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Authors: Pribulla, T., Rucinski, S.M.
Title:  "Contact binaries as members of multiple systems"


We have attempted to establish an observational evidence for the
presence of distant companions to contact binaries which may have
stored the angular momentum excess at the early stages of evolution.
Since none of the techniques used to detect companions
can provide the true frequency, but only a lower limit to it,
we utilized several observational techniques and
attempted to collect diversified evidences
to establish a firm lower limit to the frequency of
triple stars with one component being a contact binary. While
whole sample of 138 contact binary stars brighter than V = 10mag
shows 38+-5% incidence, the sub-sample of the northern contact
binaries gives the frequency of 51+-8%. This number is
higher than previously thought, supporting the hypothesis that
all close binary stars are formed within multiple systems.