2006/09/28 by Lih‐Sin The, Lih-Sin The, M. F. El Eid +3 · 4 citations
Physics and Astronomy · #Astronomical and nuclear sciences #Astronomy #Astrophysics #Asymptotic giant branch #Carbon fibers #Materials science #Nuclear physics research studies #Nucleosynthesis #Physics #Shell (structure) #Stars #Stellar evolution #Stellar nucleosynthesis #Stellar, planetary, and galactic studies #astro-ph #r-process #s-process
paper · pdf · doi:10.1086/509753
published as Astrophys.J.655:1058-1078,2007 · 52 pages, 16 figures, accepted for publication in ApJ
arxiv created 2006/09/28 · openalex publication_date 2007/01/23 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present a detailed study of s -process nucleosynthesis in massive stars of solar-like initial composition and masses 15, 20, 25, and 30 M ☉ . We update our previous results of s -process nucleosynthesis during the core He burning of these stars and then focus on an analysis of the s -process under the physical conditions encountered during the shell carbon burning. We show that the recent compilation of the 22 Ne(α, n ) 25 Mg rate leads to a remarkable reduction of the efficiency of the s -process during core He burning. In particular, this rate leads to the lowest overproduction factor of 80 Kr found to date during core He burning in massive stars. The s -process yields resulting from shell carbon burning turn out to be very sensitive to the structural evolution of the carbon shell. This structure is influenced by the mass fraction of 12 C attained at the end of core helium burning, which in turn is mainly determined by the 12 C(α,γ) 16 O reaction. The still-present uncertainty in the rate for this reaction implies that the s -process in massive stars is also subject to this uncertainty. We identify some isotopes like 70 Zn and 87 Rb as the signatures of the s -process during shell carbon burning in massive stars. In determining the relative contribution of our s -only stellar yields to the solar abundances, we find it is important to take into account the neutron exposure of shell carbon burning. When we analyze our yields with a Salpeter initial mass function, we find that massive stars contribute at least 40% to s -only nuclei with mass A ≤ 87. For s -only nuclei with mass A > 90, massive stars contribute on average ~7%, except for 152 Gd, 187 Os, and 198 Hg, which contribute ~14%, ~13%, and ~11%, respectively.