תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Red giants in open clusters. XII. Six old open clusters NGC 2112, 2204, 2243, 2420, 2506, 2682
Aims.We studied the membership and binarity of 123 red giants in six oldopen clusters, NGC 2112, 2204, 2243, 2420, 2506 and 2682, to define moreprecisely the evolutionary path on the red-giant branch. Methods: Theanalysis is based on 185 radial-velocity observations with the Coravelspectrographs and available photometric data. Results: The membershipof 93 red giants was confirmed on the basis of the radial velocities.Seven definitive spectroscopic binaries were identified and 11additional stars are suspected of being binaries. The binary frequency(19%) is slightly lower than average. This is partly due to the smallnumber of observations secured for each star. Orbital elements have beendetermined for the first time for the BaII star NGC 2420-173 (D) andthose of the other BaII star NGC 2420-250 (X) have been improved. Thevalues of the cluster mean velocities have been significantly improved. Conclusions: With the new membership estimates and binary detections,the existing CCD data allow precise definition of the red-giant loci. Anumber of stars in NGC 2506, 2420 and 2204 appear to define anasymptotic branch, the position of which differs significantly from thatpredicted by the models.Based on observations collected with the Danish 1.54-m and ESO 1-mtelescopes at the European Southern Observatory, La Silla, Chile.
| 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
| vbyCaHβ CCD Photometry of Clusters. VI. The Metal-deficient Open Cluster NGC 2420
CCD photometry on the intermediate-band vbyCaHβ system is presentedfor the metal-deficient open cluster NGC 2420. Restricting the data toprobable single members of the cluster using the CMD and the photometricindices alone generates a sample of 106 stars at the cluster turnoff.The average E(b-y)=0.035+/-0.003 (s.e.m.) or E(B-V)=0.050+/-0.004(s.e.m.), where the errors refer to internal errors alone. With thisreddening, [Fe/H] is derived from both m1 and hk, using b-yand Hβ as the temperature index. The agreement among the fourapproaches is reasonable, leading to a final weighted average of[Fe/H]=-0.37+/-0.05 (s.e.m.) for the cluster, on a scale where theHyades has [Fe/H]=+0.12. When combined with the abundances from DDOphotometry and from recalibrated low-resolution spectroscopy, the meanmetallicity becomes [Fe/H]=-0.32+/-0.03. It is also demonstrated thatthe average cluster abundances based on either DDO data orlow-resolution spectroscopy are consistently reliable to 0.05 dex orbetter, contrary to published attempts to establish an open clustermetallicity scale using simplistic offset corrections among differentsurveys.
| Blue Stragglers in Galactic Open Clusters and Integrated Spectral Energy Distributions
Synthetic integrated spectral properties of the old Galactic openclusters are studies in this work, in which 27 Galactic open clusters ofages >=1 Gyr are selected as the working sample. Based on thephotometric observations of these open clusters, a synthetic integratedspectrum has been made for the stellar population of each cluster. Theeffects of blue straggler (BS) stars on the conventional simple stellarpopulation (SSP) model are analyzed on an individual cluster basis. Itis shown that the BSs, whose positions in the color-magnitude diagramscannot be predicted by the current single-star evolution theory, requiresignificant modifications to the integrated properties of theoreticalSSP model. The synthesized integrated spectral energy distributions(ISEDs) of our sample clusters are dramatically different from those ofSSPs based on an isochrone only. The BS-corrected ISEDs of stellarpopulations show systematic enhancements toward shorter wavelengths inthe spectra. When measured with broadband colors in unresolvableconditions, the age of a stellar population can be seriouslyunderestimated by the conventional SSP model. Therefore, considering thecommon existence of BS components in real stellar populations, we shouldexpect considerable alterations of the conventional ISEDs when we applythe technique of evolutionary population synthesis to more complicatedstellar systems.
| Abundance Variations Within Globular Clusters
Abundance variations within globular clusters (GCs), and of GC starswith respect to field stars, are important diagnostics of a variety ofphysical phenomena, related to the evolution of individual stars, masstransfer in binary systems, and chemical evolution in high densityenvironments. The broad astrophysical implications of GCs as buildingblocks of our knowledge of the Universe make a full understanding oftheir history and evolution basic in a variety of astrophysical fields.We review the current status of the research in this field, comparingthe abundances in GCs with those obtained for field stars, discussing indepth the evidence for H-burning at high temperatures in GC stars,describing the process of self-enrichment in GCs with particularreference to the case of the most massive Galactic GC ( Cen), anddiscussing various classes of cluster stars with abundance anomalies.Whereas the overall pattern might appear very complex at first sight,exciting new scenarios are opening where the interplay between GCdynamical and chemical properties are closely linked with each other.
