Investigation of the 30Si(p,γ)31P Reaction

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  • July 24, 2019
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  • Dermigny, John
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • Abundance anomalies in globular clusters provide strong evidence for multiple stellar populations within each cluster. These populations are usually interpreted as distinct generations, with the currently observed second-generation stars having formed in part from the ejecta of massive, first generation “polluter” stars, giving rise to the anomalous abundance patterns. The precise nature of the polluters and their enrichment mechanism are still unclear. Even so, the chemical abundances measured in second-generation stars within the cluster NGC 2419 have provided insight into this puzzling process. We performed a sensitivity study using Monte Carlo reaction rate network calculations based on a simple enrichment model for NGC 2419. This work suggested four thermonuclear reactions that have a significant impact on the elemental abundances in this cluster. A firm understanding of the astrophysical source of the pollution material is precluded by their large reaction rate uncertainties. In the present study, one of these reactions, 30Si(p,γ)31P, has been investigated at the Laboratory for Experimental Nuclear Astrophysics (LENA). The resonance strengths of the Elab = 433.5 ± 0.3 keV and Elab = 499.5 ± 0.2 keV resonances have been measured. For the former, which was previously unobserved, we obtain ωγ = 88 ± 19 μeV. For the latter, we obtain ωγ = 188 ± 14 meV. This is consistent with the most recent measurement while improving upon the uncertainty. Based on these results, the thermonuclear reaction rate has been re-evaluated. The impact of the new measurements is to lower the reaction rate by a factor of 10 at temperatures important to the study of NGC 2419. The rate uncertainty at these temperatures has been reduced by a factor of 30.
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Advisor
  • Heitsch, Fabian
  • Champagne, Arthur E
  • Longland, Richard
  • Iliadis, Christian
  • Law, Nick
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2019

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