Mg and Al production in intermediate-mass asymptotic giant branch stars

We study how the production of the magnesium and aluminum isotopes in intermediate mass Asymptotic Giant Branch stars is affected by uncertainties in the Ne-22 + alpha-capture reaction rates. We use new estimates of these rates with smaller uncertainties compared to NACRE and consequently find smaller uncertainties on the production of the magnesium and aluminum isotopes. The production of the aluminum isotopes and in particular the radioactive isotope Al-26 is not greatly affected by variations in the a-capture rates and will be more sensitive to uncertainties in the proton-capture MgAl chain reactions. We compare our results to data from pre-solar spinel grains, where the magnesium isotopic ratios have been accurately measured. (c) 2006 Elsevier B.V. All rights reserved.