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Photometric study of distant open clusters in the second quadrant: NGC 7245, King 9, King 13 and IC 166
We present a UBV CCD photometric study of four open clusters, NGC 7245,King 9, IC 166 and King 13, located between l = 90° and 135°.All are embedded in a rich Galactic field. NGC 7245 and King 9 are closetogether in the sky and have similar reddenings. The distances and agesare: NGC 7245, 3.8 +/- 0.35 kpc and 400 Myr; King 9 (the most distantcluster in this quadrant), 7.9 +/- 1.1 kpc and 3.0 Gyr. King 13 is 3.1+/- 0.3 kpc distant and 300 Myr old. King 9 and IC 166 (4.8 +/- 0.5 kpcdistant and 1 Gyr old) may be metal-poor clusters (Z = 0.008), asestimated from isochrone fitting. The average value of the distance ofyoung clusters from the Galactic plane in the above longitude range andbeyond 2 kpc (-47 +/- 16 pc, for 64 clusters) indicates that the youngdisc bends towards the southern latitudes.
| New catalogue of blue stragglers in open clusters
We present a catalogue of blue-straggler candidates in galactic openclusters. It is based on the inspection of the colour-magnitude diagramsof the clusters, and it updates and supersedesthe first version(Ahumada & Lapasset 1995). A new bibliographical search was made foreach cluster, and the resulting information is organised into twotables. Some methodological aspects have been revised, in particularthose concerning the delimitation of the area in the diagrams where thestragglers are selected.A total of 1887 blue-straggler candidates have been found in 427 openclusters of all ages, doubling the original number. The catalogued starsare classified into two categories mainly according to membershipinformation.The whole catalogue (Tables 8, 9, notes, and references) is 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/463/789
| Kinematics of the Open Cluster System in the Galaxy
Absolute proper motions and radial velocities of 202 open clusters inthe solar neighborhood, which can be used as tracers of the Galacticdisk, are used to investigate the kinematics of the Galaxy in the solarvicinity, including the mean heliocentric velocity components(u1,u2,u3) of the open cluster system,the characteristic velocity dispersions(σ1,σ2,σ3), Oortconstants (A,B) and the large-scale radial motion parameters (C,D) ofthe Galaxy. The results derived from the observational data of propermotions and radial velocities of a subgroup of 117 thin disk young openclusters by means of a maximum likelihood algorithm are:(u1,u2,u3) =(-16.1+/-1.0,-7.9+/-1.4,-10.4+/-1.5) km s-1,(σ1,σ2,σ3) =(17.0+/-0.7,12.2+/-0.9,8.0+/-1.3) km s-1,(A,B) =(14.8+/-1.0,-13.0+/-2.7) km s-1 kpc-1, and (C,D) =(1.5+/-0.7,-1.2+/-1.5) km s-1 k pc-1. A discussionon the results and comparisons with what was obtained by other authorsis given.
| 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.
| Morphological analysis of open clusters' propertiesII. Relationships projected onto the galactic plane
A morphological analysis study of open clusters' properties has beenachieved for a sample of 160 UBVCCD open star clusters of approximately128,000 stars near the galactic plane. The data was obtained and reducedfrom using the same reduction procedures, which makes this catalogue thelargest homogeneous source of open clusters' parameters.
| Morphological analysis of open clusters' propertiesI. Properties' estimations
A sample of 160 UBVCCD observations of open star clusters near thegalactic plane has been studied, and a catalogue of their propertiesobtained. The main photometrical properties have been re-estimated selfconsistently and the results have been compared with those of Lynga[Lynga, G., 1987. Catalog of Open Cluster Data, 5th Edition, StellarData Centers, Observatoire de Strasbourg, France].
| delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
| Variable stars in the open cluster Mel 71
The UBVI and time-series CCD photometric observations of theintermediate-age open cluster Mel 71 were carried out to search forvariable stars and obtain their physical parameters. By fitting the ZAMSto the observed color-color and color-magnitude diagrams, we estimated areddening value of the cluster E(B-V) = 0.20 +/- 0.05 and a distancemodulus (V-M_V)deg = 11.6 +/- 0.2. We also found its age ofabout log t = 9.0 from an isochrone fitting method for Z = 0.008. Usingthe observed time-series data, we carefully examined light variations of358 stars, fainter than 13.0m. Four delta Sct stars and one eclipsingbinary were discovered. They are located in the delta Sct instabilitystrip of the color-magnitude diagram. Incidence of variability withinthe instability strip is about 7%. Newly found delta Sct stars showcomplex light variations, implying that they have multiple pulsationfrequencies. The period of the binary star is estimated to be about0.678d.
| The STACC Open Cluster Target List
Observations of variable stars offer a potential to test stellarstructure and evolution. The observations can be either of single,isolated stars, or of variable stars in clusters. The STACC group(Frandsen 1992) has for the last several years searched for openclusters with a population of delta Scuti stars. To make this searchmore efficient, we have produced a target list with a number ofpromising open clusters. The list includes parameters, finding charts,Colour-Magnitude diagrams (CM diagrams) and references for the clusters.This target list is presented here, and is thus made available toobservers interested in participating in the search for variable starsin open clusters. In this paper we describe the motivation, contents anduse of the STACC Open Cluster Target List. We also give some guidelineson how to make CCD observations of open clusters in order to search forvariable stars.
| A search for delta Scuti stars in northern open clusters. I. CCD photometry of NGC 7245, NGC 7062, NGC 7226 and NGC 7654
In an effort to test stellar structure and evolution models, analysis ofoscillations in A and F stars in open clusters is carried out by theSTACC network (Frandsen \cite{stacc}). In this paper we describe oureffort to locate a suitable open cluster in the northern hemisphere fora future multi-site campaign. We present BV Johnson and time series CCDphotometry of four poorly studied open clusters: NGC 7245, NGC 7062, NGC7226 and NGC 7654. New improved colour-magnitude diagrams for these fournorthern hemisphere clusters, together with the results from the searchfor variable stars in the clusters are presented. The cluster reddening,distance and age are estimated from isochrone fitting. In the fourclusters, we discovered a total of two delta Scuti stars, one eclipsingbinary, one variable of unknown type and evidence for 3 potentialvariables all situated within the delta Scuti instability strip. We findthat the fraction of delta Scuti stars in these four open clusters ismuch lower than among field stars and in other open clusters suggestingthat some additional parameters control the pulsation, parameters thatwe do not understand at this moment.
| 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.
| A project for investigation of the stellar population of the galactic disk.
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| New Color Magnitude Diagrams for NGC 637 and NGC 7245
We present new color-magnitude diagrams for the open clusters NGC 637and NCG 7245. CCD images were taken in the UBVR system for NGC 637 andin the BVR system for NGC 7245 at the Lowell Observatory 42-inchtelescope. The distance modulus and the age are determined for bothclusters; the color excess for NGC 637 is derived. NGC 7245 has notpreviously been measured in the BVR system, and neither cluster has beenanalyzed photometrically with a CCD. The improved accuracy ofphotometric measurement of CCD images over photographic methods givesincreased accuracy for the age and distance.
| Component Analysis of Open Clusters
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| Young stellar-gas complexes in the Galaxy
It is found that about 90 percent of OB-associations and o-b2 clusterssituated within 3 kpc of the sun can be united into complexes withdiameters of 150-700 pc. Almost all of these clusters contain giantmolecular clouds with a mass greater than about 100,000 solar masses. Anumber of complexes are associated with giant H I clouds; a few of thesmall complexes are situated in the HI caverns. The concentration ofOB-associations and young clusters in star complexes attests to theircommon origin in the supergiant gaseous clouds.
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| Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters
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| 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.
| 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.
| Three colour photometry of the galactic star clusters NGC 7226, NGC 7245, IC 1442 and Be 94.
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