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We present model predictions for the Zr isotopic ratios produced by slowneutron captures in C-rich asymptotic giant branch (AGB) stars of masses 1.25to 4 Msun and metallicities Z=0.01 to 0.03, and compare them to data fromsingle meteoritic stardust silicon carbide (SiC) and high-density graphitegrains that condensed in the outflows of these stars. We compare predictionsproduced using the Zr neutron-capture cross section from Bao et al. (2000) andfrom n_TOF experiments at CERN, and present a new evaluation for theneutron-capture cross section of the unstable isotope 95Zr, the branching pointleading to the production of 96Zr. The new cross sections generally presents animproved match with the observational data, except for the 92Zr/94Zr ratios,which are on average still substantially higher than predicted. The 96Zr/94Zrratios can be explained using our range of initial stellar masses, with themost 96Zr-depleted grains originating from AGB stars of masses 1.8 - 3 Msun,and the others from either lower or higher masses. The 90,91Zr/94Zr variationsmeasured in the grains are well reproduced by the range of stellarmetallicities considered here, which is the same needed to cover the Sicomposition of the grains produced by the chemical evolution of the Galaxy. The92Zr/94Zr versus 29Si/28Si positive correlation observed in the available datasuggests that stellar metallicity rather than rotation plays the major role incovering the 90,91,92Zr/94Zr spread.

astrophysical journal/the astrophysical journal

The impact of updated Zr neutron-capture cross sections and new  asymptotic giant branch models on our understanding of the s process and the  origin of stardust