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Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants
We present the parameters of 891 stars, mostly clump giants, includingatmospheric parameters, distances, absolute magnitudes, spatialvelocities, galactic orbits and ages. One part of this sample consistsof local giants, within 100 pc, with atmospheric parameters eitherestimated from our spectroscopic observations at high resolution andhigh signal-to-noise ratio, or retrieved from the literature. The otherpart of the sample includes 523 distant stars, spanning distances up to1 kpc in the direction of the North Galactic Pole, for which we haveestimated atmospheric parameters from high resolution but lowsignal-to-noise Echelle spectra. This new sample is kinematicallyunbiased, with well-defined boundaries in magnitude and colours. Werevisit the basic properties of the Galactic thin disk as traced byclump giants. We find the metallicity distribution to be different fromthat of dwarfs, with fewer metal-rich stars. We find evidence for avertical metallicity gradient of -0.31 dex kpc-1 and for atransition at ~4-5 Gyr in both the metallicity and velocities. Theage-metallicity relation (AMR), which exhibits a very low dispersion,increases smoothly from 10 to 4 Gyr, with a steeper increase for youngerstars. The age-velocity relation (AVR) is characterized by thesaturation of the V and W dispersions at 5 Gyr, and continuous heatingin U.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| High-precision effective temperatures of 215 FGK giants from line-depth ratios
We present precise effective temperatures (Teff) of 215 FGKgiants determined using the method of line-depth ratios. For each star,we have measured the line depths and equivalent widths of a large numberof spectral lines of low and high excitation potentials and established~100 relations between Teff and their ratios. Starting withan initial value Teff, the relations are then self-calibratedby an iterative process. Our final estimates have been compared withvery accurate (1 per cent) published temperatures and show a goodagreement. Using our calibrations, we derive precise temperatures for215 giants with near-solar metallicity, from high-resolution (R = 42000)and high signal-to-noise ratio (S/N = 100-250) echelle spectra, obtainedwith the ELODIE spectrometer at the Observatoire de Haute Provence(OHP). The range of application of the method is 3500-5700K(G0III-K4III). The internal error for a single calibration is less than95K, while the combination of all 100 calibrations reduces theuncertainty to only 5-20K (1?). A big advantage of the line ratiomethod is its independence of interstellar reddening, and its modestsensitivity to spectral resolution, abundance, macroturbulence and otherfactors.
| Determinations of high-precision effective temperatures for giants based on spectroscopic criteria
Spectral lines with high and low excitation potentials responddifferently to changes of the effective temperature (T eff), making theratio of their depths (or equivalent widths) a very sensitivetemperature indicator. We derive a set of 100 equations relating T effto the line-depth ratios, calibrated against accurate (to within 1%)published temperature determinations for giants. These relations areused to determine very accurate temperatures for a sample of 110 giantswith nearly solar metallicities based on high-resolution (R = 42 000)échelle spectra with high signal-to-noise ratios (SNRs). Thecalibration relations are valid for temperatures of 4000 7000 K (F2IIIK4III). The internal errors of each of the calibration relations arebelow 95 K, and applying all these relations together to spectra withSNR = 100 reduces the errors to 5 25 K (1 ?). A major advantage ofthis technique is that it is independent from interstellar reddening,spectroscopic resolution, and line broadening due to rotation andmicroturbulence.
| Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
The availability of the Hipparcos Catalogue has triggered many kinematicand dynamical studies of the solar neighbourhood. Nevertheless, thosestudies generally lacked the third component of the space velocities,i.e., the radial velocities. This work presents the kinematic analysisof 5952 K and 739 M giants in the solar neighbourhood which includes forthe first time radial velocity data from a large survey performed withthe CORAVEL spectrovelocimeter. It also uses proper motions from theTycho-2 catalogue, which are expected to be more accurate than theHipparcos ones. An important by-product of this study is the observedfraction of only 5.7% of spectroscopic binaries among M giants ascompared to 13.7% for K giants. After excluding the binaries for whichno center-of-mass velocity could be estimated, 5311 K and 719 M giantsremain in the final sample. The UV-plane constructed from these datafor the stars with precise parallaxes (σπ/π≤20%) reveals a rich small-scale structure, with several clumpscorresponding to the Hercules stream, the Sirius moving group, and theHyades and Pleiades superclusters. A maximum-likelihood method, based ona Bayesian approach, has been applied to the data, in order to make fulluse of all the available stars (not only those with precise parallaxes)and to derive the kinematic properties of these subgroups. Isochrones inthe Hertzsprung-Russell diagram reveal a very wide range of ages forstars belonging to these groups. These groups are most probably relatedto the dynamical perturbation by transient spiral waves (as recentlymodelled by De Simone et al. \cite{Simone2004}) rather than to clusterremnants. A possible explanation for the presence of younggroup/clusters in the same area of the UV-plane is that they have beenput there by the spiral wave associated with their formation, while thekinematics of the older stars of our sample has also been disturbed bythe same wave. The emerging picture is thus one of dynamical streamspervading the solar neighbourhood and travelling in the Galaxy withsimilar space velocities. The term dynamical stream is more appropriatethan the traditional term supercluster since it involves stars ofdifferent ages, not born at the same place nor at the same time. Theposition of those streams in the UV-plane is responsible for the vertexdeviation of 16.2o ± 5.6o for the wholesample. Our study suggests that the vertex deviation for youngerpopulations could have the same dynamical origin. The underlyingvelocity ellipsoid, extracted by the maximum-likelihood method afterremoval of the streams, is not centered on the value commonly acceptedfor the radial antisolar motion: it is centered on < U > =-2.78±1.07 km s-1. However, the full data set(including the various streams) does yield the usual value for theradial solar motion, when properly accounting for the biases inherent tothis kind of analysis (namely, < U > = -10.25±0.15 kms-1). This discrepancy clearly raises the essential questionof how to derive the solar motion in the presence of dynamicalperturbations altering the kinematics of the solar neighbourhood: doesthere exist in the solar neighbourhood a subset of stars having no netradial motion which can be used as a reference against which to measurethe solar motion?Based on observations performed at the Swiss 1m-telescope at OHP,France, and on data from the ESA Hipparcos astrometry satellite.Full Table \ref{taba1} is 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/430/165}
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| CA II H and K measurements made at Mount Wilson Observatory, 1966-1983
Summaries are presented of the photoelectric measurements of stellar CaII H and K line intensity made at Mount Wilson Observatory during theyears 1966-1983. These results are derived from 65,263 individualobservations of 1296 stars. For each star, for each observing season,the maximum, minimum, mean, and variation of the instrumental H and Kindex 'S' are given, as well as a measurement of the accuracy ofobservation. A total of 3110 seasonal summaries are reported. Factorswhich affect the ability to detect stellar activity variations andaccurately measure their amplitudes, such as the accuracy of the H and Kmeasurements and scattered light contamination, are discussed. Relationsare given which facilitate intercomparison of 'S' values with residualintensities derived from ordinary spectrophotometry, and for convertingmeasurements to absolute fluxes.
| The rotation velocities and metallicities of dwarf stars in the solar neighborhood
The rotation velocities (or upper limits) of 260 dwarfs from the Gliese(1969) catalog are determined using a photoelectric radial velocityscanner. The dependence of the correlation dip equivalent width (thestrength of metal lines) on the color (B-V) and metallicity is examined.Given the color and equivalent width, the method can determine the Fe/Habundance ratio with an accuracy up to 0.2.
| Radial Velocities of K-Dwarfs and M-Dwarfs
Not Available
| A survey of chromospheric CA II H and K emission in field stars of the solar neighborhood
Fluxes in 1 A bands at the centers of the H and K lines are beingmeasured in main-sequence F-G-K-M stars in the northern half of theWoolley et al. (1970) 'Catalog of stars within twenty-five parsecs ofthe sun', in a survey not yet completed. Results for 486 stars arepresented in the form of flux-color diagrams and discussed in light ofevidence that chromospheric activity declines with age in main-sequencestars. Support is noted for the reality of the Sirius moving group. Therelative numbers of more-active (Hyades-like) and less-active(solar-like) F-G stars are tolerably in agreement with a nearly constantrate of formation, but there exists an apparent deficiency in the numberof F-G stars exhibiting intermediate activity. The possibility that thegap is an accidental characteristic of the sample will be investigatedby extending the survey to southern declinations and greater distances.
| Yerkes actinometry. Zone +73deg to +90deg.
Not Available
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kis Medve |
| Rektaszcenzió: | 16h00m36.68s |
| Deklináció: | +80°37'40.1" |
| Vizuális fényesség: | 7.554 |
| Távolság: | 161.812 parszek |
| RA sajátmozgás: | -14.9 |
| Dec sajátmozgás: | 24.9 |
| B-T magnitude: | 8.898 |
| V-T magnitude: | 7.665 |
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