1 Introduction

The interplay of convection and rapid rotation results in chromospheric activity in late-type stars. For such stars rapid rotation occurs as the result of youth, before a stellar wind slows its rotation, or duplicity, where tidal forces cause the rotation of the stars to become synchronized. The "Catalog of Chromospherically Active Binary Stars (second edition)'' (CABS catalog; Strassmeier et al. 1993) lists basic information, including orbital elements and fundamental parameters, for over 200 active binaries.

Evidence of the dynamo, which is believed to be generated by the interaction of magnetic fields and rotation, includes CaII H and K emission lines and starspots. Some chromospherically active binaries are rotating so rapidly that the distribution of starspots can be mapped on their surfaces with the Doppler imaging technique (Vogt & Penrod 1983). In the course of such a project being carried out by the research group at the University of Vienna (e.g. Strassmeier & Rice 1998), a number of chromospherically active binaries have been observed spectroscopically for several seasons. To produce an accurate spot map the data must be correctly phased, so orbital elements should be carefully determined or updated. Thanks to back-to-back observing runs, arranged at the Kitt Peak National Observatory (KPNO) by the telescope-allocation committee, it was learned that additional spectra of many of the stars have been obtained by one of us (FCF), and so it was decided to combine our data.

In this paper we determine initial orbital elements for three binaries and update the elements of seven others. In the process we have found evidence of a tertiary component in two of the systems. The availability of the Hipparcos-parallax data base has enabled us to determine improved fundamental properties for the 10 systems.