We investigate the effects of thermonuclear reaction rate variations on 26Al
production in massive stars. The dominant production sites in such events were
recently investigated by using stellar model calculations: explosive
neon-carbon burning, convective shell carbon burning, and convective core
hydrogen burning. Post-processing nucleosynthesis calculations are performed
for each of these sites by adopting temperature-density-time profiles from
recent stellar evolution models. For each profile, we individually multiplied
the rates of all relevant reactions by factors of 10, 2, 0.5 and 0.1, and
analyzed the resulting abundance changes of 26Al. Our simulations are based on
a next-generation nuclear physics library, called STARLIB, which contains a
recent evaluation of Monte Carlo reaction rates. Particular attention is paid
to quantifying the rate uncertainties of those reactions that most sensitively
influence 26Al production. For stellar modelers our results indicate to what
degree predictions of 26Al nucleosynthesis depend on currently uncertain
nuclear physics input, while for nuclear experimentalists our results represent
a guide for future measurements. We tabulate the results of our reaction rate
sensitivity study for each of the three distinct massive star sites referred to
above. It is found that several current reaction rate uncertainties influence
the production of 26Al. Particularly important reactions are 26Al(n,p)26Mg,
25Mg(alpha,n)28Si, 24Mg(n,gamma)25Mg and 23Na(alpha,p)26Mg. These reactions
should be prime targets for future measurements. Overall, we estimate that the
nuclear physics uncertainty of the 26Al yield predicted by the massive star
models explored here amounts to about a factor of 3.Comment: 44 pages, 16 figure
