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SUMMARY:Spectral Binaries: An Approach for Measuring the True Binary Fract
 ion of Very Low Mass Stars and Brown Dwarfs  - Adam Burgasser (UC San Dieg
 o)
DTSTART:20160427T143000Z
DTEND:20160427T151500Z
UID:TALK65941@talks.cam.ac.uk
CONTACT:Dr B.-O. Demory
DESCRIPTION:The multiplicative properties of stars and brown dwarfs are fu
 ndamentally tied to their formation mechanisms\, while multiple systems pr
 ovide opportunities for direct mass measurements and tests of evolutionary
  theories and atmosphere models. The prevailing wisdom in the community is
  that the binary fraction of stars declines with mass\, reaching 10-20% in
  the very-low-mass (VLM: M < 0.1 solar masses) regime.  However\, results 
 for VLM dwarfs are based almost entirely on resolved imaging programs\, wh
 ich are limited in both projected separation and detectable mass ratios\; 
 alternate approaches suggest VLM binary fractions up to 3x higher. Capital
 izing on the distinct spectral morphologies of late-M\, L and T dwarfs\, w
 e have developed a robust approach for identifying VLM spectral binaries\,
  systems identified by their blended-light spectra. Over 50 spectral binar
 y candidates have been identified to date\, and over a dozen systems confi
 rmed through a combination of high resolution imaging\, radial velocity mo
 nitoring and astrometric monitoring\, including some of the shortest-perio
 d VLM binaries currently known. In this talk\, I discuss our spectral bina
 ry methodology\; review our follow-up program\; and describe several of ou
 r key discoveries\, including systems straddling the hydrogen burning mass
  limit with full orbit determinations. Examining the currently confirmed s
 ample\, I then critically analyze the VLM separation distribution and over
 all binary fraction\, and discuss its possible impact on current star and 
 brown dwarf formation models.
LOCATION:Sackler Lecture Theatre\, IoA
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