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C.R. James (Anne Arundel Community College)
We have obtained high resolution (R = 40,000 to 60,000), high signal-to-noise (S/N = 100 to 250) spectra of 61 low metallicity, high proper-motion stars in an attempt to determine possible kinematic and chemical correlations in the Galactic halo. We have derived relative abundances for Li, O, Na, Mg, Ca, Ti, Fe, and Ba, with a precision ranging from 0.01 to 0.10. In addition, we have computed new distances and velocity components for our stars, which were used to calculate the stellar orbital parameters Rapo (maximum galactocentric distance), Rperi (minimum galactocentric distance), Zmax (maximum height above the plane), and 3-D eccentricity. The distances employed are in good agreement with Hipparcos parallaxes, when available. Two stars in our sample (G4-36 and BD+80 245) possess extremely unusual abundance signatures. Specifically, we confirm the previous finding that BD+80 245 is extremely alpha-deficient: [Ca, Mg, and Ti/Fe] = -0.17, rather than the typical halo star value of +0.20 to +0.40. In addition, G4-36 also appears to be deficient in Ca and Mg ([Ca/Fe] = -0.24; [Mg/Fe] = -0.08), but possesses an unusually high abundance of Ti ([Ti/Fe] = +0.50). Furthermore, both stars have extremely low Ba abundances: [Ba/Fe] = -0.83 for G4-36 and [Ba/Fe] = -1.27 for BD+80 245. Kinematically, these two stars have highly retrograde orbits as well as large apogalactic distances, possibly indicating that they may have been accreted from dwarf galaxies that have undergone a chemical evolution distinctly different from that of the Galaxy.