scholarly journals Chemical Properties of Individual Globular Clusters

1980 ◽  
Vol 85 ◽  
pp. 385-400 ◽  
Author(s):  
Judith G. Cohen
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Chemical Properties ◽  
High Dispersion ◽  
The Past ◽  
The Many

Rapid improvements in instrumentation over the past few years have made the spectroscopic study of individual globular cluster giants feasable. Three years ago I began a program of high dispersion abundance analyses of such stars to provide a calibration for the many photometric systems used to rank globular clusters in metallicity. The results for four clusters (M92, M15, M13, and M3) of low and intermediate metallicity have already appeared (Cohen, 1978, 1979), and additional detailed analyses of stars in M5 and M13 (Pilachowski, Wallerstein and Leep, 1979) will soon be available. Ignoring the elements C, N, and O, to which we shall return later, these detailed abundance analyses yielded few great surprises; perhaps the metallicity scale that had previously been used was too high by about 0.2 dex, and also it became clear that M3 was a very metal poor cluster. However, the calibration of the metal rich globulars beyond the simple ranking level of Mould, Struthman, and McElroy (1979) had not been attempted.

Recent Advances in High Dispersion Spectroscopy of Globular Cluster Stars

1988 ◽  
Vol 132 ◽  
pp. 525-530
Author(s):  
Raffaele G. Gratton
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
High Dispersion ◽  
Photographic Material ◽  
Recent Advances ◽  
Metal Abundances ◽  
Ccd Detectors ◽  
Major Progress

The use CCD detectors has allowed a major progress in abundance derivations for globular cluster stars in the last years. Abundances deduced from high dispersion spectra now correlates well with other abundance indicators. I discuss some problems concerning the derivation of accurate metal abundances for globular clusters using high dispersion spectra from both the old photographic and the most recent CCD data. The discrepant low abundances found by Cohen (1980), from photographic material for M71 giants, are found to be due to the use of too high microturbulences.

scholarly journals The Composition of Warm Giants in M 71 and M 5

1988 ◽  
Vol 126 ◽  
pp. 497-498
Author(s):  
Catherine A. Pilachowski ◽  
Christopher Sneden
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
High Dispersion ◽  
High Signal ◽  
Signal To Noise

In 1979 a disturbing controversy arose in the field of globular cluster research when Cohen (1980) and Pilachowski, Canterna, and Wallerstein (1980) announced the results of the first high dispersion studies of the composition of giants in the globular clusters M 71 and 47 Tucanae. In contrast to earlier studies, which found metallicities of typically −0.3 and −0.5 dex, these investigators obtained values of −1.3 and −1.1. Since then, many have attempted to redetermine the abundances of M 71 and 47 Tuc to explain the discrepant results. These efforts have all suffered from the absence of high signal-to-noise, high resolution spectra of stars with temperatures above 4300 K.

scholarly journals Spectroscopic Study of Cepheids in the Globular Cluster Omega Cen

1993 ◽  
Vol 139 ◽  
pp. 378-379
Author(s):  
Guillermo Gonzalez ◽  
George Wallerstein
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Preliminary Report ◽  
Globular Clusters ◽  
Spectroscopic Studies ◽  
Horizontal Branch ◽  
Present Sample ◽  
Abundance Patterns

AbstractUntil now there have been few spectroscopic studies of cepheids in globular clusters. In this preliminary report we present sample spectra of the stars Vl and V29 in ω Cen. Eventually, we hope to use the abundance patterns, masses, and period changes of cepheids to better understand post-horizontal branch evolution in globular clusters.

scholarly journals Commission 37: Star Clusters and Associations

1982 ◽  
Vol 18 (1) ◽  
pp. 499-526
Keyword(s):  
Globular Cluster ◽  
Working Group ◽  
Globular Clusters ◽  
Star Clusters ◽  
Open Clusters ◽  
General Assembly ◽  
Active Period ◽  
Star Clusters And Associations ◽  
The Past ◽  
Good Number

The past triennium has been a very active period in most branches of cluster research. Some controversial subjects, notably globular cluster abundances and ages have received much attention. A good number of photometric papers on clusters as well as associations have been published. Observational effects of mass loss have been discussed by several astronomers.This report has been assembled by the president of the commission although several sections have been contributed by other members. The report will first list some highlights in the activities of our commission. Then follow the tables containing current investigations of OB associations, open clusters and globular clusters. These have been assembled by B. Balázs, G. Harris and R. White, respectively. After these tables comes a section by D. Heggie about dynamics of star clusters. A working group under the chairmanship of A. Moffat has made a proposal about the numbering of stars in clusters. The proposal, which is included here will be discussed by our commission at the IAU General Assembly.

