Lithium abundances in metal-poor stars^*

I. New observations

¹ Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain
² Consejo Superior de Investigaciones Científicas, Spain
³ Astronomy Department, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720, U.S.A.
⁴ Observatoire de Paris, DASGAL, URA 335 du CNRS, 61 Av. de l'Observatoire, F-75014 Paris, France

Send offprint request to: R. Rebolo (rrl@iac.es)

Received: 23 January 1998
Accepted: 1 March 1999

Abstract

We present the lithium measurements of a continuing programme of light element abundances in metal-poor stars. New equivalent widths of the Li i  nm resonance line in 67 metal-poor stars covering the metallicity range -3.5 ≤ [Fe/H] ≤ -0.4 are reported. For about half of this sample, the observations presented here represent the first measurement of the Li i line. The sample allowed a statistical comparison with previous measurements from other authors and a study of the consistency and reliability of the quoted error bars. This paper shows that for most of the stars these error bars are good estimates of the true uncertainties associated with the determination of the equivalent widths of the 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 cases, other sources of uncertainty not properly taken into account (binarity effects, cosmic rays, imperfect flat-field correction, continuum determination, etc.) could also be important. Conclusions on the possible lithium abundance trends versus effective temperature or metallicity and on any intrinsic scatter should be treated cautiously until their robustness vis-à-vis these additional uncertainties is proved.