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Title: Code dependencies of pre-supernova evolution and nucleosynthesis in massive stars: evolution to the end of core helium burning

We present a comparison of 15M , 20M and 25M stellar models from three different codes|GENEC, KEPLER and MESA|and their nucleosynthetic yields. The models are calculated from the main sequence up to the pre-supernova (pre-SN) stage and do not include rotation. The GENEC and KEPLER models hold physics assumptions that are characteristic of the two codes. The MESA code is generally more flexible; overshooting of the convective core during the hydrogen and helium burning phases in MESA is chosen such that the CO core masses are consistent with those in the GENEC models. Full nucleosynthesis calculations are performed for all models using the NuGrid post-processing tool MPPNP and the key energy-generating nuclear reaction rates are the same for all codes. We are thus able to highlight the key diferences between the models that are caused by the contrasting physics assumptions and numerical implementations of the three codes. A reasonable agreement is found between the surface abundances predicted by the models computed using the different codes, with GENEC exhibiting the strongest enrichment of H-burning products and KEPLER exhibiting the weakest. There are large variations in both the structure and composition of the models—the 15M and 20M in particular—at the pre-SN stagemore » from code to code caused primarily by convective shell merging during the advanced stages. For example the C-shell abundances of O, Ne and Mg predicted by the three codes span one order of magnitude in the 15M models. For the alpha elements between Si and Fe the differences are even larger. The s-process abundances in the C shell are modified by the merging of convective shells; the modification is strongest in the 15M model in which the C-shell material is exposed to O-burning temperatures and the γ -process is activated. The variation in the s-process abundances across the codes is smallest in the 25M models, where it is comparable to the impact of nuclear reaction rate uncertainties. In general the differences in the results from the three codes are due to their contrasting physics assumptions (e.g. prescriptions for mass loss and convection). The broadly similar evolution of the 25M models gives us reassurance that different stellar evolution codes do produce similar results. For the 15M and 20M models, however, the different input physics and the interplay between the various convective zones lead to important differences in both the pre-supernova structure and nucleosynthesis predicted by the three codes. For the KEPLER models the core masses are different and therefore an exact match could not be expected.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [6] ;  [7]
  1. Univ. of Victoria, BC (Canada); Keele Univ. (United Kingdom)
  2. Keele Univ. (United Kingdom); Univ. of Tokyo (Japan)
  3. Univ. of Basel (Switzerland)
  4. Monash Univ., Melbourne, VIC (Australia); Univ. of Minnesota, Minneapolis, MN (United States). School of Physics and Astronomy; Univ. of Notre Dame, IN (United States)
  5. Keele Univ. (United Kingdom)
  6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  7. Univ. of Victoria, BC (Canada); Univ. of Notre Dame, IN (United States)
Publication Date:
OSTI Identifier:
1240392
Report Number(s):
LA-UR-14-28600
Journal ID: ISSN 0035-8711
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 447; Journal Issue: 4; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Research Org:
Los Alamos National Laboratory (LANL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS Astronomy and Astrophysics