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1 National Space Institute, Technical University of Denmark2 Astrophysics, National Space Institute, Technical University of Denmark3 IT-Department, National Space Institute, Technical University of Denmark4 Chungbuk National University5 Ohio State University6 University of Warsaw7 Osaka University8 University of St. Andrews9 Université Pierre et Marie Curie10 Las Cumbres Observatory Global Telescope Network11 Università degli Studi di Salerno12 Nagoya University13 University of Notre Dame14 Massey University15 University of Auckland16 University of Canterbury17 Mt John Observatory18 Victoria University of Wellington19 Konan University20 Nagano National College of Technology21 Tokyo Metropolitan College of Industrial Technology22 Auckland Observatory23 Texas A&M University24 Institute for Advanced Study25 Weizmann Institute of Science26 University of California, Los Angeles27 Tel Aviv University28 Farm Cove Observatory29 Kumeu Observatory30 Universidad de Valencia31 University of Arizona32 Perth Exoplanet Survey Telescope33 Korea Astronomy and Space Science Institute34 European Southern Observatory35 Qatar Foundation36 Max Planck Institute37 Liverpool John Moores University38 HE Space Operations GmbH39 University of Göttingen40 Chinese Academy of Sciences41 Aarhus University42 University of Copenhagen43 University of Manchester44 University of Heidelberg45 Sharif University of Technology46 Institut d'Astrophysique et de Géophysique47 Keele University48 McDonald Observatory49 University of The Free State50 University of Tasmania51 Lawrence Livermore National Laboratory52 University of Rijeka53 Vienna University of Technology54 Université de Toulouse55 California Institute of Technology56 Perth Observatory57 South African Astronomical Observatory58 Space Telescope Science Institute59 Chungbuk National University60 University of Warsaw61 Osaka University62 University of St. Andrews63 Nagoya University64 University of Notre Dame65 Massey University66 Victoria University of Wellington67 Konan University68 Weizmann Institute of Science69 Tel Aviv University70 University of Arizona71 Korea Astronomy and Space Science Institute72 European Southern Observatory73 Liverpool John Moores University74 University of Heidelberg75 Sharif University of Technology76 Keele University77 University of The Free State78 Lawrence Livermore National Laboratory79 University of Rijeka80 California Institute of Technology81 South African Astronomical Observatory82 Space Telescope Science Institute
Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during the 2004-2011 observation seasons. Based on the low mass ratio criterion of q <0.2, we found seven candidate events: 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 masses of the brown dwarf companions are 0.02 ± 0.01 M⊙ and 0.019 ± 0.002 M⊙ 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.
Astrophysical Journal, 2012, Vol 760:116, Issue 2, p. 1-10