Magnesium isotopes: a tool to understand self-enrichment in Globular Clusters

Abstract

A critical issue in the asymptotic giant branch (AGB) self-enrichment scenario for the formation of multiple populations in Globular Clusters (GCs) is the inability to reproduce the magnesium isotopic ratios, despite the model in principle can account for the depletion of magnesium. In this work we analyze how the uncertainties on the various p-capture cross sections affect the results related to the magnesium content of the ejecta of AGB stars. The observed distribution of the magnesium isotopes and of the overall Mg-Al trend in M13 and NGC 6752 are successfully reproduced when the proton-capture rate by 25Mg at the temperatures 100 MK, in particular the 25Mg(p, gamma)26Alm channel, is enhanced by a factor 3 with respect to the most recent experimental determinations. This assumption also allows to reproduce the full extent of the Mg spread and the Mg-Si anticorrelation observed in NGC 2419. The uncertainties in the rate of the 25Mg(p,gamma)26Alm reaction at the temperatures of interest here leave space for our assumption and we suggest that new experimental measurements are needed to settle this problem. We also discuss the competitive model based on the super massive star nucleosynthesis.

accepted for publication on MNRAS

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Cited by in corpus (11)

• First direct limit on the 334 keV resonance strength in the ${}^{22}$Ne(α,γ)${}^{26}$Mg reaction
• The Cosmic Evolution of Magnesium Isotopes
• The Gaia-ESO Survey: Oxygen abundance in the Galactic thin and thick disks
• Light Element Discontinuities Suggest an Early Termination of Star Formation in the Globular Cluster NGC 6402 (M14)
• Nucleosynthetic yields of Z=$10^{-5}$ intermediate-mass stars
• HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations
• Nucleosynthetic yields of intermediate-mass primordial to extremely metal-poor stars
• Self-enrichment in Globular Clusters: the extreme He-rich population of NGC 2808
• The complex stellar system M 22: constraining the chemical enrichment from AGB stars using magnesium isotope ratios
• `Status update' for the AGB scenario for the formation of multiple populations
• Noble gases Neon and argon: a role for the chemical patterns of multiple populations in globular clusters?