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 mainly probeorbital 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 that the peak of the separation distribution ofbrown dwarf binaries lies right in the unprobed range. This work extendshigh-precision radial velocity surveys of brown dwarfs for the first time outto 3 AU. Based on more than six years UVES/VLT spectroscopy the binaryfrequency of brown dwarfs and (very) low-mass stars (M4.25-M8) in ChaI wasdetermined: 18% for the whole sample and 10% for the subsample of ten browndwarfs and VLMS (M < 0.1 Msun). Two spectroscopic binaries were confirmed, thebrown dwarf candidate ChaHa8 (previously discovered by Joergens & Mueller) andthe low-mass star CHXR74. Since their orbital separations appear to be 1 AU orgreater, the binary frequency at < 1 AU might be less than 10%. Now for thefirst time companion searches of (young) brown dwarfs cover the whole orbitalseparation range, and the following observational constraints for models ofbrown dwarf formation can be derived: (i) the frequency of brown dwarf and verylow-mass stellar binaries at < 3 AU does not significantly exceed that at > 3AU; i.e. direct imaging surveys do not miss a significant fraction of browndwarf binaries; (ii) the overall binary frequency of brown dwarfs and verylow-mass stars is 10-30 %; (iii) the decline in the separation distribution ofbrown dwarfs towards smaller separations seems to occur between 1 and 3 AU;(iv) the observed continuous decrease in the binary frequency from the stellarto the substellar regime is confirmed at < 3 AU providing further evidence of acontinuous formation mechanism from low-mass stars to brown dwarfs.

Binary frequency of very young brown dwarfs at separations smaller than 3 AU