A contribution of 26Al to the O-Al anticorrelation in globular cluster red giants

We modify our combined ("deep mixing" plus "primordial") scenario explaining the star-to-star abundance variations in globular cluster red giants in such a way that it conforms with new experimental data: (1) the new and better constrained (NACRE) thermonuclear reaction rates and (2) a discovery of the O-Na anticorrelation in stars below the main-sequence turnoff in the cluster NGC 6752. For the latter, we propose that some main-sequence dwarfs in globular clusters accrete material lost by red giant primary components of close binaries during a common envelope event. As a consequence of the new reaction rates, we are drawn to the conclusion that the anomalies in [Al/Fe] in globular cluster red giants are in fact manifestations of Al-26(8) abundance variations (instead of the stable isotope Al-27) produced by deep mixing. However, Al overabundances observed in some of the subgiants in NGC 6752 are unlikely to be due to the unstable Al-26(g) isotope but have to be the result of the other primordial component of our combined scenario, i.e., intermediate-mass asymptotic giant branch stars. These should also provide the source for enhanced Mg-25, necessary for the Al-26(g) production in deep mixing events.