Presolar grains from novae

Five SiC grains and one graphite grain have low C-12/C-13 (4 - 9; solar 89) and N-14/N-15 (5 - 20; solar 272) ratios, high Al-26/Al-27 ratios (greater than or equal to0.01) and large Si-30 excesses (up to 2.1xsolar) but close -to-solar Si-29/Si-28 ratios. These signatures strongly suggest a nova orig in for these grains. The Si isotopic ratios indicate that they formed in ON e novae with white dwarf masses of greater than or equal to 1.25M(circle do t). In order to reproduce the isotopic composition of the grains, however, the ejecta have to be mixed with material of close-to-solar isotopic compos ition before grain formation.