HD 109556

Spectroscopic characterization of a sample of southern visual binaries Aims.We present the spectroscopic characterization of 56 pairs of visualbinaries with similar components, based on high resolution spectraacquired with FEROS at ESO La Silla. Methods: .For all stars, wemeasured radial and rotational velocities and CaII H&K emission. Results: .Five previously unknown double lined spectroscopic binarieswere found. Six other pairs show velocity differences that are notcompatible with the orbital motion of the wide pair, indicating thepresence of further companion(s) in the system. The fraction of visualbinaries that contain additional spectroscopic components is27±10%, compatible with other literature estimates. The ages ofthe components of the pairs derived from chromospheric activitytypically show apparent differences of about 0.2 dex. A few pairs show arather large difference in activity level, but in most cases this isconsistent with the variability of chromospheric emission observed forthe Sun along its magnetic cycle.
UVBY Bet study of A-and F-type visual binaries. II. Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978AJ.....83.1646M&db_key=AST
A list of stars with common proper motions. Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958AJ.....63..246V&db_key=AST

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