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R. B. Hindsley (Naval Research Laboratory), W. H. Treseder (Amherst College / Naval Research Laboratory), V. V. Makarov, S. E. Urban (U. S. Naval Observatory)
The high-velocity star HD 187637 (LTT 15789, HIP 97527)is a slightly metal-poor subdwarf that has been studied extensively. The Hipparcos satellite yielded the values V=7.58, B-V = 0.54, proper motion = 0.205 arcsec/year, and parallax = 18.78 mas (distance = 53 pc). However, until the advent of the Tycho2 catalog (Hog et. al. 2000), it was thought to be a single star. Analysis of proper motions in the Tycho2 catalog has revealed that the star TYC 03144-00630-1, V=10.56, B-V=0.99, has almost identical proper motions-differing by 2.3 mas/year, or 1 sigma, in the ra component, and minimally different in the declination component. The colors of the secondary suggest that it is a dwarf of spectral type late G or early K at a distance of 58+/-13 pc, consistent with the primary's distance.
The separation of 66.8 arcseconds, at the distance of the primary, corresponds to a projected orbital separation of 3560 AU, and a minimum period of 53,000 years. Assuming a total mass of 2 solar masses and favorable orientation, the orbital motion could conceivably account for the observed difference in proper motion.
The author(s) of this abstract have provided an email address for comments about the abstract: hindsley@nrl.navy.mil
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.