scholarly journals The Spectra of Wolf-Rayet Stars at High Dispersion

1973 ◽  
Vol 49 ◽  
pp. 57-92
Author(s):  
M. K. V. Bappu
Keyword(s):  
Southern Hemisphere ◽  
Spectral Resolution ◽  
Emission Band ◽  
Emission Lines ◽  
High Dispersion ◽  
Wide Limit ◽  
The Past ◽  
Individual Features ◽  
Large Width ◽  
The Many

The Wolf-Rayet stars have perhaps the most spectacular spectra among the various celestial species that have been examined with the aid of the spectrograph. The wide emission lines that provide a striking display continue to be the enigma they have been for decades. Progress, however, in evaluating the contributions to the spectrum by different ions has been fairly complete, thanks to the splendid efforts in the laboratory by Edlen and his collaborators. Many lists of wavelengths of individual features exist from the studies of Plaskett, Beals, Cecilia Payne and Swings. Efforts at identification have been such as to provide a list of likely contributors, that by wavelength position and plausible intensity could be present in the emission band at a specified wavelength. The large width of the lines form the principal limitation. For, one can have a wide limit of coincidence in wavelength with resultant emission features that are complexes covering well over a hundred Ångstrőms. The wide nature of these complexes have perhaps encouraged in the past the use of low spectral resolution only, for the many studies that have been carried out. Seldom has one used the resolutions and dispersions that have been usefully employed for the study of the more common relatively narrow absorption lined objects. This situation pertaining to the Wolf-Rayet stars is happily undergoing a change in recent years when coudé spectra with the larger telescopes are becoming increasingly available. The southern hemisphere has been particularly rich in these objects both in variety of behaviour and in having many bright ones, and one can, therefore, justifiably hope that our information on these objects will progress henceforth with remarkable rapidity.

scholarly journals Do Halo Field Stars and Globular Clusters Belong to the Same Population?

1983 ◽  
Vol 6 ◽  
pp. 129-137 ◽  
Author(s):  
Robert P. Kraft
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Helium Content ◽  
The Past ◽  
Solar Motion ◽  
Trigonometric Parallaxes ◽  
The Common ◽  
Existent Problem

Obviously such transcendental issues as the helium content and age of the oldest stars depend on whether we are correct in our belief that the answer to this question is “yes” I hardly need say that over the past 40 years compelling affirmative arguments have been developed. Thus, for example, the solar motion of the common subdwarfs can be shown (e.g., Carney 1979) to be essentially identical with that of globular clusters (Kinman 1959) (Table 1), and the Fe-peak metallicities of giants and RR Lyraes in the halo field have been shown to be the same as those in clusters [see, e.g., recent reviews by Kraft (1979) and Freeman and Norris (1981)]. It is hard to believe that we would be incorrect in identifying the main sequence of a globular cluster with the main sequence defined by the trigonometric parallaxes, magnitudes and colors of subdwarfs having the same [Fe/H]. It might seem, therefore, that raising such an issue at this late date is equivalent to discussing a non-existent problem.

scholarly journals The Globular Clusters of M31: Keys to its Formation History

2002 ◽  
Vol 207 ◽  
pp. 52-57
Author(s):  
Kathy Perrett ◽  
Terry Bridges ◽  
Dave Hanes ◽  
Mike Irwin ◽  
Dave Carter ◽  
...  
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Cluster System ◽  
Radial Velocities ◽  
Galaxy Halos ◽  
Formation History ◽  
Globular Cluster System ◽  
William Herschel ◽  
Existing Data

With the ultimate goal of distinguishing between various models describing the formation of galaxy halos (e.g., radial collapse, chaotic mergers), we present the results of a spectroscopic study of the globular cluster system of M31. We have obtained deep, intermediate-resolution spectra for several hundred of the M31 globular clusters using the WYFFOS fibre-fed spectrograph at the William Herschel Telescope. These observations have yielded precise radial velocities and metallicities for over 200 members of the M31 globular cluster population, the vast majority of which represent new data or significant improvements over pre-existing data.