| On the recent star formation history of the Milky Way disk
We have derived the star formation history of the Milky Way disk overthe last 2 Gyr from the age distribution diagram of a large sample ofopen clusters comprising more than 580 objects. By interpreting the agedistribution diagram using numerical results from an extensive libraryof N-body calculations carried out during the last ten years, wereconstruct the recent star formation history of the Milky Way disk.Under the assumption that the disk has never been polluted by anyextragalactic stellar populations, our analysis suggests thatsuperimposed on a relatively small level of constant star formationactivity mainly in small-N star clusters, the star formation rate hasexperienced at least five episodes of enhanced star formation lastingabout 0.2 Gyr with production of larger clusters. This cyclic behaviourshows a period of 0.4+/-0.1 Gyr and could be the result of density wavesand/or interactions with satellite galaxies. On the other hand, the starformation rate history from a volume-limited sample of open clusters inthe solar neighbourhood appears to be consistent with the overall starformation history obtained from the entire sample. Pure continuous starformation both in the solar neighbourhood and the entire Galactic diskis strongly ruled out. Our results also indicate that, in the Milky Waydisk, about 90% of open clusters are born with N<=150 and the slopein the power-law frequency distribution of their masses is about -2.7when quiescent star formation takes place. If the above results arere-interpreted taking into consideration accretion events onto the MilkyWay, it is found that a fraction of the unusually high number of openclusters with ages older than 0.6 Gyr may have been formed in disruptedsatellites. Problems arising from the selection effects and the ageerrors in the open cluster sample used are discussed in detail.
| Abundances of Red Giants in the Old Open Cluster Collinder 261
We present an analysis of high-dispersion echelle spectra of four giantstars in the 8 Gyr open cluster Cr 261 obtained with the Cerro TololoInter-American Observatory's 4 m telescope. Abundances were determinedrelative to the bright, slightly metal-poor disk giant Arcturus. Cr 261is found to have a mean [Fe/H]=-0.22+/-0.05 (mean error). Oxygenabundances, determined from the forbidden [O I] lines, show roughlysolar or slightly depleted abundance ratios. The α-elements Mg,Ca, and Ti also show scaled solar abundance ratios, with suggestionsthat the Si abundance is slightly enhanced. The odd-Z elements Na and Alare significantly enhanced relative to scaled solar abundances. Theabundance results for Cr 261 are compared with those fromhigh-dispersion studies of other old open clusters in the literature,which, overall, show similar behavior in all these elements. None of theabundance ratios show significant trends with overall cluster [Fe/H] orwith cluster age.
| Analysing the database for stars in open clusters. I. General methods and description of the data
We present an overview and statistical analysis of the data included inWEBDA. This database includes valuable information such as coordinates,rectangular positions, proper motions, photometric as well asspectroscopic data, radial and rotational velocities for objects of openclusters in our Milky Way. It also contains miscellaneous types of datalike membership probabilities, orbital elements of spectroscopicbinaries and periods of variability for different kinds of variablestars. Our final goal is to derive astrophysical parameters (reddening,distance and age) of open clusters based on the major photometric systemwhich will be presented in a follow-up paper. For this purpose we havechosen the Johnson UBV, Cousins VRI and Strömgren uvbybetaphotometric systems for a statistical analysis of published data setsincluded in WEBDA. Our final list contains photographic, photoelectricand CCD data for 469 820 objects in 573 open clusters. We have checkedthe internal (data sets within one photometric system and the samedetector technique) and external (different detector technique) accuracyand conclude that more than 97% of all investigated data exhibit asufficient accuracy for our analysis. The way of weighting and averagingthe data is described. In addition, we have compiled a list of deviatingmeasurements which is available to the community through WEBDA.
| 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.
