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A Substellar Companion in a 1.3 yr Nearly Circular Orbit of HD 16760
We report the detection of a substellar companion orbiting the G5 dwarfHD 16760 from the N2K sample. Precise Doppler measurements of the starfrom Subaru and Keck revealed a Keplerian velocity variation with aperiod of 466.47 ± 0.35 d, a semiamplitude of 407.71 ±0.84 m s-1, and an eccentricity of 0.084 ±0.003. Adopting a stellar mass of 0.78 ± 0.05 M sun,we obtain a minimum mass for the companion of 13.13 ± 0.56 MJUP, which is close to the planet/brown-dwarf transition, andthe semimajor axis of 1.084 ± 0.023 AU. The nearly circular orbitdespite the large mass and intermediate orbital period makes thiscompanion unique among known substellar companions.
| Two Exoplanets Discovered at Keck Observatory
We present two exoplanets detected at Keck Observatory. HD 179079 is aG5 subgiant that hosts a hot Neptune planet with M sin i = 27.5 M? in a 14.48 days, low-eccentricity orbit. The stellarreflex velocity induced by this planet has a semiamplitude of K = 6.6 ms-1. HD 73534 is a G5 subgiant with a Jupiter-likeplanet of M sin i = 1.1 M Jup and K = 16 ms-1 in a nearly circular 4.85 yr orbit. Both stars arechromospherically inactive and metal-rich. We discuss a known, classicalbias in measuring eccentricities for orbits with velocitysemiamplitudes, K, comparable to the radial velocity uncertainties. Forexoplanets with periods longer than 10 days, the observed exoplaneteccentricity distribution is nearly flat for large amplitude systems (K> 80 m s-1), but rises linearly toward loweccentricity for lower amplitude systems (K > 20 ms-1).Based on observations obtained at the Keck Observatory, which isoperated by the University of California.
| Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants
We present the parameters of 891 stars, mostly clump giants, includingatmospheric parameters, distances, absolute magnitudes, spatialvelocities, galactic orbits and ages. One part of this sample consistsof local giants, within 100 pc, with atmospheric parameters eitherestimated from our spectroscopic observations at high resolution andhigh signal-to-noise ratio, or retrieved from the literature. The otherpart of the sample includes 523 distant stars, spanning distances up to1 kpc in the direction of the North Galactic Pole, for which we haveestimated atmospheric parameters from high resolution but lowsignal-to-noise Echelle spectra. This new sample is kinematicallyunbiased, with well-defined boundaries in magnitude and colours. Werevisit the basic properties of the Galactic thin disk as traced byclump giants. We find the metallicity distribution to be different fromthat of dwarfs, with fewer metal-rich stars. We find evidence for avertical metallicity gradient of -0.31 dex kpc-1 and for atransition at ~4-5 Gyr in both the metallicity and velocities. Theage-metallicity relation (AMR), which exhibits a very low dispersion,increases smoothly from 10 to 4 Gyr, with a steeper increase for youngerstars. The age-velocity relation (AVR) is characterized by thesaturation of the V and W dispersions at 5 Gyr, and continuous heatingin U.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
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