Strontium Isotopic Composition in Individual Circumstellar Silicon Carbide Grains: A Record ofs-Process Nucleosynthesis

Abstract
Twenty six individual circumstellar SiC grains extracted from the Murchison meteorite were analyzed for their strontium isotopic compositions by resonant ionization mass spectrometry. Large abundance deficits were found for the p-process isotope 84Sr. The measured grains had 87Sr/86Sr ratios indistinguishable from the primordial solar value, but several grains differed in their 88Sr/86Sr ratios as a consequence of the branch point at 85Kr. The Sr isotopic data are consistent with s-process nucleosynthesis at moderate neutron densities.