Constraining the S factor of 15N(p,g)16O at Astrophysical Energies

TL;DR

This study remeasured the 15N(p,g)16O reaction at astrophysical energies, analyzed the data with R-matrix theory, and provided a more reliable S(0) value crucial for stellar nucleosynthesis models.

Contribution

The paper presents new experimental data and an R-matrix analysis to accurately determine the S factor of 15N(p,g)16O at energies relevant to astrophysics.

Findings

S(0) value of 39.6 keV b determined

Extended energy range measurements from 1800 keV to 130 keV

Analysis highlights interference effects impacting extrapolation

Abstract

The 15N(p,g)16O reaction represents a break out reaction linking the first and second cycle of the CNO cycles redistributing the carbon and nitrogen abundances into the oxygen range. The reaction is dominated by two broad resonances at Ep = 338 keV and 1028 keV and a Direct Capture contribution to the ground state of 16O. Interference effects between these contributions in both the low energy region (Ep < 338 keV) and in between the two resonances (338 <Ep < 1028 keV) can dramatically effect the extrapolation to energies of astrophysical interest. To facilitate a reliable extrapolation the 15N(p,g)16O reaction has been remeasured covering the energy range from Ep=1800 keV down to 130 keV. The results have been analyzed in the framework of a multi-level R-matrix theory and a S(0) value of 39.6 keV b has been found.