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Chemical analysis of the bulge globular cluster NGC 6553
No full textThis work presents the analysis of a sample of 558 red giant stars located in
the direction of the Bulge globular cluster NGC 6553 and observed with the
multi-object spectrograph FLAMES at the Very Large Telescope of ESO.
According to their metallicity and radial velocity, we identified a sample of
245 stars likely members of the cluster. This represents the largest spectroscopic sample collected so far for NGC 6553.
The main goal was to obtain detailed abundances of NGC 6553 with the purpose of studying its chemical composition and investigate its relation with
the formation of the Bulge and with other Bulge clusters. In particular, the
study aimed at verifying the possible presence of iron spread, which would
have revealed a complex nature of NGC 6553, in spite of its standard classification as a genuine globular cluster. Moreover, we investigated, the presence
of chemical anomalies through the measure of the Mg and Al abundances
that show large star-to-star variations in most of the Galactic clusters.
The analysis has revealed that NGC 6553 has an iron abundance of [Fe/H]
= −0.13 ± 0.01 dex with no significant internal spread. This result indicates
that the cluster was not able to retain the supernovae ejecta in its potential
well.
The [Si/Fe] abundance ratio is enhanced with respect to the solar value, indicating that the cluster was formed from gas enriched by supernovae ejecta.
The [Si/Fe] measured in NGC 6553 is compatible with that measured in other Bulge stars.
Finally, NGC 6553 does not exhibit a Mg-Al anti-correlation and no significant spread in either Mg and Al. This suggests that the massive stars populating the cluster in its early stage did not reach in their interior burning
temperatures higher than ∼ 70 million K
VLT-UVES abundance analysis of four giants in NGC 6553
Get PDFContext. Metal-rich globular clusters trace the formation of bulges. Abundance ratios in the metal-rich globular clusters such as NGC 6553 can constrain the formation timescale of the Galactic bulge.
Aims. The purpose of this study is to determine the metallicity and elemental ratios in individual stars of the metal-rich bulge globular cluster NGC 6553.
Methods. A detailed abundance analysis of four giants in NGC 6553 is carried out, based on optical high-resolution echelle spectra obtained with UVES at the ESO VLT-UT2 Kueyen telescope.
Results. A metallicity [Fe/H] = -0.20 dex is derived, together with alpha-element enhancement of Mg and Si ([Mg/Fe] = +0.28, [Si/Fe] = +0.21), solar Ca and Ti ([Ca/Fe]=+0.05, [Ti/Fe] = -0.01), and a mild enhancement of the r-process element Eu with [Eu/Fe]=+0.10. A mean heliocentric radial velocity of -1.86 km s(-1) is measured. We compare our results with previous investigations of the cluster
GC-MS chromatogram of secondary metabolites from <i>P</i>. <i>lilacinum</i> 6553 isolate (PNG).
No full textGC-MS chromatogram of secondary metabolites from P. lilacinum 6553 isolate (PNG).</p
The metal-rich globular cluster NGC 6553 : observations with WFPC2, STIS, and NICMOS
Get PDFWe present a Hubble Space Telescope study of the metal-rich globular cluster NGC 6553 using WFPC2, NICMOS, and STIS. Our primary motivation is to calibrate the STIS broadband LP magnitude against V555 and I814 magnitudes for stars of known metallicity and absolute (visual) magnitude, for application to our study of LMC globular clusters. NGC 6553 has been shown in earlier studies to have a very unusual color-magnitude diagram, so we also use our data to investigate the reddening, distance, luminosity function, and structure of this cluster. We deduce a higher metallicity and smaller distance modulus than did some previous studies, but we emphasize that very large patchy extinction on small angular scales prohibits accurate determination of the parameters of this cluster. The horizontal branch of NGC 6553 in (V,V−I) is tilted at an angle close to that of the reddening vector. We show that extinction does not, however, explain the tilt, which is presumably a metallicity eect. The colormagnitude diagram shows an apparent second turno some 1.5 mag fainter than that of the cluster. We show that this is most likely the background Galactic bulge: however, in that case, the color-magnitude diagram of NGC 6553 is not a good match to that of the field bulge population. The cluster is probably more metal-rich than is the mean Ðeld bulge star
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
An Abundance Analysis for Five Red Horizontal-Branch Stars in the Extremely Metal-rich Globular Cluster NGC 6553
Get PDFWe provide a high-dispersion line-by-line abundance analysis of five red horizontal-branch (HB) stars in the extremely metal-rich Galactic globular cluster NGC 6553. These red HB stars are significantly hotter than the very cool stars near the tip of the giant branch in such a metal-rich globular cluster, and hence their spectra are much more amenable to an abundance analysis than would be the case for red giants. We find that the mean [Fe/H] for NGC 6553 is -0.16 dex, comparable to the mean abundance in the Galactic bulge found by McWilliam & Rich and considerably higher than that obtained from an analysis of two red giants in this cluster by Barbuy and coworkers. The relative abundance for the best-determined α-process element (Ca) indicates an excess of α-process elements of about a factor of 2. The metallicity of NGC 6553 reaches the average of the Galactic bulge and of the solar neighborhood
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Metallicity of the star III-17 in the bulge globular cluster NGC 6553
Get PDFCCD échelle spectra were obtained at the 3.6 m telescope at ESO for the star III-17 of the metal-rich globular cluster NGC 6553. This cluster was chosen because it is a relatively dose bulge globular cluster and also it presented the possibility to be among the most metal-rich ones in the Galaxy. The metallicity of the star III-17 is derived by fitting synthetic spectra to the spectrum observed in the wavelength region λλ475–580 nm. We derived an overall metallicity of [M/H] = –0.2⁺⁰’²₋₀‚₄ , therefore approximately solar, whereas there may be an evidence for a CNO overabundance. Further observations of individual stars in NGC 6553 are necessary in order to definitely establish its metallicity
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