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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.
| Mesures de vitesses radiales. VIII. Accompagnement AU sol DU programme d'observation DU satellite HIPPARCOS
We publish 1879 radial velocities of stars distributed in 105 fields of4^{\circ} \times 4^{\circ}. We continue the PPO series \cite[(Fehrenbachet al. 1987;]{Feh87} \cite[Duflot et al. 1990, 1992 and 1995),]{Du90}using the Fehrenbach objective prism method. Table 1 only available inelectronic form at CDS via to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984
Stellar radial velocity observations made with the large vacuumhigh-dispersion photoelectric radial velocity spectrometer at FickObservatory are reported. This includes nearly 2000 late-type starsobserved during 585 nights. Gradual modifications to this instrumentover its first eight years of operation have reduced the observationalerror for high-quality dip observations to + or - 0.8 km/s.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | ברבור |
| התרוממות ימנית: | 19h58m02.38s |
| סירוב: | +40°55'36.6" |
| גודל גלוי: | 7.321 |
| מרחק: | 191.571 פארסק |
| תנועה נכונה: | 9.2 |
| תנועה נכונה: | 15.9 |
| B-T magnitude: | 8.411 |
| V-T magnitude: | 7.411 |
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