Some consequences of the instantaneous Simple model

Another important deviation from constancy in the abundance ratio of elements supposed to be primary is displayed by the ratios Fe/O and [Tc/a-elements in stars, which increase systematically with [Fe/H] (Figs. 8.5,8.6). This is usually attributed to the existence of a substantial contribution to the production of iron found in the younger, more metal-rich stars (like the Sun) by SN la, which take times of the order of a Gyr to complete their evolution and therefore cannot be treated 

Some specific GCE models and related observational data 

According to Eq. (8.6), the primary abundances should increase as the logarithm of the gas fraction, the proportionality coefficient giving another estimate of the yield. For example, from the data in Table 7.9, assuming solar oxygen abundance in the local ISM, the effective yield is between 0.5 and 0.7 Z . Other gas-rich systems in which one may try to test this relationship (which obviously does not apply, 

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Some consequences of the instantaneous Simple model 8.3 Some consequences of the instantaneous Simple model 8.3.1 Estimation of yields... 

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