The formation of brown dwarfs as ejected stellar embryos

We conjecture that brown dwarfs are substellar objects because they have be en ejected from small newborn multiple systems that have decayed in dynamic al interactions. In this view, brown dwarfs are stellar embryos for which t he star formation process was aborted before the hydrostatic cores could bu ild up enough mass to eventually start hydrogen burning. The disintegration of a small multiple system is a stochastic process, which can be described only in terms of the half-life of the decay. A stellar embryo competes wit h its siblings in order to accrete infalling matter, and the one that grows slowest is most likely to be ejected. With better luck, a brown dwarf woul d therefore have become a normal star. This interpretation of brown dwarfs readily explains the rarity of brown dwarfs as close companions to normal s tars, the absence of wide brown dwarf binaries, and the flattening of the l ow-mass end of the initial mass function. Possible observational tests of t his scenario include statistics of brown dwarfs near Class 0 sources and th e kinematics of brown dwarfs in star-forming regions, while they still reta in a kinematic signature of their expulsion. Because the ejection process l imits the amount of gas brought along in a disk, it is predicted that subst ellar equivalents to the classical T Tauri stars should be rather short-liv ed.