| Metallicities of Old Open Clusters
We present radial velocities and metallicities for a sample of 39 openclusters with ages greater than about 700 million years. For 24 clustersnew moderate-resolution spectroscopic data obtained with multiobjectspectrographs on the Kitt Peak National Observatory and the Cerro TololoInter-American Observatory 4 m telescopes are used to determine radialvelocities and mean cluster metallicities. These new results arecombined with data published previously by Friel & Janes to providea sample of 459 giants in 39 old open clusters, which are used toinvestigate radial abundance gradients in the Galactic disk. Based on anupdated abundance calibration of spectroscopic indices measuring Fe andFe-peak element blends, this larger sample yields an abundance gradientof -0.06+/-0.01 dex kpc-1 over a range in Galactocentricradius of 7 to 16 kpc. There is a slight suggestion of a steepening ofthe abundance gradient with increasing cluster age in this sample, butthe significance of the result is limited by the restricted distancerange for the youngest clusters. The clusters show no correlation ofmetallicity with age in the solar neighborhood. Consistent with theevidence for a steepening of the gradient with age, the clusters in theouter disk beyond 10 kpc show a suggestion at the 1.5 σ level of adependence of metallicity on age.
| The intermediate-age open cluster NGC 2112
We report on BVI charge-coupled device photometry of a field centred onthe region of the intermediate-age open cluster NGC 2112 down to V= 21.Owing to the smaller field coverage, we are able to limit the effect offield star contamination that, in the past, hampered precisedeterminations of the cluster age and distance. In this way, we provideupdated estimates of the fundamental parameters for NGC 2112. Havingextended the photometry to the I passband, we are able to construct acolour-colour diagram, from which we infer a reddening E(B-V) = 0.63 +/-0.14 mag. The comparison of the colour-magnitude diagram withtheoretical isochrones leads to a distance of 850 +/- 100 pc and an ageof 2.0 +/- 0.3 Gyr. While the distance is in agreement with previousdeterminations, the age turns out to be much better constrained andsignificantly lower than previous estimates.
| 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.
| Abundance Gradient from Open Clusters and Implications for the Galactic Disk Evolution
We compile a new sample of 89 open clusters with ages, distances andmetallicities available. We derive a radial iron gradient of about-0.099±0.008 dexkpc (unweighted) for the whole sample, which issomewhat greater than the most recent determination of oxygen gradientfrom nebulae and young stars. By dividing the clusters into age groups,we show that the iron gradient was steeper in the past and has evolvedslowly in time. Current data show a substantial scatter of the clustermetallicities indicating that the Galactic disk has undergone a veryrapid, inhomogeneous enrichment.Also, based on a simple, but quitesuccessful model of chemical evolution of the Milky Way disk, we make adetailed calculation of the iron abundance gradient and its timeevolution. The predicted current iron gradient is about -0.072 dexkpc.The model also predicts a steady flattening of the iron gradient withtime, which agrees with the result from our open cluster sample.
| Statistics and supermetallicity: The metallicity of NGC 6791
For the old galactic cluster NGC 6791, Peterson & Green(\cite{pg98a}) and Chaboyer et al. (\cite{cgl99}) have found that [Fe/H]~ +0.4 dex. A second look at that conclusion is taken in this paper.Zero-point problems are reviewed for a high-dispersion analysis done byPeterson & Green, and it is found that accidental errors have notbeen determined rigorously for the results of that analysis. It is alsonoted that in a color-magnitude analysis performed by Chaboyer et al.,the important metallicity range between 0.0 and +0.3 dex is not exploredand hence is not ruled out. Moreover, that analysis does not yieldstatistically rigorous results, and it appears that such results may notbe produced in color-magnitude analysis of clusters in general. Resultsin the two cited papers and elsewhere are re-evaluated statistically,with an allowance being made for uncertainty in the cluster reddening.Apparently the best that can be said at present is that the clustermetallicity lies in the range from +0.16 to +0.44 dex. This conclusionis stressed by reviewing the immaturity of the underlying data base. Thepremature conclusion for a high metallicity turns out to be due largelyto neglect of accidental errors, though a tendency to ascribe too muchweight to high derived metallicities may also play a role.
| Proper motions of open clusters within 1 kpc based on the TYCHO2 Catalogue
We present mean absolute proper motions of 112 open clusters, determinedusing the data from the Tycho2 Catalogue. For 28 clusters, this is thefirst determination of proper motion. The measurements made use of alarge number of stars (usually several tens) for each cluster. The totalnumber of stars studied in the fields of the 164 open clusters is 5016,of which 4006 were considered members. The mean proper motions of theclusters and membership probability of individual stars were obtainedfrom the proper motion data by applying the statistical method proposedby Sanders (\cite{Sanders71}). Based on observations of the ESAHipparcos satellite. Tables 1, 2 and 5 to 117 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/376/441
| 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].
