目录
图像
上传图像
DSS Images Other Images
相关文章
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
| 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
| CCD photometry and astrometry of visual double and multiple stars of the HIPPARCOS Catalogue. II. CCD photometry and differential astrometry of 288 southern ``Intermediate'' systems
We present photometric and astrometric data of about 280 visual doublestars of the ``intermediate'' class, i.e. with angular separationsmainly in the range 2arcsec < rho < 12arcsec . The observationshave been obtained in 1991-92 with a CCD camera attached to the 91 cmDutch telescope at ESO La Silla, Chile. Differential magnitudes of thedouble star components as well as magnitudes and colour indices of theindividual components have been determined in the Cousins V and Ipassbands with an internal error of about 0.005 mag and an externalaccuracy of less than 0.03 mag. In addition, angular separations havebeen secured to an internal accuracy of 0.004arcsec and position anglesto about 0.05degr. Tables 1 to 4 are only available in electronic format the CDS via ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html. Based on observationscollected at the European Southern Observatory, La Silla, Chile.
| Speckle Interferometry at the US Naval Observatory. IV.
The results of 1314 speckle interferometric observations of 625 binarystars, ranging in separation from 0.2" to 5.2" with a limiting secondarymagnitude of V=11, are tabulated. These observations were obtained usingthe 66 cm refractor at the US Naval Observatory in Washington, DC, withan intensified CCD detector. This is the fourth in a series of paperspresenting measures obtained with this equipment and covers the period1997 January 1 through December 31. Random errors for all measures areestimated to be 18 mas in separation and 0.57d/rho in position angle,where rho is the separation in arcseconds.
| Speckle Interferometry at the US Naval Observatory. III.
Position angles and separations resulting from 2578 speckleinterferometric observations of 590 binary stars are tabulated. This isthe third in a series of papers presenting measures obtained using the66 cm refractor at the US Naval Observatory in Washington, DC, andcovers the period from 1995 June through 1996 December. Program starsrange in separation from 0.2" to 4.3", with a limiting magnitude ofV=11. Random errors are estimated to be 17.0 mas in separation and0.56d/rho in position angle, where rho is the separation in arcseconds.These are the first results acquired using an improved intensified CCDdetector. The new detector, in concert with an intensity-filteringtechnique applied in software, has permitted a 1 mag increase in dynamicrange, to 3.5 mag, for pairs separated by about 2". The instrumentationand calibration are briefly described, with an emphasis on thecharacteristics of the new detector. The software filter used toincrease the dynamic range is also described.
| Speckle Interferometry at the US Naval Observatory. II.
Position angles and separations resulting from 2406 speckleinterferometric observations of 547 binary stars are tabulated. This isthe second in a series of papers presenting measures obtained using the66 cm refractor at the US Naval Observatory in Washington, DC, with anintensified CCD detector. Program stars range in separation from 0.2" to3.8", with Deltam<=2.5 mag and a limiting magnitude of V=10.0. Theobservation epochs run from 1993 January through 1995 August. Randomerrors are estimated to be 14 mas in separation and 0.52d/rho inposition angle, where rho is the separation in arcseconds. Theinstrumentation and calibration are briefly described. Aspects of thedata analysis related to the avoidance of systematic errors are alsodiscussed.
| Mesures et decouvertes d'etoiles doubles effectuees a la lunette de 50cm de l'Observatoire de Nice. Measures and discoveries of visual double stars made with the 50cm refractor at the Nice Observatory.
Measures and discoveries of visual double stars made at the Observatoirede la Cote d'Azur at Nice, between 1988 and 1994, with the 50cmrefractor equipped with a filar micrometer and electronic recordingdevice. The programs proposed by J. Dommanget involve the complement ofthe C.C.D.M. (resolving problems of identification of double stars andof coherency in the Index) and the INput CAtalog Hipparcos (resolutionof ambiguities on the binarity and on the position of certain doublestars which have seldom or never been observed again from the epoch ortheir discovery). The author has discovered three new binaries: JCT1,JCT2 and JCT3.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| A preliminary compilation of DS-programme star positions
A catalog is presented of the double-star-program (DS-program) starpositions, listing right ascensions for 930 DSs and declinations for1225 DSs of the program. The positions were compiled from the observedvalues obtained between 1980 and 1987 with the meridian circles of sixUSSR observatories (the Moscow, Kazan', Kiev, Khar'kov, Odessa, andTashkent Observatories) and the Belgrade Observatory. The measurementsand the treatment of the observational material were performed using therelative method, and the FK-4 system stars were used as reference stars.
| Photographic observations of visual double stars
The results of photographic observations of 199 visual double stars,obtained at the Bosscha Observatory at Lembang, Indonesia, in the years1958-1975 (with one 1953 plate) are presented. The material comprises708 plates with an average of 37 images measured per plate. A shortdescription of the program is given (cf. van Albada-van Dien, 1958).
| Visual multiples. VII - MK classifications
Classifications are given for 865 components of visual multiples; theyshow no systematic differences from the MK system, and the random errorsare one subclass in type and two-thirds of a luminosity class. It isfound that at least 1% of the F-type IV and V stars are weak-lined, 32%of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and V starsare early-type Am. Attention is called to the large fraction (55%) ofthe A3-A9 III-V stars that are of luminosity classes III or IV, unlikethe percentage (16%) at neighboring types.
| Photographic observations of visual double stars
Mean positions, the corresponding epochs, relative separations, positionangles, and mean errors are presented for 95 pairs of visual doublestars, mostly in the Southern Hemisphere. The results were obtained bymeasuring plates taken with the 60-cm visual refractor of BosschaObservatory, Lembang, Indonesia, over a 16-yr period. The reductionmethod used in determining the mean positions, epochs, and errors isdiscussed.
| Micrometer measures of doubles stars. III.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963AJ.....68...57V&db_key=AST
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
