The $^{13}C$-pockets in AGB Stars and Their Fingerprints in Mainstream SiC Grains

We identify three isotopic tracers that can be used to constrain the $^{13}C$-pocket and show the correlated isotopic ratios of Sr and Ba in single mainstream presolar SiC grains. These newly measured data can be explained by postprocess AGB model calculations with large $^{13}C$-pockets with a range of relatively low $^{13}C$ concentrations, which may suggest that multiple mixing processes contributed to the $^{13}C$-pocket formation in parent AGB stars.