Orbital motion monitoring of A-star multiples

For each system with an estimated orbit, the dynamical system mass obtained was compared with the system mass estimated from mass-magnitude relations. Discrepancies between the dynamical and theoretical system mass can be explained by the presence of a previously unresolved spectroscopic component, or by a non-solar metallicity of the system.

Using this approach to infer the presence of additional companions, a lower limit to the fraction of binaries, triples, and quadruples can be estimated as 39%, 46%, and 15%, for systems with at least one companion within 100AU. The fraction of multiple systems with three or more components shows a relative increase compared to the fraction for Solar-type primaries resolved in previous volume-limited surveys. The observations have also revealed a pair of potentially young (<100Myr) M-dwarf companions, which would make an ideal benchmark for the theoretical models during the pre-Main Sequence contraction phase for M-dwarfs.