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

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] ) 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] , 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.

© European Southern Observatory (ESO) 1999

Online publication: July 16, 1999
helpdesk.link@springer.de