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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Kinematics of RHB stars to trace the structure of the Galaxy
Red horizontal-branch (RHB) stars have been selected from the Hipparcoscatalogue to investigate their kinematics and spatial distribution.Hipparcos parallaxes, literature radial velocities and Hipparcos propermotions, together with models for the gravitational potential of theMilky Way allow a calculation of the actual velocity vectors and theorbits of the RHB stars. The velocity characteristics are used to definea halo population sample (HPS) in the collection of RHBs. The orbitslead statistically to an overall z-distance probability distribution,showing that the RHBs exhibit two populations, a disk one having a scaleheight of hdisk ≃ 0.6 kpc and a halo one of ≃4kpc. We have investigated the influence on our results of parallaxaccuracy and of a demarcation line in the HRD between the RHB and thered-giant (RG) star region. Neither of them show marked effects. We haveperformed the orbit analysis using the potential model of Allen &Santillan as well as of Dehnen & Binney. The results differ onlyslightly for the disk population, showing that these potential modelsare not a critical part of such orbit investigations. RHB scale heightvalues are smaller than those found earlier for sdB stars, most likelybecause the samples of stars used had different spatial distributions apriori. The data do not allow us to specify a trend in the kinematicbehaviour of star types along the horizontal branch.
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