Spectroscopic studies of extremely metal-poor stars with the subaru high-dispersion spectrograph. IV. The alpha-element-enhanced metal-poor star bs 16934-002

Aoki, W.; Honda, S.; Beers, T. C.; Takada-Hidai, M.; Iwamoto, N.; Tominaga, N.; Umeda, H.; Nomoto, K.; Norris, J. E. and Ryan, S. G. (2007). Spectroscopic studies of extremely metal-poor stars with the subaru high-dispersion spectrograph. IV. The alpha-element-enhanced metal-poor star bs 16934-002. Astrophysical Journal, 660(1) pp. 747–761.

DOI: https://doi.org/10.1086/512601

URL: http://www.iop.org/EJ/abstract/0004-637X/660/1/747

Abstract

detailed elemental abundance analysis has been carried out for the very metal-poor (Fe/H = -2.7)star BS 16934-002, which was identified in our previous work as a star exhibiting large overabundances of Mg and Sc. A comparison of the abundance pattern of this star with that of the well-studied metal-poor star HD 122563 indicates excesses of O, Na, Mg, Al, and Sc in BS 16934 002. Of particular interest, no excess of C or N is found in this object, in contrast to CS 22949-037 and CS 29498-043, two previously known carbon-rich, extremely metal-poor stars with excesses of the alpha-elements. No established nucleosynthesis model exists that explains the observed abundance pattern of BS 16934-002. A supernova model, including mixing and fallback and assuming severe mass loss before explosion, is discussed as a candidate progenitor of BS 16934-002.