Publ. Astron. Soc. Pac., 111, 817-828 (1999/July-0)
Abundances in the metal-poor common proper motion star BD +00°2058A.
Abstract (from CDS):
Like two other metal-poor, late-type field stars showing odd abundance ratios suggestive of accreted origin, BD +00°2058A has a substantial apogalactocentric distance, reaches a large maximum height above the Galactic plane, and is a member of a common proper motion system. To examine whether such wide pairs might have a common origin in accreted subsystems, we present detailed abundances in BD +00°2058A derived from high signal-to-noise, high-resolution optical spectroscopy. Using spectroscopically derived parameters, we find [Fe/H]=-1.16±0.07, a factor of 2-4 larger than previous (but less direct) estimates. We find the α-element, iron-peak, and n-capture abundances to be unremarkable compared with other field stars of similar [Fe/H]. The derived Li abundance, logN(Li)=2.53, is large compared with otherwise similar stars; the normal n-capture abundances and upper limits to 6Li/7Li provide no evidence of Li enrichment from Li-rich asymptotic giant branch star material or spallation. Interestingly, the [C/Fe] and [Na/Fe] ratios appear to be ∼0.3 dex lower and higher, respectively, than otherwise similar stars. This might point to Li enrichment by contaminating material having undergone ``cool bottom processing'', but the lack of radial velocity variations provides no evidence of a close companion. Comparison with theoretical isochrones suggests a distance of 150 pc, which is in better agreement with two previous studies' estimates of the distance of the fainter wide companion; kinematically based population classifications based on this distance are ambiguous. Finally, we draw attention to the importance of different, but reasonable, choices of Fe I gf-values in our (and other) analyses.
Stars: Binaries: General - Galaxy: Abundances - Galaxy: Halo - Stars: Abundances - stars: individual (BD +00 2058A) - Stars: Late-Type - Stars: Population II
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