| Foreground and background dust in star cluster directions
This paper compares reddening values E(B-V) derived from the stellarcontent of 103 old open clusters and 147 globular clusters of the MilkyWay with those derived from DIRBE/IRAS 100 mu m dust emission in thesame directions. Star clusters at |b|> 20deg showcomparable reddening values between the two methods, in agreement withthe fact that most of them are located beyond the disk dust layer. Forvery low galactic latitude lines of sight, differences occur in thesense that DIRBE/IRAS reddening values can be substantially larger,suggesting effects due to the depth distribution of the dust. Thedifferences appear to arise from dust in the background of the clustersconsistent with a dust layer where important extinction occurs up todistances from the Plane of ~ 300 pc. For 3 % of the sample asignificant background dust contribution might be explained by higherdust clouds. We find evidence that the Milky Way dust lane and higherdust clouds are similar to those of several edge-on spiral galaxiesrecently studied in detail by means of CCD imaging.
| Some Revised Observational Constraints on the Formation and Evolution of the Galactic Disk
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.2556T&db_key=AST
| Chemical abundances in the Outer Disk Clusters Tombaugh 2, Melotte 71, and NGC 2112
Abstract image available at:http://adsabs.harvard.edu/abs/1996AJ....112.1551B
| 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.
| Integrated photometric properties of open clusters
Galactic open clusters provide an abundant sample of stellar aggregatesof various sizes, ages and metal abundances, apt to constitute atemplate for comparison with star systems in other galaxies. In thispaper we present and discuss a standard methodology to synthesize U,B,Vfluxes and colours, and apply it to a set of 138 open clusters. Resultsare compared with previous ones available in the literature. We wereable to calibrate a mass-luminosity relation by which we evaluated themass of ~400 open clusters, leading to a well defined present-day massfunction. The number-complete sample of galactic open clusters presentedin Battinelli & Capuzzo-Dolcetta (1991) is enlarged of a 15%.
| Development of the Galactic disk: A search for the oldest open clusters
In an extensive charge coupled devices (CCD) photometric survey ofpotential old open clusters, we have identified a number of systems thatare indeed old; some of them are among the oldest of the open clusters.Using our versions of two well-known morphological age indices, onebased on the luminosity difference between the main sequence turnoff andthe horizontal branch and the other on the color difference between theturnoff and the giant branch, we have ranked the open clusters inapproximate order of age. Our data together with previously publishedphotometry of other old open clusters, yields a catalogue of 72 clustersof the age of Hyades or older with 19 of the clusters as old or olderthan M67 (about 5 Gyr). Among the oldest open clusters are Be 17, Cr261, NGC 6791, Be 54, and AM 2. Be 17 and another old cluster, Lynga 7,are possibly as old as the youngest globulars. The data also suggestthat the formation rate of open clusters may have been higher early inthe history of the disk than at intermediate times since numerousclusters have survived from that time.
| Metallicities and radial velocities of old open clusters
Medium resolution spectra of giant stars in 24 open clusters with agesgreater than about 1 Gyr have been obtained and analyzed to provideradial velocities accurate to 10-15 km/s and (Fe/H) metallicitiesaccurate to 0.15 dex. The radial velocities of the older cluster systemsare consistent with those expected from the reflex of solar motion andsimple Galactic rotation. The cluster kinematics suggest strongly thatthey are drawn from the old thin disk stellar population. An abundancegradient in the Galactic disk of -0.09 +/- 0.02 dex/kpc is found. Thisgradient is in good agreement with that found for samples of youngeropen clusters, suggesting that there has been little change in theGalactic radial abundance gradient over time. The cluster sample showsno correlation between age and metallicity, regardless of Galactocentricradius. The clusters show an unexpected correlation between the Mg linestrength and age of the cluster at a fixed metallicity. Possible reasonsfor this are discussed.
