Nitrogen isotope ratios models

Figure 2.6 Carbon- and nitrogen-isotopic compositions of presolar SiC grains. Predictions from stellar models are shown for comparison. Solar metallicity AGB star models Nollett et al. (2003), Type II SN Rauscher et al. (2002), novae Jose et al. (2004). For data sources see Lodders Amari (2005) Zinner (2007). Note that for the solar 14N/15N ratio the value inferred for Jupiter s atmosphere is shown.

J 5). Average analytical variability of sample preparation and stable carbon isotope ratio analysis is +0.2 (1 ). A Carlo-Erba Model 1106 Elemental Analyzer was employed to determine percent organic carbon and nitrogen in each sediment sample. Analytical variation of sample analysis is 20 (17). 

Theoretical modeling provides strong evidence that most presolar silicon carbide grains come from 1.5 to 3 M stars. As discussed in Chapter 3, stellar modeling of the evolution of the CNO isotopes in the envelopes of these stars makes clear predictions about the 12C/13C, 14N/15N, 170/160,180/160 ratios as a star evolves. For example, in the envelopes of low- to intermediate-mass stars of solar composition, the 12C/13C ratio drops to 40 (from a starting value of 89), and 14N/15N increases by a factor of six as carbon and nitrogen processed by... 

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