SIMBAD references

Slow neutron captures at A ≳ 85 are mainly guaranteed by the reaction ¹³C(α,n)¹⁶O in asymptotic giant branch (AGB) stars, requiring proton injections from the envelope. These were so far assumed to involve a small mass ( ≲ 10^–3 M_☉), but models with rotation suggest that in such tiny layers excessive ¹⁴N hampers s-processing. Furthermore, s-element abundances in galaxies require ¹³C-rich layers substantially extended in mass ( ≳ 4x10^–3 M_☉). We therefore present new calculations aimed at clarifying those issues and at understanding whether the solar composition helps to constrain the ¹³C "pocket" extension. We show that: (1) mixing "from bottom to top" (as in magnetic buoyancy or other forced mechanisms) can form a ¹³C reservoir substantially larger than assumed so far, covering most of the He-rich layers; (2) on the basis of this idea, stellar models at a fixed metallicity reproduce the main s-component as accurately as before; and (3) they make nuclear contributions from unknown nucleosynthesis processes (LEPP) unnecessary, against common assumptions. These models also avoid problems of mixing at the envelope border and fulfil requirements from C-star luminosities. They yield a large production of nuclei below A = 100, so that ^86, 87^Sr may be fully synthesized by AGB stars, while ⁸⁸Sr, ⁸⁹Y, and ⁹⁴Zr are contributed more efficiently than before. Finally, we suggest tests suitable for providing a final answer regarding the extension of the ¹³C pocket.