scholarly journals Absolute Proper and Space Motion of the Globular Cluster M2

1994 ◽  
Vol 161 ◽  
pp. 464-466
Author(s):  
M. Geffert ◽  
C. Forner ◽  
M. Hiesgen ◽  
A.R. Klemola
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Reference Frames ◽  
Proper Motions ◽  
The Past ◽  
Motion Study ◽  
Space Motion ◽  
First Results

Space motions of globular clusters are important for the understanding of the kinematics and chemical evolution of the Milky Way. The greatest problem for the determination of the space motions of the globular clusters arises from the difficulties of getting absolute proper motions. In the past these were determined using classical stellar reference frames, modelling of the non-cluster stars in the field and extragalactic objects in the region of the cluster (see e.g. Cudworth & Hanson 1993; Geffert et al. 1993 for references). However, as shown for M 15 and M 3 (Geffert et al. 1993; Tucholke et al. 1993), the results based on different methods for deriving the absolute proper motions differ by up to yrs. In order to get a more complete view of the differences between the various methods it is therefore very interesting to get absolute proper motions based on all three methods for further objects. We present here the first results of a new proper motion study of the globular cluster M 2.

scholarly journals The enigmatic globular cluster UKS 1 obscured by the bulge: H-band discovery of nitrogen-enhanced stars

2020 ◽  
Vol 643 ◽  
pp. A145 ◽  
Author(s):  
José G. Fernández-Trincado ◽  
Dante Minniti ◽  
Timothy C. Beers ◽  
Sandro Villanova ◽  
Doug Geisler ◽  
...  
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Strong Evidence ◽  
Proper Motion ◽  
Spectroscopic Data ◽  
Globular Clusters ◽  
Elemental Abundances ◽  
The Mean ◽  
Lower Carbon ◽  
Good Agreement

The presence of nitrogen-enriched stars in globular clusters provides key evidence for multiple stellar populations (MPs), as has been demonstrated with globular cluster spectroscopic data towards the bulge, disk, and halo. In this work, we employ the VVV Infrared Astrometric Catalogue (VIRAC) and the DR16 SDSS-IV release of the APOGEE survey to provide the first detailed spectroscopic study of the bulge globular cluster UKS 1. Based on these data, a sample of six selected cluster members was studied. We find the mean metallicity of UKS 1 to be [Fe/H] = −0.98 ± 0.11, considerably more metal-poor than previously reported, and a negligible metallicity scatter, typical of that observed by APOGEE in other Galactic globular clusters. In addition, we find a mean radial velocity of 66.1 ± 12.9 km s−1, which is in good agreement with literature values, within 1σ. By selecting stars in the VIRAC catalogue towards UKS 1, we also measure a mean proper motion of (μαcos(δ), μδ) = (−2.77 ± 0.23, −2.43 ± 0.16) mas yr−1. We find strong evidence for the presence of MPs in UKS 1, since four out of the six giants analysed in this work have strong enrichment in nitrogen ([N/Fe] ≳ +0.95) accompanied by lower carbon abundances ([C/Fe] ≲ −0.2). Overall, the light- (C, N), α- (O, Mg, Si, Ca, Ti), Fe-peak (Fe, Ni), Odd-Z (Al, K), and the s-process (Ce, Nd, Yb) elemental abundances of our member candidates are consistent with those observed in globular clusters at similar metallicity. Furthermore, the overall star-to-star abundance scatter of elements exhibiting the multiple-population phenomenon in UKS 1 is typical of that found in other global clusters (GCs), and larger than the typical errors of some [X/Fe] abundances. Results from statistical isochrone fits in the VVV colour-magnitude diagrams indicate an age of 13.10−1.29+0.93 Gyr, suggesting that UKS 1 is a fossil relic in the Galactic bulge.

scholarly journals Studies Through Radial Velocity Measurements of the Peculiar Motions of Stars in Galactic Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 61-70
Author(s):  
G. Meylan
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Relative Importance ◽  
Parametric Methods ◽  
Single Object ◽  
Velocity Measurements ◽  
Light Spectra ◽  
The Past ◽  
Scientific Outputs

In a brief introduction, we first compare, in the framework of globular cluster dynamics, the relative importance of the amounts of information acquired, during the past decades, through proper motion and radial velocity measurements. Next, we review the most recent and important studies based on measurements of radial velocities obtained with single-object and multi-object spectrometers and interpreted with the use of King-Michie and Fokker-Planck models or with non-parametric methods. Then, we present the results obtained from integrated-light spectra in the cores of a few collapsed globular clusters. We conclude with a summary of the most important scientific outputs secured from the radial velocity measurements of stars in globular clusters.

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