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A. Boden (ISC/Caltech), G. Torres, D. Latham (CfA), M. Pan (MIT)
For the past two years we have been observing a small sample of mildly metal-poor dwarf spectroscopic binaries using long-baseline interferometry with PTI, and high-resolution radial velocity studies with the Harvard-CfA Oakridge Observatory. Herein we present our first preliminary results on two systems: HD 195987 (G 209-25), a 57d period G-dwarf system with an [Fe/H] of -0.49, and HD 9939 (G 34-39), a 25d period K0 IV system with an [Fe/H] of -0.51. We place our mass and absolute magnitude determinations of the components in these binary systems on evolutionary models for metal-poor stars.
HD 195987 is composed of a G9 V primary and a probable K5 V secondary. Because of the significant color difference, the Hipparcos mission was able to detect photocentric motion and estimate a photocentric orbit in this system. Based on our joint interferometric visibility/radial velocity physical orbit solution we find masses of 0.825 ± 0.014 and 0.655 ± 0.009 M\sun for the primary and secondary component masses respectively.
HD 9939 has a slightly evolved K0 IV primary component along with a probable G6 V secondary component. Our physical orbit solution yields mass determinations in this system of 1.080 ± 0.029 and 0.842 ± 0.020 M\sun for the primary and secondary components respectively.