תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
| Photometric survey near the main Galactic meridian: 2.1. Finding charts and photoelectric U,B,V,R stellar magnitudes in 25 fields
Finding charts and photoelectric U,B,V,R magnitudes of stars in 25fields in the Main Galactic Meridian (programme MEGA) are presented.This part of the photometric survey includes fields near the NorthGalactic pole and fields at southern Galactic latitudes. Together withthe finding charts of 2.5(deg) x2.5(deg) the equatorial coordinates ofthe stars are given for epoch and equinox 1950.
| Photometric Survey Near the Main Galactic Meridian - Part One - Photoelectric Stellar Magnitudes and Colours in the UBVR System
Not Available
| Strong-lined G dwarfs in the galactic disk
Using a quantitative, three-dimensional spectral classification systemdeveloped earlier (Rose 1984), a class of strong lined dwarf stars hasbeen identified in the Galactic disk. The strong-lined dwarfs were foundin a sample of G5-G7 stars with m(B) of about 11 classified as giants byUpgren (1962) in his North Galactic Pole survey. The misclassificationin luminosity on Upgren objective-prism spectra results from the greatstrength of the CN bands in these stars. The strong-lined stars aredetermined to be dwarfs from a measurement of the strength of Sr II 4077A relative to neighboring Fe I lines. Furthermore, these stars are foundto be strong lined in Fe and to have anomalous broadband colors thatsuggest heavy line blanketing. They have properties similar to starswith Fe/H abundance ratios + 0.25 in the Cayrel de Strobel and Bentolila(1983) Fe/H abundance catalog. The strong lined dwarfs contribute about25 percent of the G5-G7 dwarfs at m(B) of about 11 in the Upgren survey.However, there is a selection bias in favor of the strong-lined dwarfs,since they are hotter, and hence more luminous, than solar-abundancedwarfs of the same spectral type. When this selection effect isaccounted for, it is found that the strong lined stars comprise about 15percent of the Galactic disk.
| Red horizontal-branch stars in the galactic disk
A quantitative, three-dimensional spectral classification systemdeveloped by Rose (1984), which uses 2.5-A resolution spectra in theblue, has been used to identify a class of red horizontal branch (RHB)stars in the Galactic disk that are similar to those in the 'metal rich'globular cluster M 71. The RHB are denoted as evolved stars by their SrII 4077 line, and are distinguished from post-main sequence starsevolving through the same region of the HR diagram on the basis of theunique appearance of their CN 3883 and 4216 A bands. The RHB starsconsitute at least 5 percent of the entire giant branch population ofthe disk.
| MKJ and MSS classification of solar-type stars within 100 parsecs of the sun - Preliminary results
Not Available
| Spectral types and UBV photometry of G-K giants at the north galactic pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78...37S&db_key=AST
| Spectra of Upgren's unclassified stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..669S&db_key=AST
| Upgren's unclassified stars A: a new type of G-giant stars ?
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..334S&db_key=AST
| The space distribution of late type stars in a North galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67...37U&db_key=AST
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | כלבי ציד |
| התרוממות ימנית: | 12h09m16.22s |
| סירוב: | +42°28'54.2" |
| גודל גלוי: | 8.481 |
| מרחק: | 54.259 פארסק |
| תנועה נכונה: | -132.4 |
| תנועה נכונה: | -10.3 |
| B-T magnitude: | 9.311 |
| V-T magnitude: | 8.55 |
קטלוגים וכינוים:
|
INHABITED SKY
