Multiplicity of contact binary stars

We present results of a preliminary investigation of triple star incidence for contact binary stars. The goal is to shed light on the possible role of distant companions which may have acquired and/or absorbed AM during evolution of multiple systems facilitating or enabling formation of contact binaries. We used several techniques but mostly disregarded their detection biases in an attempt to establish a low limit to the frequency of triple systems. The result for the much better observed Northern-sky subsample is 56% +/-8%, whereas subsamples of systems best observed using individual techniques indicate apparent frequencies as high as 60% to 67%; this is consistent with the hypothesis that all contact binary stars exist in multiple systems.