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Astron. Astrophys. 348, 211-221 (1999)

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6. Concluding remarks

It is presently impossible to refine our conclusions because understanding of Li-depletion, especially of 6Li-depletion, is poor. This is unfortunate as there is a tantalizing hint from the few detections of 6Li with the support of the greater suite of upper limits to the 6Li abundance that the growth of the 6Li abundance in the Galaxy up to the metallicity of the old disk ([Fe/H] [FORMULA]) may have been very slight, a result in conflict with the most recent models of 6Li chemical evolution but in agreement with a model proposed by Yoshii et al. (1997). This tentative suggestion is dependent on the absence of severe 6Li-depletion in our disk stars.

Further progress will need additional observations of 6Li in halo and disk stars. Such observations for extremely metal-poor stars, say [Fe/H] [FORMULA], will require a high-resolution spectrograph on an extremely large telescope. More common instrumentation will be adequate for expanding the sample of more metal-rich halo and disk stars with a known 6Li abundance and, in this case, a very large sample of stars may be needed to map out the upper envelope to the 6Li vs [Fe/H] relation which with the corresponding 7Li vs [Fe/H] envelope may suffice to determine empirically the evolution of the 7Li/6Li ratio. A by-product of the survey will be measures of the range of 6Li-depletions experienced by low mass stars of differing metallicity that will serve as grist for the theoreticians' mills.

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© European Southern Observatory (ESO) 1999

Online publication: July 16, 1999