Exploring the astrophysical energy range of the Al-27(p, alpha)Mg-24 reaction: A new recommended reaction rate

The Al-26 abundance holds a special role in present-day astrophysics, since it is a probe of active nucleosynthesis in the Galaxy and a valuable constraint of Galactic core-collapse supernovae rate. It is estimated through the detection of the 1809-keV gamma-line of the daughter Mg-26 and from the superabundance of Mg-26 in comparison with the most abundant Mg-24 isotope in meteorites. Accurate knowledge of the reaction rates involving Al-26, its stable counterpart Al-27 and 24Mg is then mandatory. Moreover, these nuclei enter the MgAl cycle playing an important role in the production of Al and Mg isotopes. Recently, high-resolution stellar surveys have shown that the Mg-Al anti-correlation in red giants of globular clusters may hide the existence of multiple stellar populations, and that the relative abundances of Mg isotopes may not show correlation with Al. The common thread running through these astrophysical scenarios is the Al-27(p,alpha)Mg-24 reaction, which is the main Al-27 destruction channel and directly correlates its abundance with the Mg-24 one. Since available reaction rates show an order of magnitude uncertainty owing to the vanishingly small cross section at astrophysical energies, we have applied the Trojan Horse Method to deduce the reaction rate with no need of extrapolation. The indirect measurement made it possible to assess the contribution of the 84-keV resonance and to lower the upper limits on the strength of nearby resonances, with potential important impact for astrophysics. In particular, modifications in the Al-27 and Mg-24 abundances up to ~& nbsp;& nbsp;30% are predicted for intermediate mass stars. (C)& nbsp;2022 The Author(s). Published by Elsevier B.V.& nbsp;& nbsp;