We present precise Doppler measurements of four stars obtained during the past decade at Keck Observatory by the California Planet Survey (CPS). These stars, namely, HD 34445, HD 126614, HD 13931, and Gl 179, all show evidence for a single planet in Keplerian motion. We also present Doppler measurements from the Hobby-Eberly Telescope (HET) for two of the stars, HD 34445 and Gl 179, that confirm the Keck detections and significantly refine the orbital parameters. These planets add to the statistical properties of giant planets orbiting near or beyond the ice line, and merit followup by astrometry, imaging, and space-borne spectroscopy. Their orbital parameters span wide ranges of planetary minimum mass (M sin i = 0.38-1.9 M Jup ), orbital period (P = 2.87-11.5 yr), semi-major axis (a = 2.1-5.2 AU), and eccentricity (e = 0.02-0.41). HD 34445 b (P = 2.87 yr, M sin i = 0.79 M Jup , e = 0.27) is a massive planet orbiting an old, G-type star. We announce a planet, HD 126614 Ab, and an M dwarf, HD 126614 B, orbiting the metal-rich star HD 126614 (which we now refer to as HD 126614 A). The planet, HD 126614 Ab, has minimum mass M sin i = 0.38 M Jup and orbits the stellar primary with period P = 3.41 yr and orbital separation a = 2.3 AU. The faint M dwarf companion, HD 126614 B, is separated from the stellar primary by 489 mas (33 AU) and was discovered with direct observations using adaptive optics and the PHARO camera at Palomar Observatory. The stellar primary in this new system, HD 126614 A, has the highest measured metallicity ([Fe/H] = +0.56) of any known planetbearing star. HD 13931 b (P = 11.5 yr, M sin i = 1.88 M Jup , e = 0.02) is a Jupiter analog orbiting a near solar twin. Gl 179 b (P = 6.3 yr, M sin i = 0.82 M Jup , e = 0.21) is a massive planet orbiting a faint M dwarf. The high metallicity of Gl 179 is consistent with the planet-metallicity correlation among M dwarfs, as documented recently by Johnson & Apps.

Knowledge of the metallicities of M dwarfs rests predominantly on the photometric calibration of Bonfils and collaborators, which predicts that M dwarfs in the solar neighborhood, including those with known planets, are systematically metal poor compared to their higher-mass counterparts. We test this prediction using a volume-limited sample of low-mass stars, together with a subset of M dwarfs with high-metallicity, F, G, and K wide binary companions. We find that the Bonfils et al. photometric calibration systematically underestimates the metallicities of our high-metallicity M dwarfs by an average of 0.32 dex. We derive a new photometric metallicity calibration and show that M dwarfs with planets appear to be systematically metal rich, a result that is consistent with the metallicity distribution of FGK dwarfs with planets.

We present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission. We proceed by comparing KOI 961 to Barnards Star, a nearby, well-characterized mid-M dwarf. By comparing colors, optical and near-infrared spectra, we find remarkable agreement between the two, implying similar effective temperatures and metallicities. Both are metal-poor compared to the Solar neighborhood, have low projected rotational velocity, high absolute radial velocity, large proper motion and no quiescent Hα emission-all of which is consistent with being old M dwarfs. We combine empirical measurements of Barnard's Star and expectations from evolutionary isochrones to estimate KOI 961's mass (0.13 ± 0.05 M ⊙ ), radius (0.17 ± 0.04 R ⊙ ) and luminosity (2.40 × 10 −3.0±0.3 L ⊙ ). We calculate KOI 961's distance (38.7 ± 6.3 pc) and space motions, which, like Barnard's Star, are consistent with a high scale-height population in the Milky Way. We perform an independent multi-transit fit to the public Kepler light curve and significantly revise the transit parameters for the three planets. We calculate the false-positive probability for each planet-candidate, and find a less than 1 % chance that any one of the transiting signals is due to a background or hierarchical eclipsing binary, validating the planetary nature of the transits. The best-fitting radii for all three planets are less than 1 R ⊕ , with KOI 961.03 being Mars-sized (R P = 0.57 ± 0.18 R ⊕ ), and they represent some of the smallest exoplanets detected to date.

