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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
| BVRIJHK Photometry of Cepheid Variables
Contemporaneous BVRI and JHK photometry are presented for twenty-twoCepheid variables. Nineteen of these variables also have uvby photometryavailable, making them excellent candidates for application of theInfrared Flux Method of distance determination. We are in the process ofacquiring high precision radial velocities of sixteen of these variablesin anticipation of conducting that analysi. (SECTION: Stars)
| UBV Photoelectric Photometry Catalogue (1986). III Errors and Problems on DM and HD Stars
Not Available
| Observational studies of Cepheids. I - BVRI photometry of bright Cepheids
Over 1,000 differentially determined photoelectric BVRI observations andthe resulting light curves are presented for 24 bright Cepheidsaccessible from Northern Hemisphere observatories. The internalprecision of these data is shown to be better than + or - 0.01 mag, andthe accuracy of transformation to the Johnson BVRI system is nearly asgood.
| A photometric investigation of RV Tauri and yellow semiregular variables
Results are presented for DDO and UBV photoelectric photometry of 52 RVTau and semiregular variables and candidates. CN abundances, effectivetemperatures, surface gravities, absolute visual magnitudes, and massestimates are derived in the framework of the spectroscopic groupingsproposed by Preston et al. (1963). The photometry suggests a furtherdivision of Preston's group A, and a possible physical connection isindicated between this group and the semiregular variables. Thespectroscopic groups are shown to be well separated in the DDOcolor-color diagrams when mean colors are used for individual stars. Anupper limit of about 3 solar masses is determined for stars in eachgroup. A correlation between derived iron abundances and published IRexcesses obtained from flux measurements at 3.6 and 11.3 microns isfound which supports the contention that dust production incircumstellar shells increases with increasing metallicity.
| Light and radial velocity observations of classical Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJS...32..399E&db_key=AST
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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Aquila |
| Ascensione retta: | 19h09m01.85s |
| Declinazione: | +01°21'09.3" |
| Magnitudine apparente: | 7.566 |
| Distanza: | 146.199 parsec |
| Moto proprio RA: | 44.8 |
| Moto proprio Dec: | 5 |
| B-T magnitude: | 8.098 |
| V-T magnitude: | 7.61 |
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