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The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/941
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| uvby Hβ CCD photometry and membership segregation of the open cluster NGC 2548; gaps in the Main Sequence of open clusters
Deep CCD photometry in the uvby-Hβ intermediate-bandsystem is presented for the cluster NGC 2548 (M 48). A completemembership analysis based on astrometric and photometric criteria isapplied. The photometric analysis of a selected sample of stars yields areddening value of E(b-y)= 0.06±0.03, a distance modulus ofV_0-M_V= 9.3±0.5 (725 pc) and a metallicity of [ Fe/H] = - 0.24±0.27. Through isochrone fitting we find an age of log t = 8.6±0.1 (400 Myr). Our optical photometry and JHK from 2MASS arecombined to derive effective temperatures of cluster member stars. Theeffective temperature distribution along the main sequence of thecluster shows several gaps. A test to study the significance of thesegaps in the main sequence of the HR diagram has been applied. The methodis also applied to several other open clusters (Pleiades, Hyades, NGC1817 and M 67) to construct a sequence of metallicities and ages. Thecomparison of the results of each cluster gives four gaps with highsignificance (one of them, centred at 4900 K, has not been previouslyreported).
| 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
| Determination of proper motions and membership of the open star cluster NGC 2548
Absolute proper motions, their corresponding errors and membershipprobabilities of 501 stars in the intermediate-age open cluster NGC 2548region are determined from MAMA measurements of 10 photographic plates.The plates have the maximum epoch difference of 82 years and they weretaken with the double astrograph at Zô-Sèstation ofShanghai Observatory, which has an aperture of 40 cm and a plate scaleof 30 arcsec mm-1. The average proper motion precision is1.18 mas yr-1. These proper motions are used to determine themembership probabilities of stars in the region. The number of starswith membership probabilities higher than 0.7 is 165. Table 5 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/ A+A/381/464, and by e-mail requestto Lola.Balaguer@am.ub.es MAMA (Machine Automatique àMesurer pourl'Astronomie, http://dsmama.obspm.fr) is developed and operated byINSU/CNRS and Observatoire de Paris.
| Kinematics of Hipparcos Visual Binaries. II. Stars with Ground-Based Orbital Solutions
This paper continues kinematical investigations of the Hipparcos visualbinaries with known orbits. A sample, consisting of 804 binary systemswith orbital elements determined from ground-based observations, isselected. The mean relative error of their parallaxes is about 12% andthe mean relative error of proper motions is about 4%. However, even 41%of the sample stars lack radial velocity measurements. The computedGalactic velocity components and other kinematical parameters are usedto divide the stars with known radial velocities into kinematical agegroups. The majority (92%) of binaries from the sample are thin diskstars, 7.6% have thick disk kinematics and only two binaries have halokinematics. Among them, the long-period variable Mira Ceti has a verydiscordant {Hipparcos} and ground-based parallax values. From the wholesample, 60 stars are ascribed to the thick disk and halo population.There is an urgent need to increase the number of the identified halobinaries with known orbits and substantially improve the situation withradial velocity data for stars with known orbits.
| ICCD Speckle Observations of Binary Stars. XXIII. Measurements during 1982-1997 from Six Telescopes, with 14 New Orbits
We present 2017 observations of 1286 binary stars, observed by means ofspeckle interferometry using six telescopes over a 15 year period from1982 April to 1997 June. These measurements constitute the 23dinstallment in CHARA's speckle program at 2 to 4 m class telescopes andinclude the second major collection of measurements from the MountWilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are alsopresented for 14 systems, seven of which have had no previouslypublished orbital analyses.
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Radial velocities, rotations, and duplicity of a sample of early F-type dwarfs
We present new radial and rotational velocities for 595 nearby early Fdwarfs, based on digital spectra cross-correlated with individuallyoptimised synthetic template spectra. The selection of optimumtemplates, the determination of rotational velocities, and theextraction of velocities from the blended spectra of double-linedspectroscopic binaries are discussed in some detail. We find 170spectroscopic binaries in the sample and determine orbits for 18double-lined and 2 single-lined binaries, including some spectroscopictriples. 73 stars are listed with too rapid rotation to yield usefulradial velocities (i.e. v sin i > 120 km~s^-1). We discuss the binaryfrequency in the sample, and the influence of unrecognised binaries onthe definition of clean metallicity groups of young F dwarfs and thedetermination of their kinematical properties. Tables 1, 5 and 6 areonly available, and Tables 2-4 also available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html.
| Observations of Double Stars and New Pairs. XVII.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..105..475H&db_key=AST
| Radial Velocities of Binary and Proper-Motion Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981ApJS...46..247H&db_key=AST
| Orbits of 15 visual binaries.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...37...71H&db_key=AST
| Measures of southern visual double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..588H&db_key=AST
| Correction of the dynamical elements of the orbits of eleven visual binaries.
Not Available
| Micrometer observations of double stars.8.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJS...29..315H&db_key=AST
| On the inclination of rotation axes in visual binaries.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJ...190..331W&db_key=AST
| Micrometer measures of 401 double stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..878W&db_key=AST
| Mesures d'étoiles doubles faites au réfracteur de 38 cm de l'Observatoire de Nice
Not Available
| Masses, luminosities, colors, and space motions of 228 visual binaries
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965AJ.....70...19E&db_key=AST
| Mesures d'étoiles doubles faites au 0,38 m de l'Observatoire de Paris.
Not Available
| Mesures d'étoiles doubles faites au réfracteur de 38 cm de l'Observatoire de Nice
Not Available
| Eléments orbitaux de vingt étoiles doubles
Not Available
| Mesures d'étoiles doubles faites à l'Observatoire du Pic-du-Midi en février-mars 1956
Not Available
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Miembro de los siguientes grupos:
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Datos observacionales y astrométricos
| Constelación: | Hidra |
| Ascensión Recta: | 08h17m15.69s |
| Declinación: | -05°22'08.7" |
| Magnitud Aparente: | 7.781 |
| Distancia: | 110.742 parsecs |
| Movimiento Propio en Ascensión Recta: | -26.1 |
| Movimiento Propio en Declinación: | 30.4 |
| B-T magnitude: | 8.235 |
| V-T magnitude: | 7.819 |
Catálogos y designaciones:
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