2004/12/07 by S. Tsangarides, S. G. Ryan, T. C. Beers
Physics and Astronomy · #astro-ph
published as Mem.Soc.Ast.It. 75 (2004) 772 · 6 pages, 2 tables, 1 figure, Mem. S. A. It., in press
arxiv created 2004/12/07 · arxiv updated 2009/12/01
We report on a programme to monitor the radial velocities of a sample of candidate and confirmed carbon-enhanced, metal-poor (CEMP) stars. We observed 45 targets using the Echelle Spectrographs of three 4m class telescopes. Radial velocities for these objects were calculated by cross-correlation of their spectra with the spectrum of HD 140283, and have errors < 1 km/s. Sixteen of our programme's targets have reported carbon excess, and nine of these objects also exhibit s-process enhancements (CEMP-s). We combine these stars' radial velocities with other literature studies in search of binarity. The search reveals that four of our CEMP-s stars (44%) are in binary systems. Using the analysis of Lucatello et al. (2004), we find that all the CEMP-s stars in our sample are binaries. This conclusion implies that CEMP-s stars may be the very metal-poor relatives of CH and Ba II stars, which are believed to have acquired their peculiar abundance patterns by mass transfer from a thermally-pulsing AGB companion.