Presolar grains from novae: their isotopic ratios and radioactivities

Five SiC and two graphite presolar grains exhibit isotopic ratios characteristic of ONe nova nucleosynthesis: low C-12/C-13 (4-9), low N-14/N-15 (5-20), high Al-26/Al-27, high Si-30/Si-28 (2 X solar) with close-to-normal Si-29/Si-28. The upper limit of Ne-20/Ne-22 (<0.01) of one graphite grain suggests that the Ne-22 excess is due to the decay of Na-22. In order to achieve the isotopic ratios of the grains, however, synthesized material during nova explosion had to be mixed with isotopically close-to-solar material, which should consist of more than 95% of the mix. (C) 2002 Elsevier Science BY. All rights reserved.