Could SiC A+B grains have originated in a post-AGB thermal pulse?
  The carbon and nitrogen isotopic ratios of pre-solar SiC grains of type A+B suggest a proton-limited nucleosynthetic process as encountered, for instance, during the very late thermal pulse of post-AGB stars. We study the nuclear processes during this phase and find carbon and nitrogen isotopic ratios which can reproduce those of A+B grains. These results are still preliminary because they depend on uncertain factors such as the details of mixing during the post-AGB thermal pulse, the rates of some nuclear reactions, and the assumptions on mixing during the progenitor AGB phase. 
Falk Herwig (1), Sachiko Amari (2), Maria Lugaro (3) and Ernst Zinner   (2) ((1) University of Victoria, Canada (2) Washingt...