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Carbon-rich grains with isotopic anomalies compared to the Sun are found inprimitive meteorites. They were made by stars, and carry the original stellarnucleosynthesis signature. Silicon carbide grains of Type X and C, andlow-density graphites condensed in the ejecta of core-collapse supernovae. Wepresent a new set of models for the explosive He shell and compare them withthe grains showing 12C/13C and 14N/15N ratios lower than solar. In the stellarprogenitor H was ingested into the He shell and not fully destroyed before theexplosion. Different explosion energies and H concentrations are considered. Ifthe SN shock hits the He-shell region with some H still present, the models canreproduce the C and N isotopic signatures in C-rich grains. Hot-CNO cycleisotopic signatures are obtained, including a large production of 13C and 15N.The short-lived radionuclides 22Na and 26Al are increased by orders ofmagnitude. The production of radiogenic 22Ne from the decay of 22Na in the Heshell might solve the puzzle of the Ne-E(L) component in low-density graphitegrains. This scenario is attractive for the SiC grains of type AB with 14N/15Nratios lower than solar, and provides an alternative solution for SiC grainsoriginally classified as nova grains. Finally, this process may contribute tothe production of 14N and 15N in the Galaxy, helping to produce the 14N/15Nratio in the solar system.

Carbon-rich presolar grains from massive stars. Subsolar 12C/13C and 14N/15N ratios and the mystery of 15N