2001/09/06 by Rainer Koehler, Rainer Köhler · 34 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Hertzsprung–Russell diagram #K-type main-sequence star #Multiplicity (mathematics) #Population #Stars #Stellar, planetary, and galactic studies #T Tauri star #astro-ph
paper · pdf · doi:10.1086/323919
published in The Astronomical Journal 122(6), 3325-3334 (Institute of Physics) · 15 pages, 9 figures, to be published in The Astronomical Journal
arxiv created 2001/09/06 · openalex publication_date 2001/12/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report on a multiplicity survey of a sample of X-ray–selected young stars in the Chamaeleon association. We used speckle interferometry and direct imaging to find companions in the separation range 0 13–6''. After correction for chance alignment with background stars, we find a multiplicity (number of binaries or multiples divided by number of systems) of 14.0% ± 4.3% and a companion-star frequency (number of companions divided by number of systems) of 14.7% ± 5.1%. Compared with solar-type main-sequence stars, the companion-star frequency is lower by a factor of 0.61 ± 0.27. This is remarkably different from the high multiplicity found in the Taurus-Auriga star-forming region and for T Tauri stars in Chamaeleon known before ROSAT . We find only a few binaries with projected separations of more than 70 AU, also in contrast to the results for stars known before ROSAT . This indicates that the X-ray–selected stars belong to a different population than the stars known before ROSAT , a hypothesis further supported by their Hipparcos distances and proper motions.