2002/05/29 by Guillermo Torres, Torres, Guillermo, Andrew F. Boden +8
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #History and Developments in Astronomy #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0205511
52 pages (including 11 figures), to appear in The Astronomical Journal, September 2002
arxiv created 2002/05/29 · openalex publication_date 2002/05/29 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report spectroscopic and interferometric observations of the moderately\nmetal-poor double-lined binary system HD 195987, with an orbital period of 57.3\ndays. By combining our radial-velocity and visibility measurements we determine\nthe orbital elements and derive absolute masses for the components of M(A) =\n0.844 +/- 0.018 Msun and M(B) = 0.6650 +/- 0.0079 Msun, with relative errors of\n2% and 1%, respectively. We also determine the orbital parallax, pi(orb) =\n46.08 +/- 0.27 mas, corresponding to a distance of 21.70 +/- 0.13 pc. The\nparallax and the measured brightness difference between the stars in V, H, and\nK yield the component absolute magnitudes in those bands. We also estimate the\neffective temperatures of the stars as Teff(A) = 5200 +/- 100 K and Teff(B) =\n4200 +/- 200 K. Together with detailed chemical abundance analyses from the\nliterature giving [Fe/H] approximately -0.5 (corrected for binarity) and\n[alpha/Fe] = +0.36, we use these physical properties to test current models of\nstellar evolution for metal-poor stars. Among the four that we considered, we\nfind that no single model fits all observed properties at the measured\ncomposition, although we identify the assumptions in each one that account for\nthe discrepancy and we conclude that a model with the proper combination of\nassumptions should be able to reproduce all the radiative properties. The\nindications from the isochrone fits and the pattern of enhancement of the\nmetals in HD 195987 are consistent with this being a thick disk object, with an\nage of 10-12 Gyr.\n