The second dredge-up The second dredge-up occurs in stars with 4–8 solar masses.As a result of the convective mixing, the outer atmosphere will display the spectral signature of hydrogen fusion: The 12C/ 13C and C/ N ratios are lowered, and the surface abundances of lithium and beryllium may be reduced.

The first dredge-up The first dredge-up occurs when a main-sequence star enters the red-giant branch.Consequently, the fusion products are mixed into the outer layers of the star's atmosphere, where they can be seen in stellar spectra. By definition, during a dredge-up, a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. In these cases where core mixing complicates post-dredge-up surface abundances, uncertainty in other reactions have a secondary but noticeable effect on surface abundances.A dredge-up is any one of several stages in the evolution of some stars. With the new estimates on reaction rate uncertainties by the NACRE compilation, the p-capture reactions 17O(p, α) 14N and 17O(p, γ) 18F have virtually no impact on theoretical predictions for stellar mass 1.5 M solar, where core mixing and subsequent envelope mixing interact. The error of the 16O/ 17O prediction is 10-40 per cent depending on the stellar mass, and is persistently dominated by the comparatively small uncertainty of the 16O(p, γ) 17F reaction. We find that the uncertainty of the 18O(p, α) 15N reaction rate typically causes an error in the theoretical 16O/ 18O ratio of ~= +20/ - 5 per cent.

We include seven reaction rates in our systematic analysis of stellar models with initial masses from 1 to 3 M solar. The reaction rates with uncertainties were taken from the NACRE compilation of Angulo et al.

Such predictions are important to the interpretation of pre-solar Al 2O 3 grains from meteorites. With this approach we reanalyse the dependence of theoretical oxygen isotopic ratio predictions in first dredge-up red giant branch stars in a systematic way. The method combines post-processing nucleosynthesis and mixing calculations with a Monte Carlo scheme. We describe a general yet simple method to analyse the propagation of nuclear reaction rate uncertainties in a stellar nucleosynthesis and mixing context.

Dredge up red giant