Reporting from NIC 2012:
Planetary scientists have been analysing stellar dust found in primitive meteorites for around 25 years now. Among the most analysed grains are the SiC grains, which are characterised by their Si, C and N isotope ratios. Among these grains is a sub-group called A+B grains, which showed very low 12C/13C isotope ratios and their stellar source was unclear for years with C-rich AGB stars the most favoured based on nucleosynthetic models.
A group of astronomers now managed to measure the C and N isotope ratios in different groups of AGB stars and found that J-type stars are a very good match for the A+B grains with a complete overlap for the whole range of the C and N isotope ratios confirming the source for these grains for the first time.
At the same time they could show that SC-type AGB stars are needed to explain the low C isotope ratios found in mainstream SiC grains and high mass AGB stars explain the higher C isotope ratios.