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Title: Impact of the uncertainty in α-captures on {sup 22}Ne on the weak s-process in massive stars

Massive stars at solar metallicity contribute to the production of heavy elements with atomic masses between A = 60 and A = 90 via the so-called weak s-process (which takes place during core He and shell C burning phases). Furthermore, recent studies have shown that rotation boosts the s-process production in massive stars at low metallicities, with a production that may reach the barium neutron-magic peak. These results are very sensitive to neutron source and neutron poison reaction rates. For the weak s-process, the main neutron source is the reaction {sup 22}Ne(α,n){sup 25}Mg, which is in competition with {sup 22}Ne(α,γ){sup 26}Mg. The uncertainty of both rates strongly affects the nucleosynthesis predictions from stellar model calculations. In this study, we investigate the impact of the uncertainty in α-captures on {sup 22}Ne on the s-process nucleosynthesis in massive stars both at solar and at very low metallicity. For this purpose, we post-process, with the Nugrid mppnp code, non-rotating and rotating evolutionary models 25M{sub ⊙} stars at two different metallicities: Z = Z{sub ⊙} and Z = 10{sup −5}Z{sub ⊙}, respectively. Our results show that uncertainty of {sup 22}Ne(α,n){sup 25}Mg and {sup 22}Ne(α,γ){sup 26}Mg rates have a significant impact on the final elementalmore » production especially for metal poor rotating models. Beside uncertainties in the neutron source reactions, for fast rotating massive stars at low metallicity we revisit the impact of the neutron poisoning effect by the reaction chain {sup 16}O(n,γ){sup 17}O(α,γ){sup 21}Ne, in competition with the {sup 17}O(α,n){sup 20}Ne, recycling the neutrons captured by {sup 16}O.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ; ; ;  [7]
  1. Astrophysics group, EPSAM, Keele University, Keele, ST5 1BH, UK and NuGrid Project (United Kingdom)
  2. Astrophysics group, EPSAM, Keele University, Keele, ST5 1BH, UK and Kavli IPMU (WPI), University of Tokyo, Kashiwa, 277-8583 (Japan)
  3. NuGrid Project and Department of Physics, University of Basel, Basel, CH-4056 (Switzerland)
  4. NuGrid Project and Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P5C2 (Canada)
  5. NuGrid Project and Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)
  6. Dipartiment di Scienze Fisiche, Universita di Napoli Federico II, Napoli (Italy)
  7. Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)
Publication Date:
OSTI Identifier:
22280712
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1594; Journal Issue: 1; Conference: OMEG12: 12. international symposium on origin of matter and evolution of galaxies, Tsukuba (Japan), 18-21 Nov 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALPHA REACTIONS; ASTROPHYSICS; BARIUM; CAPTURE; GIANT STARS; MAGNESIUM 25; MAGNESIUM 26; NEON 20; NEON 21; NEON 22; NEON 22 TARGET; NEUTRON REACTIONS; NEUTRONS; NUCLEAR REACTION KINETICS; NUCLEOSYNTHESIS; OXYGEN 16; OXYGEN 16 TARGET; OXYGEN 17 TARGET; S PROCESS