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Z. Ma (U. Tennessee), M. W. Guidry (U. Tennessee & ORNL Physics Division*), W. R. Hix (U. Tennessee), M. S. Smith (ORNL Physics Division* & RIBENS Collaboration)
Replace these paragraphs with your abstract. We encourage you to include a sentence acknowledging your funding agency. In a recent study the 30P(p,gamma)31S rate played a crucial role in the synthesis of heavier nuclear species, from Si to Ca, in nova outbursts on ONe White Dwarfs [1]. The adopted rate of this reaction, based on a Hauser-Feshbach calculation [2], has a large uncertainty and could be as much as a factor of 100 too high or too low [3]. In their study, Jose et al.[1] varied the 30P(p,gamma)31S reaction rate within this uncertainty and found that, when rate is reduced by a factor of 100, the synthesis of elements above Si is lowered by a factor ~10 with respect to the values found with the nominal rate. This has important consequences for nova nucleosynthesis, as overproduction of isotopes in the Si to Ca mass region has been observed in the ejecta from some nova explosions (e.g.,[4,5]). While generally valid at higher temperatures, Hauser-Feshbach calculations of the rates at nova temperatures can have large uncertainties. At these temperatures, the rate is more likely dominated by a few individual nuclear resonances. At present there are about 10 31S resonances known above the 30P + p threshold that may contribute to the 30P(p,gamma)31S reaction rate at nova temperatures. The excitation energies of these levels are known but spins and parities (for all but two) are not. We plan to measure the 30P(p,p)30P and 30P(p,gamma)31S reactions at HRIBF to better determine this reaction rate. A detailed description of the experiments will be given. We are also conducting a new nova nucleosynthesis simulation over multiple spatial zones of the exploding envelope to investigate the influence of the 30P(p,gamma)31S reaction rate on nova nucleosynthesis. The results of these calculations will be discussed.
1. Jose , J., Coc, A., Hernanz, M., Astrophys. J., 560, 897(2001).
2. Thielemann, F.-K et al., 1987, Advances in Nuclear Astrophysics, ed. E. Vangioni-Flam ( Gif-sur-Yvette: Editions Frontiere), 525(SMOKER).
3. Iliadis, C. et al., Astrophys. J. Suppl., 134,151(2001).
4. Snijders et al., 1987 Snijders, M. A. J., et al., Mon. Not. Roy. Astron. Soc., 228, 329(1987).
5. Andrea, J., Drechsel, H., Starrfield, S., Astron. Astrophys., 291,869(1994)
*Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.