Towards a working model for the abundance variations within Globular Clusters stars

Abstract

A popular self--enrichment scenario for the formation of globular clusters assumes that the abundance anomalies shown by the stars in many clusters are due to a second stage of star formation occurring from the matter lost by the winds of massive asymptotic giant branch (AGB) stars. Until today, the modellizations of the AGB evolution by several different groups failed, for different reasons, to account for the patterns of chemical anomalies. Here we show that our own modelling can provide a consistent picture if we constrain the three main parameters which regulate AGB evolution: 1) adopting a high efficiency convection model; 2) adopting rates of mass loss with a high dependence on the stellar luminosity; 3) assuming a very small overshooting below the formal convective regions during the thermal pulse (TP) phase. The first assumption is needed to obtain an efficient oxygen depletion in the AGB envelopes, and the second one is needed to lose the whole stellar envelope within few thermal pulses, so that the sum of CNO elements does not increase too much, consistently with the observations. The third assumption is needed to fully understand the sodium production. We also show that the Mg - Al anticorrelation is explained adopting the higher limit of the NACRE rates for proton captures by Mg25 and Mg26, and the models are consistent with the recently discovered F-Al correlation. Problems remain to fully explain the observed Mg isotopes ratios.

References in corpus (8)

• A helium spread among the main sequence stars in NGC 2808
• Abundances in a Large Sample of Stars in M3 and M13
• Full computation of massive AGB evolution. I. The large impact of convection on nucleosynthesis
• Abundances in giant stars of the globular cluster NGC 6752
• Modelling self-pollution of globular clusters from AGB stars
• Full computation of massive AGB evolution. II. The role of mass loss and cross-sections
• Fluorine Abundance Variations in Red Giants of the Globular Cluster M4 and Early-Cluster Chemical Pollution
• C and N Abundances in Stars At the Base of the Red Giant Branch in M15

Cited by in corpus (39)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• On the self-enrichment scenario of galactic globular clusters: Constraints on the IMF
• Oxygen, Sodium, Magnesium and Aluminium as tracers of the Galactic Bulge Formation
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)
• Nitrogen abundances in giant stars of the globular cluster NGC 6752
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo
• Chemical Evolution of the Galactic Bulge as Derived from High-Resolution Infrared Spectroscopy of K and M Red Giants
• A model for the Globular Cluster extreme anomalies
• Global and non-global parameters of horizontal branch morphology of globular clusters
• High Precision Differential Abundance Measurements in Globular Clusters: Chemical Inhomogeneities in NGC 6752
• Origin of Abundance Inhomogeneity in Globular Clusters
• CNO abundances in the globular clusters NGC 1851 and NGC 6752
• Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• Abundances of lithium, oxygen, and sodium in the turn-off stars of Galactic globular cluster 47 Tuc
• Rubidium and lead abundances in giant stars of the globular clusters M4 and M5
• CNO enrichment by rotating AGB stars in globular clusters
• Impact of a revised ${}^{25}$Mg(p,$\gamma$)${}^{26}$Al reaction rate on the operation of the Mg-Al cycle
• The Chemical Evolution of Globular Clusters I. Reactive Elements and Non-Metals
• Variations in the lithium abundances of turn off stars in the globular cluster 47 Tuc
• Globular Cluster Formation at High Density: A model for Elemental Enrichment with Fast Recycling of Massive-Star Debris
• ${}^{22}$Ne and ${}^{23}$Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for ${}^{22}$Ne(p,$\gamma$)${}^{23}$Na
• Chemical abundances in bright giants of the globular cluster M62 (NGC 6266)
• On the origin of double main-sequence turn-offs in star clusters of the Magellanic Clouds
• On the Delta V_HB_bump parameter in Globular Clusters
• Multiple stellar populations and their evolution in globular clusters: A nucleosynthesis perspective
• Magnesium Isotope Ratios in omega Centauri Red Giants
• Chemical analysis of Asymptotic Giant Branch stars in M62
• Modeling the chemical evolution of Omega Centauri using three-dimensional hydrodynamical simulations
• On the internal pollution mechanisms in the globular cluster NGC 6121 (M4): heavy-element abundances and AGB models
• Lost and found: evidence of Second Generation stars along the Asymptotic Giant Branch of the globular cluster NGC 6752
• The s-Process Enrichment of the Globular Clusters M4 and M22
• Chemical abundance anticorrelations in globular cluster stars: The effect on cluster integrated spectra
• Fluorine Abundance Variations as a Signature of Enhanced Extra Mixing in Red Giants of the Globular Cluster M4
• The Celestial Buffet: multiple populations and globular cluster formation in dwarf galaxies
• Astrophysics in 2006
• Multiple stellar populations and their influence on blue stragglers