Contact Binaries with Additional Components. I. The Extant Data

We have attempted to establish an observational evidence for presence ofdistant companions which may have acquired and/or absorbed the angular momentumduring evolution of multiple systems thus facilitating or enabling formation ofcontact binaries. In this preliminary investigation we use several techniques(some of them distance-independent) and mostly disregard detection biases ofindividual techniques in an attempt to establish a lower limit to the frequencyof triple systems. While the whole sample of 151 contact binary stars brighterthan Vmax = 10 mag. gives a firm lower limit of 42+/-5%, the correspondingnumber for the much better observed Northern-sky sub-sample is 59+/-8%. Theseestimates indicate that most contact binary stars exist in multiple systems.Comment: Accepted for publication in AJ (Feb.25, 2006). 10 figure