The $^{25}$Al$(p,\gamma)^{26}$Si Reaction Rate in Novae

Abstract

The production of 26 Al in novae is uncertain, in part, because of the uncertain rate of the 25 Al(p,γ) 26 Si reaction at novae temperatures. This reaction is thought to be dominated by a longsought 3 + level in 26 Si, and the calculated reaction rate varies by orders of magnitude depending on the energy of this resonance. We present evidence concerning the spin of a level at 5.914 MeV in 26 Si from the 28 Si(p,t) 26 Si reaction studied at the Holifield Radioactive Beam Facility at ORNL. We find that the angular distribution for this level implies either a 2 + or 3 + assignment, with only a 3 + being consistent with the mirror nucleus, 26 Mg. Additionally, we have used the updated 25 Al(p,γ) 26 Si reaction rate in a nova nucleosynthesis calculation and have addressed the effects of the remaining uncertainties in the rate on 26 Al production.