English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Searches for companions of brown dwarfs by direct imaging probe mainlyorbital separations > 3-10 AU. On the other hand, previous radial velocitysurveys of brown dwarfs are mainly sensitive to separations smaller than 0.6AU. It has been speculated if the peak of the separation distribution of browndwarf binaries lies right in the unprobed range. Very recent work for the firsttime extends high-precision radial velocity surveys of brown dwarfs out to 3 AU(Joergens 2008, A&A). Based on more than six years UVES/VLT spectroscopy thebinary frequency of brown dwarfs and (very) low-mass stars (M4.25-M8) in ChaIwas determined: it is 18% for the whole sample and 10% for the subsample of tenbrown dwarfs and VLMS (M < 0.1 Msun). Two spectroscopic binaries wereconfirmed, these are the brown dwarf candidate ChaHa8, and the low-mass starCHXR74. Since their orbital separations appear to be 1 AU or greater, thebinary frequency at < 1 AU might be less than 10%. Now for the first timecompanion searches of (young) brown dwarfs cover the whole orbital separationrange and the following observational constraints for models of brown dwarfformation can be derived: (i) the frequency of brown dwarf and very low-massstellar binaries at < 3 AU is not significantly exceeding that at > 3 AU; i.e.direct imaging surveys do not miss a significant fraction of brown dwarfbinaries; (ii) the overall binary frequency of brown dwarfs and very low-massstars is 10-30 %; (iii) the decline of the separation distribution of browndwarfs towards smaller separations seem to occur between 1 and 3 AU; (iv) theobserved continuous decrease of the binary frequency from the stellar to thesubstellar regime is confirmed at < 3 AU providing further evidence for acontinuous formation mechanism from low-mass stars to brown dwarfs.

Where lies the peak of the brown dwarf binary separation distribution ?