Spectroscopic Studies of Extremely Metal‐poor Stars with the Subaru High‐Dispersion Spectrograph. IV. The α‐Element–Enhanced Metal‐poor Star BS 16934−002

A detailed elemental abundance analysis has been carried out for the verymetal-poor ([Fe/H]=-2.7) star BS16934-002, which was identified in our previouswork as a star exhibiting large overabundances of Mg and Sc. A comparison ofthe abundance pattern of this star with that of the well-studied metal-poorstar HD122563 indicates excesses of O, Na, Mg, Al, and Sc in BS16934-002. Ofparticular interest, no excess of C or N is found in this object, in contrastto CS22949-037 and CS29498-043, two previously known carbon-rich, extremelymetal-poor stars with excesses of the alpha elements. No establishednucleosynthesis model exists that explains the observed abundance pattern ofBS16934-002. A supernova model, including mixing and fallback, assuming severemass loss before explosion, is discussed as a candidate progenitor ofBS16934-002.Comment: 34 pages, 4 tables, 7 figures, Astrophysical Jounal, in pres