Strength of the $E_R=127$ keV, ${}^{26}\mathrm{Al}(p,\gamma ){}^{27}\mathrm{Si}$ resonance

We examine the impact of the strength of the $E_R=127$ keV, ${}^{26}\mathrm{Al}\left(p,\gamma \right){}^{27}\mathrm{Si}$ resonance on ${}^{26}\mathrm{Al}$ production in classical nova explosions and asymptotic giant branch (AGB) stars. Thermonuclear ${}^{26}\mathrm{Al}\left(p,\gamma \right){}^{27}\mathrm{Si}$ reaction rates are determined using different assumed strengths for this resonance and representative stellar model calculations of these astrophysical environments are performed using these different rates. Predicted ${}^{26}\mathrm{Al}$ yields in our models are not sensitive to differences in rates determined using zero and a commonly stated upper limit corresponding to $\omega {\gamma }_{\mathrm{UL}}=0.0042$ $\mu \mathrm{eV}$ for this resonance strength. Yields of ${}^{26}\mathrm{Al}$ decrease by 6% and, more significantly, up to 30%, when a strength of $24\times \omega {\gamma }_{\mathrm{UL}}=0.1$ $\mu \mathrm{eV}$ is assumed in the adopted nova and AGB star models, respectively. Given that the value of $\omega {\gamma }_{\mathrm{UL}}$ was deduced from a single, background-dominated ${}^{26}\mathrm{Al}({}^3\mathrm{He},d){}^{27}\mathrm{Si}$ experiment where only upper limits on differential cross sections were determined, we encourage new experiments to confirm the strength of the 127-keV resonance.

Figure 1

Thermonuclear rates of the ${}^{26}\mathrm{Al}(p,\gamma ){}^{27}\mathrm{Si}$ reaction calculated using different assumed strengths (in $\mu \mathrm{eV}$) for the $E_R$ = 127 keV resonance. Rates are shown relative to the rate calculated using a strength of 0.0042 $\mu \mathrm{eV}$. All other parameters for these rate calculations were adopted from Ref. [22].