CCD photometric search for peculiar stars in open clusters. VII. Berkeley 11, Berkeley 94, Haffner 15, Lyngå 1, NGC 6031, NGC 6405, NGC 6834 and Ruprecht 130
Aims.The detection of magnetic chemically peculiar (CP2) stars in openclusters of the Milky Way can be used to study the influence ofdifferent galactic environments on the (non-)presence of peculiarities,which has to be taken into account in stellar evolution models.Furthermore it is still unknown if the CP2 phenomenon evolves, i.e. doesthe strength of the peculiarity feature at 5200 Å increase ordecrease with age. Methods: .We have observed eight young tointermediate age open clusters in the Δ a photometric system. Thisintermediate band photometric system samples the depth of the 5200Å flux depression by comparing the flux at the center with theadjacent regions having bandwidths of 110 Å to 230 Å. TheΔ a photometric system is most suitable to detect CP2 stars withhigh efficiency, but is also capable of detecting a small percentage ofnon-magnetic CP objects. Also, the groups of (metal-weak) λBootis, as well as classical Be/shell stars, can be successfullyinvestigated. This photometric system allows one to determine the age,reddening and distance modulus by fitting isochrones. Results:.Among the presented sample of eight galactic clusters, we have detectedtwenty three CP2, eight Be/Ae and eight metal-weak stars. Another sixobjects show a peculiar behaviour which is most probably due to anon-membership, variability or duplicity. Fitting isochrones to Δa photometry yields estimates of the age, reddening and distance thatare in excellent agreement with published values.
|
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.
|
A deep Hα survey of the Milky Way. VI. The l = 332° area
The Galactic plane has been observed between l= 330° to l= 336°as part of a velocity resolved Hα survey of the southern Milky Wayusing a scaning Fabry-Perot on a 36 cm telescope. The detailed analysisof the resultant Hα profiles reveals the presence of severallayers of ionized gas with different velocities over the surveyedregion. We have studied in detail both the 2-D spatial and velocitystructure of the HII regions RCW102, RCW104 and RCW106. Combining theseHα observations with stellar and radio data we provide estimatesfor the most probable distances of these different layers. The firstlayer at -5 km s-1 is local emission linked to the Sco-Cenassociation at 170 pc. The next layer, around -24 km s-1, isat 1.9 kpc and traces the near section of the Sagittarius-Carina arm.Well connected to the Sagittarius-Carina arm portions traced in theadjacent regions (l= 328° and l= 338° area), the arm, in thislongitude range, clearly shows and confirms the departure from alogarithmic spiral. The Scutum-Crux arm is also traced in this area byfaint and diffuse emission at -40 km s-1 which can be placedat 3.2 kpc. The layer at -52 km s-1 is the major spiral-armfeature of the studied area; its most probable stellar distance is 4.2kpc. An important emission component is also observed at -65 kms-1 in the southern part of the surveyed area. This mainlypatchy and filamentary emission we identify as the possible opticalcounterpart of a supernovae remnant centered at l= 332.0°,b=-3.2°. Finally, two complexes have been determined around 12.5 kpcwhich places them in the far section of the Norma arm.Based on observations collected at the European Southern Observatory.Table \ref{tab1} is only available in electronic form athttp://www.edpsciences.org
|
Deepsky delights.
Not Available
|
Ages and metallicities of star clusters: New calibrations and diagnostic diagrams from visible integrated spectra
We present homogeneous scales of ages and metallicities for starclusters from very young objects, through intermediate-age ones up tothe oldest known clusters. All the selected clusters have integratedspectra in the visible range, as well as reliable determinations oftheir ages and metallicities. From these spectra equivalent widths (EWs)of K Ca II, G band (CH) and Mg I metallic, and Hδ, Hγ andHβ Balmer lines have been measured homogeneously. The analysis ofthese EWs shows that the EW sums of the metallic and Balmer H lines,separately, are good indicators of cluster age for objects younger than10 Gyr, and that the former is also sensitive to cluster metallicity forages greater than 10 Gyr. We propose an iterative procedure forestimating cluster ages by employing two new diagnostic diagrams and agecalibrations based on the above EW sums. For clusters older than 10 Gyr,we also provide a calibration to derive their overall metal contents.
