A New Infrared Array Photometric Survey of Galactic Globular Clusters: A Detailed Study of the Red Giant Branch Sequence as a Step toward the Global Testing of Stellar Models

2000 ◽  
Vol 119 (3) ◽  
pp. 1282-1295 ◽  
Author(s):  
Francesco R. Ferraro ◽  
Paolo Montegriffo ◽  
Livia Origlia ◽  
Flavio Fusi Pecci
Keyword(s):  
Globular Clusters ◽  
Stellar Models ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Infrared Array

scholarly journals Theoretical red-giant branches for globular clusters

1984 ◽  
Vol 105 ◽  
pp. 143-146
Author(s):  
Don A. VandenBerg
Keyword(s):  
Boundary Conditions ◽  
Globular Clusters ◽  
Main Sequence ◽  
Surface Boundary ◽  
Los Alamos ◽  
Surface Boundary Conditions ◽  
Stellar Models ◽  
Red Giant ◽  
Large Grid

VandenBerg (1983a; hereinafter V) has recently computed a large grid of stellar evolutionary sequences from the zero-age main sequence to the base of the red-giant branch (RGB) and carried out extensive comparisons of the associated isochrones with published photometry of globular clusters (GCs). These calculations were based on the latest Los Alamos opacities and, in addition, made use of available model atmospheres for improved surface boundary conditions as well as for the transformation of the stellar models from the (Mbol, log Teff)-to the (Mv, B-V)-plane. In general, very encouraging agreement of the predicted and observed morphologies of cluster C-M diagrams was obtained.

scholarly journals The multipopulation phenomenon in Galactic globular clusters: M4 and M22

2009 ◽  
Vol 5 (S266) ◽  
pp. 326-332
Author(s):  
S. Villanova ◽  
G. Piotto ◽  
A. F. Marino ◽  
A. P. Milone ◽  
A. Bellini ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Data ◽  
Globular Clusters ◽  
Stellar Population ◽  
The Other ◽  
Wide Field ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Process Elements ◽  
Different Characteristics

AbstractWe present an abundance analysis based on high-resolution spectra of red-giant-branch (RGB) stars in the Galactic globular clusters NGC 6121 (M4) and NGC 6656 (M22). Our aim was to study their stellar population in the context of the multipopulation phenomenon recently discovered to affect some globular clusters. Analysis was performed for the following elements: O, Na, Mg, Al, Ca, Fe, Y, and Ba. Spectroscopic data were completed by high-precision wide-field U BV IC ground-based photometry and HST/ACS observations. For M4, we find a well-defined Na–O anticorrelation composed of two distinct groups of stars with significantly different Na and O content. The two groups of Na-rich and Na-poor stars populate two different regions along the RGB. As regards M22, Na and O follow the well-known anticorrelation found in many other GCs. However, at odds with M4, it appears to be continuous without any hint of clumpiness. On the other hand, we identified two clearly separated groups of stars with significantly different abundances of the s-process elements Y, Zr and Ba. The relative numbers of the members of both groups are very similar to the ratio of the stars in the two subgiant branches of M22 recently found by Piotto (2009). The s-element-rich stars are also richer in iron and have higher Ca abundances. This makes M22 the second cluster after ω Centauri where an intrinsic spread in Fe was found. Both spectroscopic and photometric results imply the presence of two stellar populations in M4 and M22, even if both clusters have completely different characteristics.

scholarly journals THE CHEMICAL COMPOSITION OF RED GIANT BRANCH STARS IN THE GALACTIC GLOBULAR CLUSTERS NGC 6342 AND NGC 6366

2016 ◽  
Vol 152 (1) ◽  
pp. 21 ◽  
Author(s):  
Christian I. Johnson ◽  
Nelson Caldwell ◽  
R. Michael Rich ◽  
Catherine A. Pilachowski ◽  
Tiffany Hsyu
Keyword(s):  
Chemical Composition ◽  
Globular Clusters ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Giant Branch Stars

Multiple Stellar Populations: the evolutionary framework

2012 ◽  
Vol 10 (H16) ◽  
pp. 245-246
Author(s):  
Santi Cassisi
Keyword(s):  
Globular Clusters ◽  
Stellar Populations ◽  
Stellar Model ◽  
Photometric Data ◽  
Stellar Systems ◽  
Huge Amount ◽  
Stellar Models ◽  
Galactic Globular Clusters ◽  
New Generation

AbstractIn these last years a huge amount of both spectroscopical and photometric data has provided a plain evidence of the fact that Galactic globular clusters (GCs) host various stellar sub-populations characterized by peculiar chemical patterns. The need of properly interpreting the various observational features observed in the Color-Magnitude Diagrams (CMDs) of these stellar systems requires a new generation of stellar models properly accounting for these chemical peculiarities both in the stellar model computations and in the color - Teff transformations. In this review we discuss the evolutionary framework that is mandatory in order to trace the various sub-populations in any given GC.

scholarly journals The magnitude difference between the main sequence turn off and the red giant branch bump in Galactic globular clusters

2011 ◽  
Vol 527 ◽  
pp. A59 ◽  
Author(s):  
S. Cassisi ◽  
A. Marín-Franch ◽  
M. Salaris ◽  
A. Aparicio ◽  
M. Monelli ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Globular Clusters ◽  
Red Giant ◽  
Magnitude Difference

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.

scholarly journals Lithium on the lower red giant branch of five Galactic globular clusters

2021 ◽  
Author(s):  
C. Aguilera-Gómez ◽  
L. Monaco ◽  
A. Mucciarelli ◽  
M. Salaris ◽  
S. Villanova ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Galactic Globular Clusters ◽  
Red Giant

scholarly journals Galactic globular clusters as a test for very-low-mass stellar models

2000 ◽  
Vol 315 (4) ◽  
pp. 679-688 ◽  
Author(s):  
S. Cassisi ◽  
V. Castellani ◽  
P. Ciarcelluti ◽  
G. Piotto ◽  
M. Zoccali
Keyword(s):  
Globular Clusters ◽  
Low Mass ◽  
Stellar Models ◽  
Galactic Globular Clusters
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