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The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Speckle observations of binary systems measured by Hipparcos
From speckle observations made with the PISCO speckle camera at the Picdu Midi Observatory, we present high angular resolution astrometric datafor 43 binary stars already observed by the Hipparcos satellite. Thissample consists of mainly new Hipparcos eclipsing binaries with a visualcompanion closer than one arcsecond, chosen with the aim to study thedynamical implications of a third component on the observationalparameters of the eclipsing system. In addition, we also included aselection of close visual binaries with few speckle data in order toanalyse possible systematic departures between the speckle and thenon-speckle orbits. The reduction method and the results are presentedin detail. For the close visual binaries we confront our observationswith the ephemerides based on the best known orbits. For the wide visualbinaries the confrontation is made directly with the Hipparcos data. Ourobservations are consistent both with previous speckle data and withmost of the Hipparcos measurements. Based on observations made with theTélescope Bernard Lyot at the Pic du Midi Observatory, France andon data obtained by the Hipparcos astrometry satellite. This work hasalso made use of the Simbad database, operated at CDS, Strasbourg,France.
| Interstellar reddening in the Southern Hemisphere. I - The UVBY beta observations
The uvby-beta photometric data obtained from a Southern Hemisphereobservational project is presented. A uvby-beta photometric network ofnearly 3900 A and early F stars has been established with the intentthat the stars serve as 'space probes' for measurements of interstellarreddening.
| CCD measurements of visual binaries
CCD measurements of visual double stars were obtained with the ESO 1.5 mdanish reflector. All binaries observed are candidates for the HIPPARCOSInput Catalogue. More than 400 observations have been made in four clearnights. The accuracy obtained is comparable to the accuracy of thephotographic technique, but the observing and reduction times are oneorder of magnitude smaller.
| Maximum separations among cataloged binaries
The paper classifies many of the widest common-motion binaries listed inthe Aitken catalog and list 72 physical pairs with known photoelectricphotometry, 31 physical pairs without good photometry, and 27 opticalpairs. As a function of primary types, the physical systems have upperlimits to their separations that are exceeded by some of the opticalpairs. The fact that optical pairs occur with larger separations impliesthat the limits are real ones and not just catalog limitations. Thoselimits (in AU) are expressed by 2500 M1 exp 1.54 for B5-KO main-sequenceprimaries. The same limits hold for the Trapezium and hierarchicalsystems studied previously.
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| Сазвежђа: | Орао |
| Ректацензија: | 19h28m12.93s |
| Deклинација: | -09°32'15.9" |
| Apparent магнитуда: | 8.305 |
| Даљина: | 216.45 parsecs |
| Proper motion RA: | 7 |
| Proper motion Dec: | -28.5 |
| B-T magnitude: | 8.751 |
| V-T magnitude: | 8.342 |
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