We discuss the current status of the sample of Lithium abundances in extremely metal poor ( EMP ) turn-off ( TO ) stars collected by our group , and compare it with the available literature results .
In the last years , evidences have accumulated of a progressive disruption of the Spite plateau in stars of extremely low metallicity .
What appears to be a flat , thin plateau above [ Fe/H ] \sim -2.8 turns , at lower metallicities , into a broader distribution for which the plateau level constitutes the upper limit , but more and more stars show lower Li abundances .
The sample we have collected currently counts abundances or upper limits for 44 EMP TO stars between [ Fe/H ] =-2.5 and -3.5 , plus the ultra-metal poor star SDSS J102915+172927 at [ Fe/H ] =-4.9 .
The “ meltdown ” of the Spite plateau is quite evident and , at the current status of the sample , does not appear to be restricted to the cool end of the effective temperature distribution .
SDSS J102915+172927 displays an extreme Li depletion that contrasts with its otherwise quite ordinary set of [ X/Fe ] ratios .