S. Bisterzo^1,2, C. Travaglio^1,5, R. Gallino^2,5, M. Wiescher³ and F. Käppeler⁴

¹INAF-Astrophysical Observatory Turin, Turin, Italy
²Department of Physics, University of Turin, Turin, Italy
³Joint Institute for Nuclear Astrophysics (JINA), Department of Physics, University of Notre Dame, Notre Dame IN, USA
⁴Karlsruhe Institute of Technology, Campus Nord, Institut für Kernphysik, Karlsruhe, Germany
⁵B2FH Association-c/o Strada Osservatorio 20, I-10023 Turin, Italy.

We study the s-process abundances (A  90) at the epoch of the solar system formation. Asymptotic giant branch yields are computed with an updated neutron capture network and updated initial solar abundances. We confirm our previous results obtained with a Galactic chemical evolution (GCE) model: (1) as suggested by the s-process spread observed in disk stars and in presolar meteoritic SiC grains, a weighted average of s-process strengths is needed to reproduce the solar s distribution of isotopes with A > 130; and (2) an additional contribution (of about 25%) is required in order to represent the solar s-process abundances of isotopes from A = 90 to 130. Furthermore, we investigate the effect of different internal structures of the ¹³C pocket, which may affect the efficiency of the ¹³C(α, n)¹⁶O reaction, the major neutron source of the s process. First, keeping the same ¹³C profile adopted so far, we modify by a factor of two the mass involved in the pocket; second, we assume a flat ¹³C profile in the pocket, and we test again the effects of the variation of the mass of the pocket. We find that GCE s predictions at the epoch of the solar system formation marginally depend on the size and shape of the ¹³C pocket once a different weighted range of ¹³C-pocket strengths is assumed. We obtain that, independently of the internal structure of the ¹³C pocket, the missing solar system s-process contribution in the range from A = 90 to 130 remains essentially the same.

Reference
Bisterzo S. Travaglio C, Gallino R, Wiescher M and Käppeler F (2014) Galactic Chemical Evolution and Solar s-process Abundances: Dependence on the 13C-pocket Structure. The Astrophysical Journal 787:10.
[doi:10.1088/0004-637X/787/1/10]

Link to Article