Brown dwarfs are important objects because they may provide a missing link between stars and planets , two populations that have dramatically different formation history .
In this paper , we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during 2004 – 2011 observation seasons .
Based on the low mass ratio criterion of q < 0.2 , we found 7 candidate events , including OGLE-2004-BLG-035 , OGLE-2004-BLG-039 , OGLE-2007-BLG-006 , OGLE-2007-BLG-399/MOA-2007-BLG-334 , MOA-2011-BLG-104/OGLE-2011-BLG-0172 , MOA-2011-BLG-149 , and MOA-201-BLG-278/OGLE-2011-BLG-012N .
Among them , we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax .
The measured mass of the brown dwarf companions are ( 0.02 \pm 0.01 ) M _ { \odot } and ( 0.019 \pm 0.002 ) M _ { \odot } for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 , respectively , and both companions are orbiting low mass M dwarf host stars .
More microlensing brown dwarfs are expected to be detected as the number of lensing events with well covered light curves increases with new generation searches .