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|CCD photometric search for peculiar stars in open clusters. VIII. King 21, NGC 3293, NGC 5999, NGC 6802, NGC 6830, Ruprecht 44, Ruprecht 115, and Ruprecht 120|
Context: We continue our survey of magnetic chemically peculiar (CP2)stars in galactic open clusters to shed more light on their origin andevolution. Aims: To study the group of CP2 stars, it is essential tofind these objects in different galactic environments and at a widerange of evolutionary stages. The knowledge of open cluster ages andmetallicities can help for finding a correlation between theseparameters and the (non-)presence of peculiarities, which has to betaken into account in stellar evolution models. Methods: Theintermediate band Δ a photometric system samples the depth of the5200 Å flux depression by comparing the flux at the centre withthe adjacent regions with bandwidths of 110 Å to 230 Å. Itis capable of detecting magnetic CP2 and CP4 stars with high efficiency,but also the groups of (metal-weak) λ Bootis and classicalBe/shell stars can be successfully investigated. In addition, it allowsthe age, reddening, and distance modulus to be determined withappropriate accuracy by fitting isochrones. Results: From the 1677observed members of the eight open clusters, one Ae and twenty-five CP2stars were identified. Furthermore nineteen deviating stars aredesignated as questionable for several reasons. The estimated age,reddening, and distance for the programme clusters were compared withpublished values of the literature and discussed in this context. Conclusions: .The current paper shows that CP2 stars are continuouslypresent in very young (7 Myr) to intermediate age (500 Myr) openclusters at distances greater than 2 kpc from the Sun.Based on observations at CASLEO, CTIO (Proposal 2003A-0057), and OSN.The Observatorio de Sierra Nevada is operated by the Consejo Superior deInvestigaciones Científicas through the Instituto deAstrofísica de Andalucía (Granada, Spain). Photometricdata are only avaialable in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/462/591 Full Fig. [seefull textsee full textsee full textsee full textsee full text], Tables[see full textsee full textsee full textsee full textsee full text] and[see full textsee full textsee full textsee full textsee full text] areonly available in electronic form at http://www.aanda.org
|On the current status of open-cluster parameters|
We aim to characterize the current status of knowledge on the accuracyof open-cluster parameters such as the age, reddening and distance.These astrophysical quantities are often used to study the globalcharacteristics of the Milky Way down to the very local stellarphenomena. In general, the errors of these quantities are neglected orset to some kind of heuristic standard value. We attempt to give somerealistic estimates for the accuracy of available cluster parameters byusing the independently derived values published in the literature. Intotal, 6437 individual estimates for 395 open clusters were used in ourstatistical analysis. We discuss the error sources depending ontheoretical as well as observational methods and compare our resultswith those parameters listed in the widely used catalogue by Dias et al.In addition, we establish a list of 72 open clusters with the mostaccurate known parameters which should serve as a standard table in thefuture for testing isochrones and stellar models.
|CCD photometric search for peculiar stars in open clusters. VI. NGC 1502, NGC 3105, Stock 16, NGC 6268, NGC 7235 and NGC 7510|
In a sample of six young open clusters (NGC 1502, NGC 3105, Stock 16,NGC 6268, NGC 7235, and NGC 7510) we investigated 1753 objects using thenarrow band, three filter Δ a photometric system resulting in thedetection of eleven bona-fide magnetic chemically peculiar (CP) starsand five Be or metal-weak stars. The results for the distant cluster NGC3105 is most important because of the still unknown influence of theglobal metallicity gradient of the Milky Way. These findings confirmthat CP stars are present in open clusters of very young ages (log t≥ 6.90) at galactocentric distances up to 11.4 kpc. For all programmeclusters the age, reddening, and distance modulus were derived using thecorresponding isochrones. Some additional variable stars within Stock 16could be identified by comparing different photometric studies.
|A multicolour CCD photometric and mass function study of the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253|
We derive cluster parameters and mass functions from new UBVRI CCDphotometric observations of ~3500 stars reaching down to V~20mag for thedistant southern open star clusters NGC 3105, NGC 3603, Melotte 105,Hogg 15, NGC 4815, Pismis 20 and NGC 6253. For NGC 3105 and Hogg 15, CCDdata are presented for the first time. The reddening is non-uniformacross the face of the young (age <300Myr) clusters NGC 3105, NGC3603, Melotte 105, Hogg 15 and Pismis 20, with average values ofE(B-V)=1.06, 1.44, 0.52, 1.15 and 1.20mag respectively, while it isuniform with average values of E(B-V)=0.72 and 0.20mag for the olderclusters NGC 4815 and 6253 respectively. The values of colour excessratios indicate the presence of normal interstellar reddening across thecluster regions studied here. Well-defined main sequences can be seen inall the clusters. However, main-sequence turn-off points and subgiantbranches are well defined only in the older clusters NGC 4815 and 6253.The distances to the clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15,NGC 4815, Pismis 20 and NGC 6253 are 9.5+/-1.5, 7.2+/-1.2, 2.3+/-0.2,3.0+/-0.3, 2.75+/-0.2, 3.55+/-0.35 and 1.8+/-0.12kpc respectively, whilethe corresponding ages derived using theoretical convective coreovershooting stellar evolutionary isochrones are 25+/-10, 3+/-2,250+/-30, 6+/-2, 400+/-50, 6+/-2 and 2500+/-600Myr respectively. In themass range ~1-75Msolar, the mass functions of all clustersexcept for NGC 6253 have been studied. The slopes of their mass spectraagree within errors with the Salpeter value (1.35). The slope of themass function for stars more massive than 10Msolar is almostthe same as for the lower mass stars. The mass function slopes ofclusters younger than 500Myr seem to have no dependence on Galacticlongitude, Galactocentric distance and cluster age. As the inherentuncertainties in the mass function determinations of young Galactic starclusters can produce internal scatter that is larger than the externalscatter, we conclude that, above 1Msolar, the initial massfunction is universal with a slope of Salpeter value.
|Absolute proper motions of 181 young open clusters.|
|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.
|Catalogue of UBV Photometry and MK Spectral Types in Open Clusters (Third Edition)|
|Integrated Photometric Parameters of Open and Globular Clusters|
|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.
|NGC 3105 - Further photoelectric UBV observations|
NGC 3105 (galactic longitude 279.92 deg, latitude +0.28 deg) isconfirmed to be a distant young cluster located 5.5 kpc from the sun onthe basis of photoelectric photometry of 34 stars. Its mean B-V colorexcess is 1.08 plus or minus 0.03 (m.e.). The earliest spectral type isB2, making NGC 3105 a useful spiral tracer. It contains six probablesupergiants: three red, one yellow, and two blue, one of the latterbeing confirmed spectroscopically. One of the red supergiants appears tobe one component of a red-blue close binary. Three Be stars are alsoprobable members.
|Uniform survey of clusters in the southern Milky Way.|
Abstract image available at:http://adsabs.harvard.edu/abs/1975AJ.....80...11V
|NGC 3105, a young very distant cluster in VELA|
Abstract image available at:http://adsabs.harvard.edu/abs/1974A&AS...16...25M
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