|
Proper Motions of Open Star Clusters and the Rotation Rate of the Galaxy
The mean proper motions of 167 Galactic open clusters withradial-velocity measurements are computed from the data of the Tycho-2catalog using kinematic and photometric cluster membership criteria. Theresulting catalog is compared to the results of other studies. The newproper motions are used to infer the Galactic rotation rate at the solarcircle, which is found to be ω0=+24.6±0.8 km s-1 kpc-1.Analysis of the dependence of the dispersion of ω0 estimates onheliocentric velocity showed that even the proper motions of clusterswith distances r>3 kpc contain enough useful information to be usedin kinematic studies demonstrating that the determination of propermotions is quite justified even for very distant clusters.
|
Integrated spectral evolution of Galactic open clusters
We present a library of 47 open-cluster integrated spectra, mostlyobtained at CASLEO (San Juan, Argentina) in the range 3600 < λ< 7400 Å, which are made available at CDS. The data arecombined with previous spectra to obtain 10 high signal-to-noise ratiobasic templates in the young and intermediate-age domains, which arealso provided in the library. These Galactic disc templates representthe increased time resolution spectral evolution of a stellar populationunit around the Solar metallicity level. The improved signal-to-noiseratio of the present templates with respect to previous template lists,together with their increased time resolution, allowed us to improve thefundamental parameters of some open clusters. The present spectrallibrary will be useful for several astrophysical applications,particularly for population syntheses of star-forming giant galaxies.
|
Proper motions of open clusters based on the TYCHO2 Catalogue. II. Clusters farther than 1 kpc
We determined the mean absolute proper motion of 94 open clusterssituated farther than 1 kpc from the Sun. The results are derived fromthe stellar proper motion data given in the Tycho2 Catalogue. The meanproper motion of the clusters and membership probability of individualstars were obtained from the proper motion data by applying thestatistical method proposed by Sanders (\cite{Sanders1971}). Themeasurements made use of a large number of stars, usually several tens,for each cluster. The total number of stars investigated in the fieldsof the clusters is 4864 of which 2021 were considered members. For 55clusters, this is the first determination of the proper motion. Based onobservations of the ESA Hipparcos satellite. Tables 1 to 95 are onlyavailable 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/qcat?J/A+A/388/168
|
Integrated photometric characteristics of galactic open star clusters
Integrated UBVRI photometric parameters of 140 galactic open clustershave been computed. Integrated I(V-R)0 and I(V-I)0colours as well as integrated parameters for 71 star clusters have beenobtained for the first time. These, in combination with published data,altogether 352 objects, are used to study the integrated photometriccharacteristics of the galactic open clusters. The I(MV)values range from -9.0 to -1.0 mag corresponding to a range in totalmass of the star clusters from ~ 25 to 4*E4 Msun.The integrated colours have a relatively narrow range, e.g., I(B-V){_0}varies from -0.4 to 1.2 mag. The scatter in integrated colours at agiven integrated magnitude can be understood in terms of differences infraction of red giants/supergiants in the clusters. The observedintegrated magnitudes and colours agree with the synthetic ones, exceptthe dependences of I(V-R)0 and I(V-I)0 colours forclusters younger than ~ 100 Myrs and also of the integrated magnitudesof oldest clusters. The large sample provides the most accurate agedependence of integrated magnitudes and colours determined so far. Theluminosity function of the I(MV) has a peak around -3.5 magand its slope indicates that only ~ 1% of the open clusters in thegalactic disc are brighter than I(MV)=-11 mag. No variationhas been found of integrated magnitude with galactocentric distance andmetallicity.
|
Fundamental parameters of the moderately young open clusters NGC 5999, NGC 6031, Ruprecht 115 and Ruprecht 120
We present CCD BVI Johnson-Cousins photometry for the southern openclusters NGC 5999, NGC 6031, Ruprecht 115 and Ruprecht 120. The sampleconsists of about 1160 stars reaching down to V ~ 19 mag. From theanalysis of the colour-magnitude diagrams, we confirm the reality of theclusters and derive their fundamental parameters (reddening, distanceand age). We also present integrated spectra for NGC 6031, Ruprecht 115and Ruprecht 120, covering a range from 3500 to 9200 A. From theequivalent widths of Balmer and infrared Ca ii triplet lines, as well asfrom a comparison of the obtained spectra with those of templateclusters, we derive reddening, age and metallicity. The photometric andspectroscopic results allow us to conclude that the four clusters aremoderately young (age &sim 100-500 Myr) and are locatedapproximately towards the Galactic Centre at ~ 2.3 kpc from the Sun. NGC6031 and Ruprecht 120 have nearly solar metal content, while Ruprecht115 appears to be slightly metal-rich.
|
Catalogue of blue stragglers in open clusters.
