Aluminum Abundances, Deep Mixing, and the Blue-Tail Second- Parameter Effect in the Globular Clusters M3 and M1 3

2000 ◽  
Vol 120 (3) ◽  
pp. 1364-1383 ◽  
Author(s):  
Robert M. Cavallo ◽  
Neil M. Nagar
Keyword(s):  
Globular Clusters ◽  
Deep Mixing

scholarly journals Abundance Ratios in Metal-Poor Globular Clusters: Deep Mixing and its Effect on Stellar Populations of the Galactic Halo

1998 ◽  
Vol 11 (1) ◽  
pp. 53-57
Author(s):  
Robert P. Kraft
Keyword(s):  
Globular Clusters ◽  
Galactic Halo ◽  
Light Element ◽  
Asymptotic Giant Branch ◽  
Proton Capture ◽  
Low Mass Stars ◽  
Element Abundances ◽  
Deep Mixing ◽  
Low Mass ◽  
Red Giant

Only a bit more than 25 years ago, it seemed possible to assume that all Galactic globular clusters were chemically homogeneous. There were indications that star-to-star Fe abundance variations existed in ω Cen, but this massive cluster appeared to be unique. Following Osborn’s (1971) initial discovery, Zinn’s (1973) observation that M92 asymptotic giant branch (AGB) stars had weaker G-bands than subgiants with equivalent temperatures provided the first extensive evidence that there might be variations in the abundances of the light elements in an otherwise “normal” cluster. Since then star-to-star variations in the abundances of C, N, O, Na, Mg and Al have been observed in all cases in which sample sizes have exceeded 5-10 stars, e.g., in clusters such as M92, M15, M13, M3, ω Cen, MIO and M5. Among giants in these clusters one finds large surface O abundance differences, and these are intimately related to differences of other light element abundances, not only of C and N, but also of Na, Mg and Al (cf. reviews by Suntzeff 1993, Briley et al 1994, and Kraft 1994). The abundances of Na and O, as well as Al and Mg, are anticorrelated. Prime examples are found among giants in M15 (Sneden et al 1997), M13 (Pilachowski et al 1996; Shetrone 1996a,b; and Kraft et al 1997) and ω Cen (Norris & Da Costa 1995a,b). These observed anticorrelations almost certainly result from proton- capture chains that convert C to N, 0 to N, Ne to Na and Mg to Al in or near the hydrogen fusion layers of evolved cluster stars. But which stars? An appealing idea is that during the giant branch lifetimes of the low-mass stars that we now observe, substantial portions of the stellar envelopes have been cycled through regions near the H-burning shell where proton-capture nucleosynthesis can occur. This so-called “evolutionary” scenario involving deep envelope mixing in first ascent red giant branch (RGB) stars has been studied by Denissenkov & Denissenkova (1990), Langer & Hoffman (1995), Cavallo et al (1996, 1997) and Langer et al (1997). The mixing mechanism that brings proton-capture products to the surface is poorly understood (Denissenkov & Weiss 1996, Denissenkov et al 1997, Langer et al 1997), but deep mixing driven by angular momentum has been suggested (Sweigart & Mengel 1979, Kraft 1994, Langer & Hoffman 1995, Sweigart 1997).

scholarly journals Carbon Abundance Inhomogeneities and Deep Mixing Rates in Galactic Globular Clusters

2019 ◽  
Vol 157 (4) ◽  
pp. 154
Author(s):  
Jeffrey M. Gerber ◽  
Michael M. Briley ◽  
Graeme H. Smith
Keyword(s):  
Globular Clusters ◽  
Deep Mixing ◽  
Carbon Abundance ◽  
Mixing Rates ◽  
Galactic Globular Clusters

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.

The Formation and Evolution of Candidate Young Globular Clusters in NGC 3256

1999 ◽  
Vol 118 (2) ◽  
pp. 752-764 ◽  
Author(s):  
Stephen E. Zepf ◽  
Keith M. Ashman ◽  
Jayanne English ◽  
Kenneth C. Freeman ◽  
Ray M. Sharples
Keyword(s):  
Globular Clusters ◽  
Formation And Evolution

Space Velocities of Globular Clusters. III. Cluster Orbits and Halo Substructure

1999 ◽  
Vol 117 (4) ◽  
pp. 1792-1815 ◽  
Author(s):  
Dana I. Dinescu ◽  
Terrence M. Girard ◽  
William F. van Altena
Keyword(s):  
Globular Clusters

Luminosity Functions for Globular Clusters

1998 ◽  
Vol 509 (1) ◽  
pp. 192-202 ◽  
Author(s):  
Fabio Silvestri ◽  
Paolo Ventura ◽  
Francesca D'Antona ◽  
Italo Mazzitelli
Keyword(s):  
Globular Clusters ◽  
Luminosity Functions
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