תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
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
| BVRI photometry and light curve analysis of VW CEP
Synthetic light curve solutions for the W UMa-system VW Cep have beendetermined by applying the most new version of Wilson (1998) approach toB-observations of 1996 and VRI-observations of 1999. From aconsideration of the possible evolution of this system, it is found thatthe system is a partial eclipsing contact one, and its primary to be anearly Main-Sequence F5 star of mass 0.85 Msolar and thesecondary to be a dwarf of spectral type G0 of mass 0.34Msolar.
| Not Available
Not Available
| Period study of the contact system VW Cep
New photoelectric U,B and V observations of the eclipsing contact systemVW Cep were taken in 1998-2000 and 23 new minima times were determined.The (O-C) diagram constructed using photographic and photoelectricminima times can be explained by the light-time effect caused by thepresence of a third and fourth body in the system and the long-termperiod decrease interpreted by the mass transfer from the more to theless massive component or/and the magnetic-braking process. The suddenperiod increase detected in 1999 is probably a consequence of theepisodic mass transfer from the less to the more massive component.Enhanced surface activity causes short-term apparent variations of theorbital period. The differences of times of the subsequent primary andsecondary minima show two significant periodicities P_1 = 2.94 +/- 0.07years and P_2 = 2.36 +/- 0.05 years. The latter periodicity is probablythe beat period of the orbital and rotational period at the latitudes ofmost frequent occurrence of the spots.
| New Photoelectric Light Curves of VW Cephei
Not Available
| 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.
| Photometric Observations of VW Cephei in 1996
Moments of minima and the lightcurve characteristics of VW Cephei aregiven.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Photoelectric Observations of the Close Eclipsing Binary VW Cephei
Not Available
| Photoelectric Photometry of VW Cephei in 1993
Not Available
| Photoelectric y and lambda6585 Observations of VW Cephei
Not Available
| Osservazioni fotoelettriche e determinazione del periodo della variabile ad eclisse VW Cephei
Not Available
| The Light-curves of Eclipsing Binaries
Not Available
| Photoelectric Observations of VW Cephei
Not Available
| 3 W UMa-type binaries with changing periods.
Not Available
| Photographic magnitudes of stars brighter than 7m.75 between +75° and +80° declination (Errata: 11 270)
Not Available
| Yerkes actinometry. Zone +73deg to +90deg.
Not Available
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | קפיאוס |
| התרוממות ימנית: | 20h38m05.09s |
| סירוב: | +76°49'59.4" |
| גודל גלוי: | 7.07 |
| מרחק: | 131.062 פארסק |
| תנועה נכונה: | 24.3 |
| תנועה נכונה: | 64.3 |
| B-T magnitude: | 7.53 |
| V-T magnitude: | 7.108 |
קטלוגים וכינוים:
|
