Chemical Abundances in the Secondary Star in the Black Hole Binary A0620−00

Using a high resolution spectrum of the secondary star in the black holebinary A0620-00, we have derived the stellar parameters and veiling caused bythe accretion disk in a consistent way. We have used a chi^2 minimizationprocedure to explore a grid of 800 000 LTE synthetic spectra computed for aplausible range of both stellar and veiling parameters. Adopting the best modelparameters found, we have determined atmospheric abundances of Fe, Ca, Ti, Niand Al. The Fe abundance of the star is [Fe/H]=0.14 +- 0.20. Except for Ca, wefound the other elements moderately over-abundant as compared with stars in thesolar neighborhood of similar iron content. Taking into account the smallorbital separation, the mass transfer rate and the mass of the convection zoneof the secondary star, a comparison with element yields in supernova explosionmodels suggests a possible explosive event with a mass cut comparable to thecurrent mass of the compact object. We have also analyzed the Li abundance,which is unusually high for a star of this spectral type and relatively lowmass.Comment: 32 pages, 5 tables and 11 figures, uses rotate.st