Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
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
| The Pul-3 catalogue of 58483 stars in the Tycho-2 system
A catalogue of positions and proper motions of 58483 stars (Pul-3) hasbeen constructed at the Pulkovo observatory. The Pul-3 is based on theresults of measurements of photographic plates with galaxies (Deutsch'splan). All plates were taken using the Pulkovo Normal Astrograph (thefirst epoch is in the 1950s and the second epoch is in the 1970s).The Pul-3 catalogue contains stars of mainly 12 to 16.5 mag in 146fields with galaxies in the declination zone from -5o to+85o. The Tycho-2 has been used as a reference catalogue.The mean epoch of the Pul-3 is 1963.25. The internal positional accuracyof the Pul-3 catalogue at the mean epoch of observations is ±80mas. The accuracy of the proper motions is mostly within ±3mas/yr to ±12 mas/yr. Comparisons of the Pul-3 with Tycho-2 andARIHIP have been done at the mean epoch of the Pul-3. The Pul-3 externalpositional accuracy relative to Tycho-2 is ±150 mas.The catalogue 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/418/357
| Binary Star Orbits. II. Preliminary First Orbits for 117 Systems
Orbital elements are presented for 117 binary systems with no previousorbit calculation. For nearly all of these systems, these elements mustbe regarded as preliminary, but the ephemerides presented here should berelatively accurate over the next several decades. Further, the analysisof these systems should highlight the need for their continuedobservation by dedicated programs to improve the veracity of theseelements.
| 10 New γ Doradus and δ Scuti Stars
We present high-resolution spectroscopy and precision photometry of fivenew γ Doradus and five new δ Scuti variables. The five newγ Doradus variables substantially increase the number of confirmedstars of this class. All 10 stars fall in the spectral class rangeF0-F2, but they are cleanly separated into two groups by theirluminosity and photometric periods. However, the period gap between theγ Doradus and δ Scuti stars is becoming very narrow since weconfirm that HD 155154 is a γ Doradus star with the shortestperiods reported to date (the shortest of its four periods is ~0.312days). We do not find any evidence in our sample for stars exhibitingboth δ Scuti- and γ Doradus-type pulsations.
| 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.
| Mesures d'etoiles doubles faites a Nice (5eme serie. Double star measurements made at Nice
We present the last observations from two lists: General program and MLRpairs, made with the 50~cm refractor of Nice Observatory.
| ICCD speckle observations of binary stars. 11: Measurements during 1991-1993 from the Kitt Peak 4 M telescope
One-thousand one-hundred ninety-seven observations of 730 binary starsystems, observed by means of speckle interferometry with the 4 mtelescope on Kitt Peak, are presented. Included in these binary starsare new interferometric companions to five visual binaries. Thesemeasurements, made mostly during the period 1991 to 1993, comprise the11th installment of results stemming from our speckle program at the 4 mclass telescopes on Kitt Peak, Cerro Tololo, and Mauna Kea.
| All-sky Stromgren photometry of speckle binary stars
All-sky Stromgren photometric observations were obtained for 303 specklebinaries. Most stars were in the range of V = 5-8. These data, whencombined with ratios of intensities from the CHARA speckle photometryprogram, will allow the determination of photometric indices for theindividual components of binary stars with separations as small as 0.05arcsec. These photometric indices will complement the stellar massesfrom the speckle interferometry observations to provide a much improvedmass-luminosity relationship.
