scholarly journals Rubidium and Lead Abundances in Giant Stars of the Globular Clusters M4 and M5

2008 ◽  
Vol 673 (2) ◽  
pp. 854-863 ◽  
Author(s):  
David Yong ◽  
David L. Lambert ◽  
Diane B. Paulson ◽  
Bruce W. Carney
Keyword(s):  
Globular Clusters ◽  
Giant Stars

scholarly journals A Comparison Between the Relative Heavy Metal Abundance of the Extreme Halo Field Stars and Giant Stars of Globular Clusters

1978 ◽  
Vol 80 ◽  
pp. 169-172
Author(s):  
M. Spite ◽  
F. Spite
Keyword(s):  
Heavy Metal ◽  
Chemical Composition ◽  
Globular Clusters ◽  
Giant Stars ◽  
The Galaxy ◽  
Metal Abundance

Until very recently, estimates of the chemical composition at early epochs of the Galaxy were made through the analysis of halo field stars. Recently, however some medium dispersion studies of stars in globular clusters have appeared. It would be expected that both approaches would lead to identical results. However, a quick glance at the literature gives the opposite impression.

scholarly journals Constant light element abundances suggest that the extended P1 in NGC 2808 is not a consequence of CNO-cycle nucleosynthesis

2019 ◽  
Vol 485 (3) ◽  
pp. 4128-4133 ◽  
Author(s):  
I Cabrera-Ziri ◽  
C Lardo ◽  
A Mucciarelli
Keyword(s):  
Mass Fraction ◽  
Globular Clusters ◽  
Light Element ◽  
Complete Characterization ◽  
Alternative Mechanism ◽  
Abundance Pattern ◽  
Element Abundances ◽  
Chemical Enrichment ◽  
Giant Stars ◽  
Cno Cycle

Abstract Recent photometric results have identified a new population among globular cluster stars. This population, referred to as the ‘extended P1', has been suggested to be the manifestation of a new abundance pattern where the initial mass fraction of He changes among cluster stars that share the same CNO values. The current paradigm for the formation of the multiple stellar populations in globular clusters assumes that variations in He are the product of chemical ‘enrichment’ by the ashes of the CNO-cycle (which changes He and other elements like C, N and O simultaneously). We obtained MIKE@Magellan spectra of six giant stars in NGC 2808, a cluster with one of the strongest examples of the extended P1 population. We provide the first complete characterization of the light elements abundances for the stars along a significant range of the extended P1 photometric group. The stars from our sample appear to be homogeneous in C, N, O, Na, Mg and Al. The lack of a significant change in these products of the CNO-cycle suggests that unlike the rest of the populations identified to date, the photometric changes responsible for the extended P1 feature are a consequence of an alternative mechanism. Our measurements are consistent with the interpretations where the changes of the He mass fraction among these stars could be a consequence of p–p chain nucleosynthesis (which could increase the He in stars without affecting heavier elements). Having said that, direct measurements of He are necessary to conclude if variations of this element are present among extended P1 stars.

scholarly journals Insights into the s-process and r-process as revealed by globular clusters

2009 ◽  
Vol 5 (S265) ◽  
pp. 54-56
Author(s):  
D. Yong ◽  
A. I. Karakas ◽  
D. L. Lambert ◽  
A. Chieffi ◽  
M. Limongi
Keyword(s):  
Relative Abundance ◽  
Neutron Capture ◽  
Globular Clusters ◽  
Giant Stars ◽  
The Mean ◽  
R Process ◽  
Process Material

AbstractWe present abundance measurements for a large number of neutron-capture elements in giant stars of the globular clusters M4, M5, and M13. The relative abundance ratios differ between all three clusters. For all clusters, we find that the mean abundances for the elements from Ba to Hf can be well explained by scaled versions of the solar s- and r-process abundances, albeit with different mixtures of s- and r-process material for each clusters.

scholarly journals Discussion D: Observational problems with Li, Be and B

2009 ◽  
Vol 5 (S268) ◽  
pp. 493-497
Author(s):  
Poul Erik Nissen
Keyword(s):  
Globular Clusters ◽  
Heavy Element ◽  
Main Sequence ◽  
Downward Trend ◽  
Element Abundance ◽  
Theoretical Studies ◽  
Dwarf Stars ◽  
Giant Stars ◽  
Halo Stars ◽  
Solar Type

AbstractIn Discussion D the following problems were addressed: Has 6Li really been detected in the atmospheres of metal-poor halo stars? Is there a downward trend or increased scatter of Li abundances in stars on the ‘Li-plateau’ at metallicities [Fe/H] ≲ −2.5? Are there significant differences of Li abundances in main-sequence, turn-off, and sub-giant stars in globular clusters? Is the Li abundance in solar-type stars related to the presence of planets? How does the Be abundance in dwarf stars increase with the heavy-element abundance, and is there a cosmic scatter in Be at a given [Fe/H]? The discussion of these problems is summarized and some suggestions for future observational and theoretical studies are mentioned.

scholarly journals Facing problems in the determination of stellar temperatures and gravities: Galactic globular clusters

2020 ◽  
Vol 640 ◽  
pp. A87 ◽  
Author(s):  
A. Mucciarelli ◽  
P. Bonifacio
Keyword(s):  
Low Temperatures ◽  
Globular Clusters ◽  
Simple Relation ◽  
Spectroscopic Parameters ◽  
Giant Stars ◽  
Excitation Potential ◽  
Galactic Globular Clusters ◽  
Stellar Temperatures ◽  
Red Giant ◽  
Photometric Scale

We analysed red giant branch stars in 16 Galactic globular clusters, computing their atmospheric parameters both from the photometry and from excitation and ionisation balances. The spectroscopic parameters are lower than the photometric ones and this discrepancy increases with decreasing metallicity, reaching differences of ~350 K in effective temperature and ~1 dex in surface gravity at [Fe/H] ~ –2.5 dex. We demonstrate that the spectroscopic parameters are inconsistent with the position of the stars in the colour-magnitude diagram, providing overly low temperatures and gravities, and predicting that the stars are up to about 2.5 magnitudes brighter than the observed magnitudes. The parameter discrepancy is likely due to inadequacies in the adopted physics; in particular the assumption of a one-dimensional geometry could be the origin of the observed slope between iron abundances and excitation potential that leads to low temperatures. However, the current modelling of 3D/NLTE radiative transfer for giant stars seems to be unable to totally erase this slope. We conclude that the spectroscopic parameters are incorrect for metallicity lower than –1.5 dex and that photometric temperatures and gravities should be adopted for these red giant stars. We provide a simple relation to correct the spectroscopic temperatures in order to put them onto a photometric scale.

On the Luminosity Functions of Giant Stars in Globular Clusters

1972 ◽  
Vol 177 ◽  
pp. 647 ◽  
Author(s):  
John N. Bahcall ◽  
Amos Yahil
Keyword(s):  
Globular Clusters ◽  
Giant Stars ◽  
Luminosity Functions

scholarly journals Infrared Photometry of Globular Cluster Giant Stars: Some Recent Results

1980 ◽  
Vol 85 ◽  
pp. 435-437
Author(s):  
Jay A. Frogel
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Infrared Photometry ◽  
Infrared Observations ◽  
Giant Stars

This talk will briefly summarize some recent results based on infrared observations of giant stars in globular clusters. The program is being carried out jointly with Eric Persson and Judith Cohen of the Hale Observatories.

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