MSC - A CATALOG OF PHYSICAL MULTIPLE STARS

The MSC catalogue contains data on 612 physical multiple stars of mult iplicity 3 to 7 which are hierarchical with few exceptions. Orbital pe riods, angular separations and mass ratios are estimated for each subs ystem. Orbital elements are given when available. The catalogue can be accessed through CDS (Strasbourg). Half of the systems are within 100 pc from the Sun. The comparison of the periods of close and wide sub- systems reveals that there is no preferred period ratio and all possib le combinations of periods are found. The distribution of the logarith ms of short periods is bimodal, probably due to observational selectio n. In 82% of triple stars the close subsystem is related to the primar y of a wide pair. However, the analysis of mass ratio distribution giv es some support to the idea that component masses are independently se lected from the Salpeter mass function. Orbits of wide and close sub-s ystems are not always coplanar, although the corresponding orbital ang ular momentum vectors do show a weak tendency of alignment. Some obser vational programs based on the MSC are suggested.