Speaker
Description
Meteoritic isotopic anomalies preserve the isotopic fingerprints of stellar nucleosynthesis before and during Solar System formation. In presolar grains, these signatures can be measured in individual stellar condensates, while bulk meteorite components and leachates record the incomplete mixing of distinct nucleosynthetic carriers in the solar protoplanetary disk. Together, these materials provide some of the most precise laboratory constraints on neutron-capture nucleosynthesis, stellar evolution, and Galactic chemical evolution.
In this invited talk, I will give a broad introduction to meteoritic isotopic anomalies and discuss recent collaborative efforts to revisit several long-standing discrepancies between meteoritic data and asymptotic giant branch star (AGB) predictions. Using updated neutron-capture information from the n_TOF and Back-n facilities together with FRUITY AGB models, we found that several previously unresolved isotope systems can now be brought into good agreement with meteoritic constraints. These include Dy isotopic anomalies in meteorite leachates, Mo–Nb systematics relevant to 94Mo/92Mo in presolar SiC grains, and the 64Ni enrichments of AGB-derived SiC grains.
Although these cases all point toward improved agreement between meteoritic data and AGB nucleosynthesis, the underlying causes of the earlier discrepancies are different. For Dy isotopes, the mismatch was likely amplified by limitations in early meteoritic measurements, including unresolved isobaric interferences. For Ni isotopes in presolar SiC grains, earlier measurements were affected by solar Ni contamination, whereas new Ni isotope data reveal intrinsic AGB signatures consistent with FRUITY predictions when updated 64Ni neutron-capture constraints are used. For the Mo–Nb system, the key issue lies instead in the inaccurate treatment of the temperature-dependent β− decay rate of 94Nb in previous AGB models, which limited the production of 94Mo through the β− decay channel.
I will also discuss how the new Ni isotope measurements of presolar SiC grains extend beyond AGB nucleosynthesis. In particular, correlated 60Ni enrichments in selected grains provide isotopic evidence for local Type Ia supernova pollution of the parent molecular clouds from which their parent stars formed. These results show how meteoritic isotopic anomalies can be used not only to refine nuclear inputs and stellar models, but also to trace the evolving contributions of different stellar sources to Galactic chemical evolution.