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Extreme excesses of $^{13}C$ ($^{12}C$/$^{13}C$<10) and $^{15}N$($^{14}N$/$^{15}N$<20) in rare presolar SiC grains have been considereddiagnostic of an origin in classical novae, though an origin in core collapsesupernovae (CCSNe) has also been proposed. We report C, N, and Si isotope datafor 14 submicron- to micron-sized $^{13}C$- and $^{15}N$-enriched presolar SiCgrains ($^{12}C$/$^{13}C$<16 and $^{14}N$/$^{15}N$<~100) from Murchison, andtheir correlated Mg-Al, S, and Ca-Ti isotope data when available. These grainsare enriched in $^{13}C$ and $^{15}N$, but with quite diverse Si isotopicsignatures. Four grains with $^{29,30}Si$ excesses similar to those of type CSiC grains likely came from CCSNe, which experienced explosive H burningoccurred during explosions. The independent coexistence of proton- andneutron-capture isotopic signatures in these grains strongly supportsheterogeneous H ingestion into the He shell in pre-supernovae. Two of the sevenputative nova grains with $^{30}Si$ excesses and $^{29}Si$ depletions showlower-than-solar $^{34}S$/$^{32}S$ ratios that cannot be explained by classicalnova nucleosynthetic models. We discuss these signatures within the CCSNscenario. For the remaining five putative nova grains, both nova and supernovaorigins are viable because explosive H burning in the two stellar sites couldresult in quite similar proton-capture isotopic signatures. Three of the grainsare sub-type AB grains that are also $^{13}C$ enriched, but have a range ofhigher $^{14}N$/$^{15}N$. We found that $^{15}N$-enriched AB grains(~50<$^{14}N$/$^{15}N$<~100) have distinctive isotopic signatures compared toputative nova grains, such as higher $^{14}N$/$^{15}N$, lower$^{26}Al$/$^{27}Al$, and lack of $^{30}Si$ excess, indicating weakerproton-capture nucleosynthetic environments.

Stellar Origins of Extremely $^{\text{13}}C$- and $^{15}N$-enriched Presolar SiC Grains: Novae or Supernovae?