A new ultra metal-deficient star : CS 22876-32 (alpha 1950 = 00h05m04.8, delta 1950 = -35 47' 58").

The chemical composition of blue spectra of the halo stars CS 22876 - 32 and CD - 38 deg 245 is analyzed. Observations and data reduction are outlined, and the method of deriving abundances is presented, along with all the lines of the stars analyzed in the study. It is pointed out that CS 22876 - 32 is the most metal-deficient dwarf ever analyzed, and that magnesium is overabundant with respect to iron. The increase in the overabundance of magnesium could be related to the different type of supernova involved in the nucleosynthesis of two elements, which suggests that at the beginning the nucleosynthesis processes were dominated by massive stars. It is also noted that the ratios of other alpha-elements to iron are overabundant in these stars, and the abundances of Al and Na behave like iron. Both stars demonstrate an internal consistency in the relative abundances, suggesting a complete mixing of the gas from which they are formed.