We report results of a search for planets around 500 main sequence stars using the Keck high resolution spectrometer which has provided Doppler precision of 3 m/s during the past 3 yr. We report 6 new strong planet candidates having complete Keplerian orbits, with periods ranging from 24 d to 3 yr. We also provide updated orbital parameters for 4 previously announced planets. Four of the six newly discovered planets have minimum Msini masses less than 2 Mjup, while the remaining two have Msini $\sim$ 5 Mjup. The distribution of planetary masses continues to exhibit a rise toward lower masses. The orbital eccentricities of the new planets range from 0.12 to 0.71 which also continues the ubiquity of high eccentricities. All 18 known extrasolar planets orbiting beyond 0.2 AU have eccentricities greater than $\sim$0.1. The current limiting Doppler precision of the Keck Doppler survey is 3 m/s per observation as determined from observations of both stable stars and residuals to Keplerian fits.Comment: 50 pages with 17 figure

Precise Doppler measurements from the Anglo-Australian Telescope (AAT) UCLES spectrometer reveal periodic Keplerian velocity variations in the stars HD 160691 and HD 27442. HD 160691 has a period of 743 days, a semiamplitude of 54 m s~1, and a high eccentricity, e \ 0.62, typical of extrasolar planets orbiting beyond 0.2 AU. The minimum (M sin i) mass of the companion is 1.97 and the M J , semimajor axis is 1.65 AU. HD 27442 has a 415 day period, a semiamplitude of 32 m s~1, and an eccentricity of 0.058. The minimum mass is 1.43 and the semimajor axis is 1.18 AU. This is the Ðrst M J , extrasolar planet orbiting beyond 0.2 AU that is in a circular orbit similar to solar system planets. The photon-limited precision of AAT/UCLES measurements is 3 m s~1 as demonstrated by stable stars and Keplerian Ðts to planet-bearing stars. In addition, we present conÐrmation of four previously announced planets.

We present four new exoplanets: HIP 14810 b & c, HD 154345 b, and HD 187123 c. The two planets orbiting HIP 14810, from the N2K project, have masses of 3.9 and 0.76 M Jup . We have searched the radial velocity time series of 90 known exoplanet systems and found new residual trends due to additional, long period companions. Two stars known to host one exoplanet have sufficient curvature in the residuals to a one planet fit to constrain the minimum mass of the outer companion to be substellar: HD 68988 c with 8 M Jup < m sin i < 20 M Jup and HD 187123 c with 3 M Jup < m sin i < 7 M Jup , both with P > 8 y. We have also searched the velocity residuals of known exoplanet systems for prospective low-amplitude exoplanets and present some candidates. We discuss techniques for constraining the mass and period of exoplanets in such cases, and for quantifying the significance of weak RV signals. We also present two substellar companions with incomplete orbits and periods longer than 8 y: HD 24040 b and HD 154345 b with m sin i < 20M Jup and m sin i < 10 M Jup , respectively.

We report the discovery of a brown dwarf that transits one member of the M+M binary system LHS 6343 AB every 12.71 days. The transits were discovered using photometric data from the Kepler public data release. The LHS 6343 stellar system was previously identified as a single high proper motion M dwarf. We use adaptive optics imaging to resolve the system into two low-mass stars with masses 0.370 ± 0.009 M and 0.30 ± 0.01 M , respectively, and a projected separation of 0. 55. High-resolution spectroscopy shows that the more massive component undergoes Doppler variations consistent with Keplerian motion, with a period equal to the transit period and an amplitude consistent with a companion mass of M C = 62.7 ± 2.4 M Jup . Based on our analysis of the transit light curve, we estimate the radius of the companion to be R C = 0.833 ± 0.021 R Jup , which is consistent with theoretical predictions of the radius of a >1 Gyr brown dwarf.

We report the confirmation and characterization of a transiting gas giant planet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally discovered by the Kepler mission. We use radial velocity measurements, adaptive optics imaging and near infrared spectroscopy to confirm the planetary nature of the transit events. KOI-254 b is the first hot Jupiter discovered around an M-type dwarf star. We also present a new model-independent method of using broadband photometry to estimate the mass and metallicity of an M dwarf without relying on a direct distance measurement. Included in this methodology is a new photometric metallicity calibration based on J − K colors. We use this technique to measure the physical properties of KOI-254 and its planet. We measure a planet mass of M P sin i = 0.505 M Jup , radius R P = 0.96 R Jup and semimajor axis a = 0.030 AU, based on our measured stellar mass M ⋆ = 0.59 M ⊙ and radius R ⋆ = 0.55 R ⊙ . We also find that the host star is metal-rich, which is consistent with the sample of M-type stars known to harbor giant planets.