Lithium abundances in metal-poor stars I. New observations

We present the lithium measurements of a continuing programme of light elem ent abundances in metal-poor stars. New equivalent widths of the Li I lambd a 670.8 nm resonance line in 67 metal-poor stars covering the metallicity r ange -3.5 less than or equal to [Fe/H] less than or equal to -0.4 are repor ted. For about half of this sample, the observations presented here represe nt the first measurement of the Li I line. The sample allowed a statistical comparison with previous measurements from other authors and a study of th e consistency and reliability of the quoted error bars. This paper shows th at for most of the stars these error bars are good estimates of the true un certainties associated with the determination of the equivalent widths of t he Li I line. However, about 20% of the stars with two or more independent measurements show discrepancies in the Li I equivalent widths; in these cas es, other sources of uncertainty not properly taken into account (binarity effects, cosmic rays, imperfect flat-held correction, continuum determinati on, etc.) could also be important. Conclusions on the possible lithium abun dance trends versus effective temperature or metallicity and on any intrins ic scatter should be treated cautiously until their robustness vis-a-vis th ese additional uncertainties is proved.