ANALYSIS OF 2 CH CN-STRONG VERY METAL-POOR STARS/

Two very metal-deficient stars, BPS CS 22948-27 and BPS CS 29497-34, r ecently identified in the HK objeetive-prism/interference-filter surve y of Beers and collaborators, which exhibit, at low resolution, strong CH and CN bands and metallicities [Fe/H] approximate to -3, have been observed at high spectral resolution and high S/N at the NTT at ESO w ith the EMMI echelle spectrograph. A preliminary analysis of these spe ctra shows that these objects are very unusual. The high-resolution wo rk confirms the very low metallicity of these stars and indicates: (i) effective temperatures T-eff approximate to 4000 It and surface gravi ties log g approximate to 0.0 to 1.5; (ii) a very large overabundance of carbon and nitrogen, by similar to 2 dex with respect to iron; (iii ) a similar overabundance of a few neutron-capture elements, in partic ular Ba, La and Nd, also by similar to 2 dex; (iv) a low isotopic rati o C-12/C-13; (V) a variable radial velocity for one of the stars (CS 2 2948-27). These findings suggest that the two stars are extreme cases of CH stars. The spectra are considerably richer in molecular bands th an the spectrum of the remarkable star CS-22892-52, identified in the same survey and studied by Sneden et al. The determination of the rati o of s-process to r-process elements in these two stars must await obs ervations in the blue spectral region.