2004/02/12 by M. R. Zapatero Osorio, E. L. Martı́n, E. L. Martin · 1 citation
Physics and Astronomy · #Adaptive optics and wavefront sensing #Angular momentum #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Metallicity #Orbital motion #Photometry (optics) #Physics #Proper motion #Sky #Stars #Stellar classification #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20035907
published as Astron.Astrophys. 419 (2004) 167-180 · Accepted for publication in A&A. (Table 1 is included)
arxiv created 2004/02/12 · openalex publication_date 2004/04/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We explored the regions within a radius of 25´´ around 473 nearby, low-metallicity G- to M-type stars using optical filters and small-aperture telescopes. About 10% of the sample was searched up to angular separations of 90´´. We applied photometric and astrometric techniques to detect true physical companions to the targets. The great majority of the sample stars was drawn from the Carney–Latham surveys; their metallicities range from roughly solar to [Fe/H] = -3.5 dex. Our I-band photometric survey detected objects that are between 0 and 5 mag fainter (completeness) than the target stars; the maximum dynamical range of our exploration is 9 mag. We also investigated the literature, and inspected images from the Digitized Sky Surveys to complete our search. By combining photometric and proper motion measurements, we retrieved 29 previously known companions, and identified 13 new proper motion companions. Near-infrared 2MASS photometry is provided for the great majority of them. Low-resolution optical spectroscopy (386–1000 nm) was obtained for eight of the new companion stars. These spectroscopic data confirm them as cool, late-type, metal-depleted dwarfs, with spectral classes from esdK7 to sdM3. After comparison with low-metallicity evolutionary models, we estimate the masses of the proper motion companion stars to be in the range 0.5–0.1 . They are moving around their primary stars at projected separations between ~32 and ~57 000 AU. These orbital sizes are very similar to those of solar-metallicity stars of the same spectral types. Our results indicate that about 15% of the metal-poor stars have stellar companions in wide orbits, which is in agreement with the binary fraction observed among main sequence G- to M-type stars and T Tauri stars.