Speaker: Dr. Kiana Setoodehnia
McMaster University, Canada
The dominant nova nucleosynthetic path followed by the thermonuclear runaway on the surface of the white dwarf is very sensitive to the chemical composition of the white dwarf, the extent to which the convective mixing occurs, and the thermal history of the envelope. Such details can be partially obtained via the laboratory analysis of the Si isotopic abundance ratios (29Si/28Si and 30Si/28Si) in presolar grains of nova origin. To estimate the Si isotopic abundances in presolar grains, it is critical to know the rates of the thermonuclear reactions which affect the Si production and destruction in novae. Two such reactions are 29P(p,γ)30S and 30P(p, γ)31S. The 30P(p, γ)31S reaction rate also plays an important role in understanding how the nova nucleosynthetic path is shifted to the A > 30 mass region. At nova temperature range (0.1 – 0.4 GK), the 29P(p, γ)30S reaction rate is thought to be dominated by two low energy proton-unbound 3+ and 2+ resonances, whose properties were mostly unknown until the present work; while the 30P(p, γ)31S reaction rate is dominated by the resonances corresponding to the excitation energies in the range of 6 – 7 MeV in 31S. Despite recent progress in determining the properties of the 31S resonances, some of the known states lack firm spin-parity assignments, and the existence of unobserved resonances cannot yet be precluded. We investigated the level structure of 30S via the 32S(p,t)30S and 28Si(3He,n γ)30S reactions and that of 31S via the 32S(p,d)31S reaction. In my talk, Dr. Setoodehnia will discuss these experiments and their results, and present astrophysical implications.
Originally published at physics.nd.edu.