ALIOTTA , M.

Helium burning represents an important stage of stellar evolution as it contributes to the synthesis of key elements such as carbon, through the triple-alfa process, and oxygen, through the 12C(alfa, gamma)16O reaction. It is the ratio of carbon to oxygen at the end of the helium burning stage that governs the following phases of stellar...

The 22Ne(p; γ23Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle affects the synthesis of the elements between 20Ne and 27Al in asymptotic giant branch stars and novae. The 22Ne(p; γ)23Na reaction rate is very uncertain because of a large number of unobserved resonances lying in the Gamow window. At proton energies...

Stardust grains recovered from meteorites provide highprecision snapshots of the isotopic composition of the stellar environment in which they formed1. Attributing their origin to specific types of stars, however, often proves difficult. Intermediate-mass stars of 4–8 solar masses are expected to have contributed a large fraction of meteoritic...

Context. Material processed by the CNO cycle in stellar interiors is enriched in 17O. When mixing processes from the stellar surface reach these layers, as occurs when stars become red giants and undergo the first dredge up, the abundance of 17O increases. Such an occurrence explains the drop of the 16O/17O observed in RGB stars with mass...