Impact of Newly Measured Nuclear Reaction Rates on $^{26}$Al Ejected Yields from Massive Stars

TL;DR

This study evaluates how recent high-precision measurements of nuclear reaction rates affect the predicted yields of $^{26}$Al from massive stars and compares these yields to early solar system isotope ratios.

Contribution

It provides updated nucleosynthesis predictions using new reaction rates and assesses their impact on $^{26}$Al yields and early solar system isotopic compositions.

Findings

Total $^{26}$Al yields vary by a factor of ~3 with new rates.

New reaction rates significantly alter predicted radionuclide abundances.

Massive star models alone cannot explain all early solar system isotope ratios.

Abstract

Over the last three years, the rates of all the main nuclear reactions involving the destruction and production of $^{26}$Al in stars ($^{26}$Al(n, p)$^{26}$Mg, $^{26}$Al(n, $\alpha$)$^{23}$Na, $^{26}$Al(p, $\gamma$)$^{27}$Si and $^{25}$Mg(p, $\gamma$)$^{26}$Al) have been re-evaluated thanks to new high-precision experimental measurements of their cross sections at energies of astrophysical interest, considerably reducing the uncertainties in the nuclear physics affecting their nucleosynthesis. We computed the nucleosynthetic yields ejected by the explosion of a high-mass star (20 Msun, Z = 0.0134) using the FRANEC stellar code, considering two explosion energies, 1.2 10$^{51}$ erg and 3 10$^{51}$ erg. We quantify the change in the ejected amount of $^{26}$Al and other key species that is predicted when the new rate selection is adopted instead of the reaction rates from the STARLIB nuclear library. Additionally, the ratio of our ejected yields of 26Al to those of 14 other short-lived radionuclides (36Cl, 41Ca, 53Mn, 60Fe, 92Nb, 97Tc, 98Tc, 107Pd, 126Sn, 129I, 36Cs, 146Sm, 182Hf, 205Pb) are compared to early solar system isotopic ratios, inferred from meteorite measurements. The total ejected 26Al yields vary by a factor of ~3 when adopting the new rates or the STARLIB rates. Additionally, the new nuclear reaction rates also impact the predicted abundances of short-lived radionuclides in the early solar system relative to $^{26}$Al. However, it is not possible to reproduce all the short-lived radionuclide isotopic ratios with our massive star model alone, unless a second stellar source could be invoked, which must have been active in polluting the pristine solar nebula at a similar time of a core-collapse supernova.