| The 8190-A Sodium Doublet in Cataclysmic Variables - Part Two - too Cool for Comfort
In this paper we present the results of time-resolved spectroscopy inthe near-infrared of five cataclysmic variables: U Gem, SS Aur, BDPav, DO Dra and CN Ori. The spectral region observed was chosen tocover the Na 1 doublet at ?8190 Å which is strong inlate-type dwarfs. Radial-velocity curves were measured for thesecondary stars and values for Kabs determined for eachobject. For DO Dra an improved orbital period of 3.969±0.003 hrwas derived.U Gem and SS Aur showed significant apparent eccentricities of0.027±0.012 and 0.17±0.07, respectively. This distortionof the radial-velocity curve is probably caused by line quenching dueto irradiation of the secondary, or contamination of the spectrum byemission from the disc, or a combination of the two. For U Gem theapparent eccentricity was used to correct the observed Kabsfor these effects. Mass ranges were derived for all the objects. For U Gem, which has themost closely constrained result, the secondary mass is larger thanpredicted using main-sequence mass-period relations. Spectral-typeestimates for U Gem and DO Dra are also later than expected if thesecondary obeys an empirical main-sequence mass-radius relation. It isconcluded that the assumption of main-sequence status for thesecondary star should be used with caution.
| ICCD speckle observations of binary stars. IV - Measurements during 1986-1988 from the Kitt Peak 4 M telescope
One thousand five hundred and fifty measurements of 1006 binary starsystems observed mostly during 1986 through mid-1988 by means of speckleinterferometry with the KPNO 4-m telescope are presented. Twenty-onesystems are directly resolved for the first time, including newcomponents to the cool supergiant Alpha Her A and the Pleiades shellstar Pleione. A continuing survey of The Bright Star Catalogue yieldedeight new binaries from 293 bright stars observed. Corrections tospeckle measures from the GSU/CHARA ICCD speckle camera previouslypublished are presented and discussed.
| ICCD speckle observations of binary stars. II - Measurements during 1982-1985 from the Kitt Peak 4 M telescope
This paper represents the continuation of a systematic program of binarystar speckle interferometry initiated at the 4 m telescope on Kitt Peakin late 1975. Between 1975 and 1981, the observations were obtained witha photographic speckle camera, the data from which were reduced byoptical analog methods. In mid-1982, a new speckle camera employing anintensified charge-coupled device as the detector continued the programand necessitated the development of new digital procedures for reducingand analyzing speckle data. The camera and the data-processingtechniques are described herein. This paper presents 2780 newmeasurements of 1012 binary and multiple star systems, including thefirst direct resolution of 64 systems, for the interval 1982 through1985.
| Micrometer measurements of visual binaries
A total of 376 micrometer measurements of 116 visual binaries made atthe Nice Observatory, France, in the years 1980-1983 is presented. Eachpair is identified by the A.D.S. number, the name of the couple, and theB.D. number. The next line gives the I.D.S. number, the A.D.S.magnitudes, and the spectral types. This is followed by the epoch of theobservation, the observed position angle and distance of the components,and the aperture of the refractor used. The means and the residuals fromknown orbits are given in the next lines. The symbol 'N' denotes thatthe observations were made with a 74-cm refractor; the symbol 'n'denotes a 50-cm refractor.
| 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.
| 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
| Mikrometermessungen von Doppelsternen. VI.
Not Available
| Mesures d'étoiles doubles faites au 0,38 m de l'Observatoire de Paris.
Not Available
| Measures of double stars.
Not Available
| Mesures d'étoiles doubles faites au rĝfraceur de 38 cm de l'Observatoire de Nice
Not Available
| Mesures d'étoiles doubles faites à l'Observatoire de Paris
Not Available
| Mesures d'étoiles doubles faites à Stras bourg- dernière série
Not Available
| Mesures d'étoiles doubles faites à Strasbourg en 1952-1953
Not Available
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Ejderha |
| Sað Açýklýk: | 12h00m37.51s |
| Yükselim: | +69°11'07.7" |
| Görünürdeki Parlaklýk: | 7.408 |
| Uzaklýk: | 195.312 parsek |
| özdevim Sað Açýklýk: | -23 |
| özdevim Yükselim: | -8 |
| B-T magnitude: | 7.813 |
| V-T magnitude: | 7.442 |
Kataloglar ve belirtme:
|
