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|Photometric and Coravel observations of red giant candidates in three open clusters: membership, binarity, reddening and metallicity|
Aims.We present new CORAVEL radial-velocity observations andphotoelectric photometry in the UBV and DDO systems for a sample ofpotential members of the red-giant branches of NGC 6192, NGC 6208 andNGC 6268, three open clusters projected close to the Galactic centerdirection. We also examine the properties of a sample of 42 inner diskopen clusters projected towards almost the same direction as the threeclusters. Methods: .Cluster members and red field giants werediscriminated by using the CORAVEL radial-velocity data and by applyingtwo photometric criteria. Interstellar reddening and metal content ofthe clusters were derived from combined BV and DDO data. Results:.Cluster membership for five red giants in NGC 6192, three in NGC 6208and three in NGC 6268 has been confirmed by the analysis of thephotometric and kinematic data. Photometric membership probabilitiesshow very good agreement with those obtained from CORAVEL radialvelocities. Three new spectroscopic binaries were discovered among thered giants of NGC 6192 and NGC 6208. Mean radial velocities and E(B-V)colour excesses were derived. Conclusions: .The overallmetallicities were found to be nearly solar for NGC 6208 and above solarfor NGC 6192 and NGC 6268. Most of the clusters located closer than 2kpc from the Sun in the considered direction are slightly more reddenedthan the absorption resulting from the Baade's window absorption law.
|Proper motion determination of open clusters based on the UCAC2 catalogue|
We present the kinematics of hundreds of open clusters, based on theUCAC2 Catalogue positions and proper motions. Membership probabilitieswere obtained for the stars in the cluster fields by applying astatistical method uses stellar proper motions. All open clusters withknown distance were investigated, and for 75 clusters this is the firstdetermination of the mean proper motion. The results, including the DSSimages of the cluster's fields with the kinematic members marked, areincorporated in the Open Clusters Catalogue supported on line by ourgroup.
|Astrophysical parameters of Galactic open clusters|
We present a catalogue of astrophysical data for 520 Galactic openclusters. These are the clusters for which at least three most probablemembers (18 on average) could be identified in the ASCC-2.5, a catalogueof stars based on the Tycho-2 observations from the Hipparcos mission.We applied homogeneous methods and algorithms to determine angular sizesof cluster cores and coronae, heliocentric distances, mean propermotions, mean radial velocities, and ages. For the first time we derivedistances for 200 clusters, radial velocities for 94 clusters, and agesof 196 clusters. This homogeneous new parameter set is compared withearlier determinations, where we find, in particular, that the angularsizes were systematically underestimated in the literature.
|Probable binary open star clusters in the Galaxy.|
The existence of double/binary clusters in the Magellanic Clouds isfairly well established, whereas only one such pair, h + χ Persei,is known in the Galaxy. From the catalogues of open clusters of theGalaxy, we have identified 18 probable pairs of clusters (with knowndistances), with spatial separations less than 20pc. The tidaldisruption timescales for these pairs, due to Galactic differentialrotation are calculated, using cluster data where available or byassuming typical values. In some cases, these timescales are larger thanthe average open cluster lifetime, =~10^8^yr. About 8% of open clustersappear to be members of binary systems, and hence binary cluster systemsmay not be very uncommon in the Galaxy.
|The Sagittarius-Carina Arm Structure and Parameters of Spiral Pattern|
|Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters|
|Variable stars in open clusters.|
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