars that appear to be FGK dwarfs, we also derive [Fe/ H] and identify unresolved binary systems with mass ratios 1:25 < M 1 /M 2 < 3:0. For FGK dwarfs with photometric error V < 0:05; or V < 9, our temperature model gives a 1 error of T ¼ þ58:7/À 65:9 K and our metallicity model gives a 1 error of ½Fe/ H ¼ þ0:13/À 0:14 dex. The binarity model can be used to remove 70% of doubles with 1:25 < M 1 /M 2 < 3:0 from a magnitude-limited sample of dwarfs at a cost of cutting 20% of the sample. Our estimates of distance and spectral type enable us to isolate 354,822 Tycho 2 dwarfs, 321,996 absent from Hipparcos, with giant contamination of 2.6% and 7.2%, respectively. Roughly 100,000 of these stars, not in Hipparcos, have sufficiently low photometric errors to retain 0.13-0.3 dex [ Fe/H] accuracy and 80-100 K temperature accuracy (1 ). Our metallicity estimates have been used to identify targets for N2K, a large-scale radial velocity search for hot jupiters, which has verified the errors presented here. The catalogs that we publish can be used to further large-scale studies of Galactic structure and chemical evolution and to provide potential reference stars for narrow-angle astrometry programs such as the Space Interferometry Mission and large-aperture optical interferometry.

We report the detection of five Jovian mass planets orbiting high metallicity stars. Four of these stars were first observed as part of the N2K program and exhibited low RMS velocity scatter after three consecutive observations. However, follow-up observations over the last three years now reveal the presence of -2longer period planets with orbital periods ranging from 21 days to a few years. HD 11506 is a G0V star with a planet of M sin i = 4.74 M JUP in a 3.85 year orbit. HD 17156 is a G0V star with a 3.12 M JUP planet in a 21.2 day orbit. The eccentricity of this orbit is 0.67, one of the highest known for a planet with a relatively short period. The orbital period for this planet places it in a region of parameter space where relatively few planets have been detected. HD 125612 is a G3V star with a planet of M sin i = 3.5 M JUP in a 1.4 year orbit. HD 170469 is a G5IV star with a planet of M sin i = 0.67 M JUP in a 3.13 year orbit. HD 231701 is an F8V star with planet of 1.08 M JUP in a 142 day orbit. All of these stars have supersolar metallicity. Three of the five stars were observed photometrically but showed no evidence of brightness variability. A transit search conducted for HD 17156 was negative but covered only 25% of the search space and so is not conclusive.

We present evidence that stars with planets exhibit statistically significant silicon and nickel enrichment over the general metal-rich population. We also present simulations which predict silicon enhancement of planet hosts within the context of the core-accretion hypothesis for giant planet formation. Because silicon and oxygen are both α-elements, [Si/Fe] traces [O/Fe], so the silicon enhancement in planet hosts predicts that these stars are oxygen-rich as well. We present new numerical simulations of planet formation by core accretion that establish the timescale on which a Jovian planet reaches rapid gas accretion, t rga , as a function of solid surface density σ solid : (t rga /1 Myr) = (σ solid /25.0 g cm −2 ) −1.44 . This relation enables us to construct Monte Carlo simulations that predict the fraction of star-disk systems that form planets as a function of [Fe/H], [Si/Fe], disk mass, outer disk radius and disk lifetime. Our simulations reproduce both the known planet-metallicity correlation and the planet-silicon correlation reported in this paper. The simulations predict that 16% of Solar-type stars form Jupiter-mass planets, in agreement with 12% predicted from extrapolation of the observed planet frequency-semimajor axis distribution. Although a simple interpretation of core accretion predicts that the planet-silicon correlation should be much stronger than the planet-nickel correlation, we observe the same degree of silicon and nickel enhancement in planet hosts. If this result persists once more planets have been discovered, it might indicate a complexity in the chemistry of planet formation beyond the simple accumulation of solids in the core accretion theory.

The N2K (''next 2000'') consortium is carrying out a distributed observing campaign with the Keck, Magellan, and Subaru telescopes, as well as the automatic photometric telescopes of Fairborn Observatory, in order to search for short-period gas giant planets around metal-rich stars. We have established a reservoir of more than 14,000 main-sequence and subgiant stars closer than 110 pc, brighter than V ¼ 10:5, and with 0:4 < B À V < 1:2. Because the fraction of stars with planets is a sensitive function of stellar metallicity, a broadband photometric calibration has been developed to identify a subset of 2000 stars with ½ Fe=H > 0:1 dex for this survey. We outline the strategy and report the detection of a planet orbiting the metal-rich G5 IV star HD 88133 with a period of 3.41 days, semivelocity amplitude K ¼ 35:7 m s À1 , and M sin i ¼ 0:29M J . Photometric observations reveal that HD 88133 is constant on the 3.415 day radial velocity period to a limit of 0.0005 mag. Despite a transit probability of 19.5%, our photometry rules out the shallow transits predicted by the large stellar radius.