| CCD BVR photometry of the open cluster IC 1311
Six CCD frames for two fields in the area of the rich, presumably old,and unstudied open cluster IC 1311 have been obtained in the BVR bands.The photometric analysis leads to an estimated age of between 1 Gyr(standard models) and 2 Gyr (overshooting models), placing the clusterat a distance of about 4.8 kpc from the sun. Comparison of theobservational color-magnitude diagram (CMD) with model isochronesproduces a good fit for a metallicity of Z = 0.006-0.008. Somemorphological features displayed by the CMD of this cluster are betterunderstood in terms of convective overshooting rather than by classicaltheories. The location of IC 1311 on the age-metallicity diagramsuggests an ecological environment for its formation more similar tothat found in the LMC than in the solar vicinity.
| An improved metal abundance calibration for the Washington system
The determination of metal abundances for individual giants fromWashington photometry is revised, with several significant improvementsincorporated. The solar-abundance two-color relations are revamped withthe inclusion of new observations of a large sample of solar-abundancegiants with small reddenings, especially those with late-K spectraltypes. The new relations are very similar to the original ones derivedin C76 except for a zero-point offset. A new temperature index, M-T2, isinvestigated, as well as a new abundance index, C-T1, in addition to thestandard indices. The M-T2 index has a much broader baseline and thus amuch larger range than T1-T2, and is therefore less susceptible tophotometric errors. The significant decrease in abundance sensitivityfor cooler stars, suspected by previous investigations, is confirmed byincluding observations of a number of giants with a range in temperaturein each of a large sample of open and globular clusters. A procedure forcorrecting the abundance indices for cool stars is derived whichsignificantly improves the metallicity determination.
| An observational age-metallicity relation for the Galaxy
An observational Age-Metallicity Diagram for the Galaxy has beenconstructed on the base of star cluster data available in theliterature. This diagram exhibits two independent and simultaneousmetallicity enhancement processes identified with two dynamical galacticsubstructures: the thin and the thick disks. Within the observationaluncertainties both these processes can be satisfactory approximated byInfall-Inflow models of the chemical evolution with different high,although rapidly decaying with time, Star Formation and Infall Rates.The comparison of the galactic age-metallicity relations with that forthe Large Magellanic Cloud shows some similarities between processes ofthe chemical enhancement in the Large Magellanic Cloud and the Thin Disksubsystem in the Galaxy.
| The origin and abundances of the chemical elements revisited
A review of significant advances and refinements to the basic theory ofnucleosynthesis is presented to show that the original theory iseffective. Astronomical observations and theories are described in termsof their support to the theory. Important findings mentioned include theresolution of heavy-element burning into the burning of separateelements, the observation of elemental and isotopic ratios beyond thesolar system, and theories which show that elements up to helium couldhave been produced in the early universe. Observed abundances arediscussed in detail, and the processes and sites are also discussed withrespect to the original ideas of nucleosynthesis theory. Observedastronomical abundances and calculations of large nuclear reactionnetworks are found to support nucleosynthesis, and the basic processstructure has not changed.
| Metallicities of open clusters
An examination is conducted of available metallicity data on openclusters, gathering the largest possible set of homogeneous estimationsof this parameter and determining whether open cluster metallicities arerelated to the spatial and age distributions of such objects. The'composite' C-M diagrams for the two metallicity groups discussedexhibit interesting morphological differences which may be characterizedas the presence of numbered blue stragglers at the two metal-richclusters and a lack of such members in two metal-poor ones.
| Photometry and spectroscopy of the open cluster NGC 2112
Photometric and spectroscopic data are presented for the open clusterNGC 2112. An age between 3 and 5 Gyr is obtained, depending onmetallicity. Stromgren data indicate a low value of about -1 dex, whileG-band strengths of probable members seem to be weaker than those ofstars in M 67, NGC 2243, Mel 66, which serve as comparison objects. Sucha combination of age and metallicity is unique among star clusters.Spectral classification of several stars leads to a reddening value of E(B-V) = 0.6. The distance of NGC 2112 is of the order of 700-800 pc.
| Two populations of open clusters
The paper proposes a division of the local open clusters into twodifferent dislike subpopulations on the base of the metallicityenhancement history, spatial distribution in the Galaxy and morphologyof their C-M diagrams. The thin disk population objects exhibit highermetallicities and are more closely concentrated to the center and thedisk of the Galaxy than the thick disk clusters. The former contain alsofrequently blue stragglers while the later exhibit the presence of Clumpgiant members, typical for the thick disk globular clusters. Kinematicalproperties of the two considered open cluster subpopulations remainunknown due to the lack of observational data.
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
קטלוגים וכינוים:
|
