Silicon Isotopic Composition of Mainstream Presolar SiC Grains Revisited: The Impact of Nuclear Reaction Rate Uncertainties

TL;DR

This study investigates how nuclear reaction rate uncertainties affect silicon isotope predictions in presolar grains, showing these uncertainties can explain discrepancies between measurements and models, emphasizing the need for precise nuclear data.

Contribution

The paper demonstrates that nuclear reaction rate uncertainties can account for the silicon isotope correlation discrepancies in presolar SiC grains, linking nuclear physics to astrophysical observations.

Findings

Uncertainties in nuclear reaction rates influence silicon isotope predictions.

Nuclear reaction rate variations can explain the observed data-model discrepancy.

Future precise measurements are crucial for resolving current uncertainties.

Abstract

Presolar grains are stardust particles that condensed in the ejecta or in the outflows of dying stars and can today be extracted from meteorites. They recorded the nucleosynthetic fingerprint of their parent stars and thus serve as valuable probes of these astrophysical sites. The most common types of presolar silicon carbide grains (called mainstream SiC grains) condensed in the outflows of asymptotic giant branch stars. Their measured silicon isotopic abundances are not significantly influenced by nucleosynthesis within the parent star, but rather represents the pristine stellar composition. Silicon isotopes can thus be used as a proxy for galactic chemical evolution. However, the measured correlation of $^{29}$Si/$^{28}$Si versus $^{30}$Si/$^{28}$Si does not agree with any current chemical evolution model. Here, we use a Monte Carlo model to vary nuclear reaction rates within their theoretical or experimental uncertainties and process them through stellar nucleosynthesis and galactic chemical evolution models to study the variation of silicon isotope abundances based on these nuclear reaction rate uncertainties. We find that these uncertainties can indeed be responsible for the discrepancy between measurements and models and that the slope of the silicon isotope correlation line measured in mainstream SiC grains agrees with chemical evolution models within the nuclear reaction rate uncertainties. Our result highlights the importance of future precision reaction rate measurements for resolving the apparent data-model discrepancy.