Multiplicity of contact binaries

In this preliminary investigation we use several techniques (some of them distance- independent) and mostly disregard the detection biases of individual techniques in an attempt to establish a lower limit to the frequency of triple systems.

While the whole sample of 151 contact binary stars brighter than V_max_=10mag gives a firm lower limit of 42%{+/-}5%, the corresponding number for the much better observed northern-sky subsample is 59%{+/-}8%. These estimates indicate that most contact binary stars exist in multiple systems.