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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}
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| UBVRI photometry of FKSZ stars. IV
The paper presents UBVRI photometry, in the Kron-Cousins system, for 117stars of the Catalog of Fundamental Faint Stars in the declination zone+18-0 deg. The observations were performed from July 1988 to March 1990with the ESO 0.50-m telescope at the ESO in La Silla, Chile. The resultsof 24 nights of observations are reported.
| The detection of close binary systems in observations of lunar occultations with a 6-m telescope
The paper presents the results of photoelectric observations of thelunar occultation of 10 stars which were carried out with the 6-mtelescope of the Special Astrophysical Observatory of the USSR Academyof Sciences. The brightness strip distribution of the occulted source isrestored using a modified regularization method in which a prioriinformation on the nonnegativity of the solution is accounted for. Theupper limits to the angular diameters of eight stars are obtained. For astar with a brightness of 11.07 mag, an angular resolution of 0.0101 isachieved. The following close binary systems were detected: SAO 128720and SAO 110268.
| The search for close binary stars by the lunar-occultation method
The lunar occultations of 12 stars were observed with 48-cm and 6-mreflectors during 1980-1982. The data analysis was performed by thebrightness-distribution restoration method. Three close binaries werediscovered, and the angular resolution was estimated.
| Observations of Lunar Occultations of Stars with the 6-METER Telescope
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Osservazione e dati astrometrici
| Costellazione: | Pesci |
| Ascensione retta: | 02h00m12.73s |
| Declinazione: | +06°55'04.9" |
| Magnitudine apparente: | 7.459 |
| Distanza: | 354.61 parsec |
| Moto proprio RA: | -3.7 |
| Moto proprio Dec: | -16.3 |
| B-T magnitude: | 9.745 |
| V-T magnitude: | 7.648 |
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