The Incidence of Multiplicity Among Bright Stellar Systems

We attempt to identify the multiplicities of the 4555 stellar systems that are brighter than Hipparcos magnitude 6.00. For multiplicity from one to seven, we find the following frequencies: 2723, 1411, 299, 86, 22, 12 and 2. That the higher multiplicities are significantly under-represented (except for multiplicity 7!) is illustrated by the fact that if we consider the smaller sample brighter than Hipparcos magnitude 4.00, we obtain: 213, 176, 52, 18, 9, 6, 0. We then construct a Monte-Carlo procedure that creates a population of multiples with multiplicity less than or equal to 8, giving them a plausible distribution over distance. In addition, we programme a `virtual observatory' that determines what observed multiplicities to expect from a given theoretical selection, subject to certain rather simple observational constraints. A crude first estimate is that to obtain something like the distribution listed above (for Hipparcos magnitude 6.00) we need a theoretical sample with about twice as many triples, and five times as many sextuples. We consider a number of evolutionary scenarios involving triples etc, including mergers that may mean that a system now perceived as binary may have formerly been triple.