1997/11/22 by J. Craig Wheeler, J. C. Wheeler, John J. Cowan +3 · 1 citation
Physics and Astronomy · #Astrophysics #Europium #Gamma-ray bursts and supernovae #Ion #Metallicity #Nuclear physics research studies #Physics #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/311133
16 pages, LaTeX aasms4; to be published in ApJ Letters
arxiv created 1997/11/22 · openalex publication_date 1998/02/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Several circumstantial arguments point to the formation of the third r -process peak at A ~190, near platinum, in stars of mass of ~8-10 M ☉ : (1) the delayed production of europium with respect to iron imposes a timescale that restricts the progenitor stars to M ≲10 M ; (2) the r -process demands a dominant robust mechanism at least for Z ≥56, barium, and above, since the relative abundance pattern of those r -process elements in the low-metallicity stars, [Fe/H] < -2, is consistent with the solar pattern; (3) stars of ~8-10 M ☉ produce nearly identical degenerate O/Ne/Mg cores that collapse because of electron capture; and (4) the resulting low-mass cores may produce both an r -process in a prompt explosion and a subsequent r -process in a neutrino-driven wind. A special case of the r -process singles out low entropies for initial Y e ~ / A , where is the mean atomic number of the seed nuclei and A is the atomic weight of the target. For ≃ 35 and Y e ≃0.18, the A ≃190 peak results in a natural way. The prompt explosion of an O/Ne/Mg core yields a low entropy, S ~15, and a low electron fraction, Y e ≃0.2, and hence may produce a reasonable r -process peak at A ≃190, as well as all of the r -process elements with Z ≥56. The possible differences in the ν-driven wind and associated r -process due to the low-mass neutron stars expected in this mass range are also discussed.