Reaction Rates for 18O( alpha , gamma ) 22Ne, 22Ne( alpha , gamma ) 26Mg, and 22Ne( alpha , n) 25Mg in Stellar Helium Burning and s-Process Nucleosynthesis in Massive Stars
Abstract
New experimental results in O-18(Li-6, d) and Ne-22(Li-6, d) alpha transfer reaction studies have been utilized to calculate the resonance strength of low-energy resonances in the alpha-capture on O-18 and Ne-22. The present results imply a significant increase of the reaction rates for O-18(alpha, gamma)Ne-22 and Ne-22(alpha, gamma)Mg-26. The Ne-22(alpha, n)Mg-25 rate might be strongly enhanced by a possible resonance at 633 keV. The respective uncertainties are presented as a function of temperature. The influence of the proposed reaction rates on the s-process nucleosynthesis during core helium burning has been investigated in the range 15 less than M/solar mass less than 30. The resulting uncertainties are compared to those related to the modeling of core helium burning in massive stars. This comparison indicates that the s-process may be a useful constraint for the evolution and convection in massive stars, provided the persistent problem of the 633 keV resonance in the Ne-22(alpha, n)Mg-25 channel can be solved.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1994
- DOI:
- 10.1086/175004
- Bibcode:
- 1994ApJ...437..396K
- Keywords:
-
- Early Stars;
- Massive Stars;
- Nuclear Fusion;
- Reaction Kinetics;
- Stellar Evolution;
- Stellar Interiors;
- Stellar Models;
- Stellar Physics;
- Convective Flow;
- Helium;
- Mathematical Models;
- Astrophysics;
- NUCLEAR REACTIONS;
- NUCLEOSYNTHESIS;
- ABUNDANCES;
- STARS: EARLY-TYPE;
- STARS: INTERIORS