Presolar Grains from Novae

Abstract

We report the discovery of five SiC grains and one graphite grain isolated from the Murchison carbonaceous meteorite whose major-element isotopic compositions indicate an origin in nova explosions. The grains are characterized by low 12C/13C (4-9) and 14N/15N (5-20) ratios, large excesses in 30Si (30Si/28Si ratios range to 2.1 times solar) and high 26Al/27Al ratios. These isotopic signatures are theoretically predicted for the ejecta from ONe novae and cannot be matched by any other stellar sources. Previous studies of presolar grains from primitive meteorites have shown that the vast majority formed in red giant outflows and supernova ejecta. Although a classical nova origin was suggested for a few presolar graphite grains on the basis of 22Ne enrichments, this identification is somewhat ambiguous since it is based only on one trace element. Our present study presents the first evidence for nova grains on the basis of major element isotopic compositions of single grains. We also present the results of nucleosynthetic calculations of classical nova models and compare the predicted isotopic ratios with those of the grains. The comparison points toward massive ONe novae if the ejecta are mixed with material of close-to-solar composition.Comment: 20 pages, 5 figures, 1 table. ApJ, in pres

Ne ISOTOPES IN INDIVIDUAL PRESOLAR GRAPHITE GRAINS FROM THE MURCHISON METEORITE TOGETHER WITH He, C, O, Mg-Al ISOTOPIC ANALYSES AS TRACERS OF THEIR ORIGINS

“…In contrast, more high-density grains (KFC1 density fraction) bear signatures, e.g., the chemical composition of internal refractory carbides and the isotopic compositions of heavy elements, from AGB stars (e.g., Croat et al 2005;. The isotopic compositions of a few grains are qualitatively consistent with a nova origin (Amari et al 2001a;José & Hernanz 2007).…”

Presolar Grains From Novae: Evidence From Neon and Helium Isotopes in Comet Dust Collections

“…Modern searches for interstellar grains in meteorites and IDPs are carried out for the most part by scanning samples for small "hotspots" of isotopically anomalous H, C, N, O, Mg, Si, and other elements utilizing secondary ion mass spectrometry (SIMS), scanning electron microscopy (SEM), and other analytic techniques with high spatial resolution (e.g., Amari et al 2001;Busemann et al 2009). Instruments of this type, however, cannot detect trace amounts of noble gases.…”

Absolute determination of theNa22(p,γ)Sallaska1, Wrede2, Garcı́a3 et al. 2011Phys. Rev. C255340View full textAdd to dashboardCite

“…This suggests we are now on the verge of being able to detect this signal. In addition, Ne isotopic ratios in some meteoritic presolar graphite grains imply the in-situ decay of 22 Na produced by nucleosynthesis in novae [13,14] and/or supernovae [15].…”