Fig. 1.

Isotopic ratios of SiC grains from different populations are shown. (a) C and N isotopic ratios. (b) Si isotopic ratios expressed with δ values {δⁱSi/²⁸Si (%₀) = [(ⁱSi/²⁸Si)_grain/(ⁱSi/²⁸Si)_standard − 1] × 1000}. The dotted lines indicate the solar ratios (or the ratio of air for ¹⁴N/¹⁵N). Note that the minor populations of grains have been located for detailed studies, thus grains in these populations are overrepresented in the plots. Real abundances are shown in the legend. The data are from the Presolar Grain Database (http://presolar.wustl.edu/Laboratory_for_Space_Sciences/Presolar_Grain_Database.html) [21].