An extensive survey of blue straggler candidates in galactic openclusters of both hemispheres is presented. The blue stragglers wereselected considering their positions in the cluster colour-magnitudediagrams.They were categorized according to the accuracy of thephotometric measurements and membership probabilities. An amount of 959blue straggler candidates in 390 open clusters of all ages wereidentified and classified. A set of basic data is given for everycluster and blue straggler. The information is arranged in the form of acatalogue. Blue stragglers are found in clusters of all ages. Thepercentage of clusters with blue stragglers generally grows with age andrichness of the clusters. The mean ratio of the number of bluestragglers to the number of cluster main sequence stars is approximatelyconstant up to a cluster age of about 10^8.6^ yr and rises for olderclusters. In general, the blue stragglers show a remarkable degree ofcentral concentration.
|
Component Analysis of Open Clusters
Not Available
|
Catalogue of UBV Photometry and MK Spectral Types in Open Clusters (Third Edition)
Not Available
|
Investigation of the initial mass spectrum of open star clusters
The mass spectra of 228 open star clusters were derived by comparison ofcolor-magnitude diagrams with evolutionary tracks. The application tobinary stars showed the reliability of the mass determination. Thederived mass spectra were fitted by power laws as well as exponentiallaws. It could be shown that both approximate the mass spectra of openstar clusters on the same average significance level. The presentinvestigation revealed a correlation of the slope of the mass spectrawith the cluster age, whereas a detected correlation of the slope withgalactocentric distance is slight. The results suggest that the slope ofthe mass spectrum increases with increasing cluster and galactocentricdistance. These findings are discussed with respect to their reasons andprevious results concerning open clusters and field stars.
|
Integrated Photometric Parameters of Open and Globular Clusters
Not Available
|
Open clusters and galactic structure
A total of 610 references to 434 clusters are employed in thecompilation of a catalog of open clusters with color-magnitude diagramson the UBV or RGU systems. Estimates of reddening, distance modulus, ageand number of cluster members are included. Although the sample isconsidered representative of the discoverable clusters in the galaxy,the observed distribution is nonuniform because of interstellarobscuration. Cluster distribution in the galactic plane is found to bedominated by the locations of dust clouds rather than by spiralstructure. The distributions of clusters as a function of age andrichness class show that the lifetimes of poor clusters are much shorterthan rich ones, and that clusters in the outer disk survive longer thanthose in the inner disk. An outer disk age which is only about 50% theage of the globular clusters is indicated by cluster statistics. Thethickening of the galactic disk with increasing galactocentric distancemay be due to either a younger dynamical age or a lower gravitationalpotential in the outer regions.
|
Photographic Photometry of the Open Clusters NGC2910 NGC2925 RU79 and RU82 in Vela-II and NGC6031 in Norma-Ii
Abstract image available at:http://adsabs.harvard.edu/abs/1981A&AS...45..111T
|
Catalogue of Masses and Ages of Stars in 68 Open Clusters
Not Available
|
A catalogue of galactic clusters observed in three colours
This catalogue contains photometric data for 190 galactic clusters, allobserved in UBV or RGU. The distances of the young clusters (with spless than b3) have been calculated or recalculated according to method Aof Becker (1963). The galactic distribution of these clusters confirmstheir role of being good spiral tracers.
|
Southern open star clusters VI. UBV-Hbeta photometry of 18 clusters from Centaurus to Sagittarius.
Abstract image available at:http://adsabs.harvard.edu/abs/1975A&AS...20..155M
|
Uniform survey of clusters in the southern Milky Way.
Abstract image available at:http://adsabs.harvard.edu/abs/1975AJ.....80...11V
|
A Photometric Search for Distant OB Stars in Norma and an Investigation of the Norma Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1970A&A.....5..431S
|
An atlas of open cluster colour-magnitude diagrams
Not Available
|
The ages of open clusters
Not Available
|
The open cluster NGC 6031
Not Available
|
