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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
| Optical images of MCLD123.5+24.9: a cloud illuminated by the North star?
We present B R I images of a 1degr {x}1degr field centered on themolecular cloud (MCLD123.5+24.9) located in the large infrared cirrusknown as the Polaris Flare. The optical images are compared with IRASimages and an extinction map derived from stellar reddenings. We analysethe possibility for the North star (HD8890), only 1degr North of thefield, to be the source of MCLD123.5+24.9 optical emission. For widelyaccepted values of the dust albedo (omega = 0.6) and the assymetryparameter of the Henyey Greenstein phase function (0.7
| Polaris Today
Not Available
| Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
| The reddening of Polaris
The B-V color excess of Polaris is obtained by using uvby-betaphotometry of 11 field stars within 0.75 deg of arc of Polaris anddereddening the field stars with the various color calibrations of theStromgren system. An apparent distance of 109 pc is estimated forPolaris, and a color excess of E(B-V) equals 0.02 + or - 0.02 is found.This result is taken as supporting the claims that Polaris is unreddenedor at worst very slightly reddened and therefore lies on the red edge ofthe Cepheid instability strip, as is expected for a small-amplitudeCepheid.
| Mean places for 42 of the brighter stars within 1 of the NCP-1978.0.
Not Available
| Photo-electric observations of 31 and 32 Cygni during November and December 1961
Not Available
| A photometric system
Not Available
| The Transfer of the North Polar Standards to the Southern Hemisphere.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1953ApJ...117...83C&db_key=AST
| A Study of the Concentration of Early-Type Stars in Cygnus.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...114..492R&db_key=AST
| Red and Infrared Magnitudes for 125 Stars in Ten Areas
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...113..324K&db_key=AST
| Photoelectric Studies. I. Color-Luminosity Array for Members of the Hyades Cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1950ApJ...111...65E&db_key=AST
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kis Medve |
| Rektaszcenzió: | 03h40m54.06s |
| Deklináció: | +89°06'17.6" |
| Vizuális fényesség: | 8.11 |
| Távolság: | 88.106 parszek |
| RA sajátmozgás: | -50.9 |
| Dec sajátmozgás: | -31 |
| B-T magnitude: | 8.555 |
| V-T magnitude: | 8.147 |
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