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C.H. Lineweaver (Australian National University), D. Grether (University of New South Wales)
The formation of a binary star via molecular cloud collapse and fragmentation, and the formation of a massive planet around a host star via protoplanetary disk accretion, both involve the production of a binary system, but are recognized as distinct processes. The formation of companion brown dwarfs with masses in between the stellar and planetary mass ranges may have elements of both, or some more distinct mechanism. To constrain and differentiate models of the formation of these companions, we analyse the close companions (P < 5 years) of nearby Sun-like stars (d < 25 pc & d < 50 pc). By using the same sample to extract the relative numbers of stellar, brown dwarf and planetary companions, we are able to verify the existence of the brown dwarf desert and decribe it quantitatively. The mass function drops by more than an order of magnitude from solar mass companions to the brown dwarf mass range and rises by approximately half an order of magnitude as we move from brown dwarfs to Jupiter mass objects. The companion mass function in the brown dwarf and stellar mass range, has a different shape than the mass function of single stars and free-floating brown dwarfs. We discuss the possible origins of this difference in terms of formation mechanisms or post-formation migratory processes.
The author(s) of this abstract have provided an email address for comments about the abstract: charley@bat.phys.unsw.edu.au
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.