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7 result(s) for "BORKOVA, D"
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About Compiled Catalogue of Spectroscopically Determined \\(\\alpha\\)-Elements Abundances for Stars with Accurate Parallaxes
We present a new version of the compiled catalogue of nearby stars for which was published the spectoscopically determined effective temperatures, surface gravities, and abundances of iron, magnesium, calcium, silicon, and titanium. Distances, velocity components, galactic orbital elements, and ages was calculated for all stars. The atmospheric parameters and iron abundances were found from 4700 values in 136 publications, while relative abundances of alpha-elements were found from 2800 values in 81 publications for ~2000 dwarfs and giants using a three-step iteration averaging procedure, with weights assigned to each source of data as well as to each individual determination and taking into account systematic deviations of each scale relative to the reduced mean scale. The estimated assumed completeness for data sources containing more than five stars, up to late April 2007, exceeds 90%. For the vast majority of stars in the catalogue, the spatial-velocity components were derived from modern high-precision astrometric observations, and their Galactic orbit elements were computed using a three-component model of the Galaxy, consisting of a disk, a bulge, and a massive extended halo. Ages was determined for dwarfs and subgiants using Yale isochrones~2004. For this purpose the original codes was developed, based on interpolation with the 3D-spline functions of theoretical isochrones, and with subsequent interpolation in metallicity and abundances of \\alpha-elements.
Local Surface Density of the Galactic Disk from a 3-D Stellar Velocity Sample
We have re-estimated the surface density of the Galactic disk in the solar neighborhood within \\(\\pm\\) 0.4 kpc of the Sun using parallaxes and proper motions of a kinematically and spatially unbiased sample of 1476 old bright red giant stars from the Hipparcos catalog with measured radial velocities from Barbier-Brossat & Figon (2000). We determine the vertical distribution of the red giants as well as the vertical velocity dispersion of the sample, (14.4 \\(\\pm\\) 0.26 km/sec), and combine these to derive the surface density of gravitating matter in the Galactic disk as a function of the galactic coordinate \\(z\\). The surface density of the disk increases from 10.5 \\(\\pm\\) 0.5 \\(M_{\\odot}\\) / pc\\(^2\\) within \\(\\pm\\) 50 pc to 42 \\(\\pm\\) 6 \\(M_{\\odot}\\) / pc\\(^2\\) within \\(\\pm\\) 350 pc. The estimated volume density of the galactic disk within \\(\\pm\\) 50 pc is about 0.1 \\(M_{\\odot}\\) / pc\\(^3\\) which is close to the volume density estimates of the observed baryonic matter in the solar neighborhood.