Fundamental Properties of very low mass star and brown dwarf binaries

This work presents the results of a detailed study of the
statistical and physical properties of binary ultracool dwarfs and
brown dwarfs (spectral type later than M7). As for the statistical
properties, we found that the frequency of binaries among ultracool
objects is significantly lower than for earlier type objects, with
a lower limit at 10--15% in the field, and