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Published December 1, 2012 | Published
Journal Article Open

Microlensing Binaries with Candidate Brown Dwarf Companions

Abstract

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.

Additional Information

© 2012 American Astronomical Society. Received 2012 August 11; accepted 2012 October 3; published 2012 November 14. Work by C.H. was supported by the Creative Research Initiative Program (2009-0081561) of the National Research Foundation of Korea. The OGLE project has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 246678. The MOA experiment was supported by grants JSPS22403003 and JSPS23340064. T.S. was supported by the grant JSPS23340044. Y. Muraki acknowledges support from JSPS grants JSPS23540339 and JSPS19340058. The MiNDSTEp monitoring campaign is powered by ARTEMiS (Automated Terrestrial Exoplanet Microlensing Search; Dominik et al. 2008). M.H. acknowledges support by the German Research Foundation (DFG). D.R. (boursier FRIA), F.F. (boursier ARC), and J. Surdej acknowledge support from the Communauté française de Belgique Actions de recherche concertées – Académie universitaire Wallonie-Europe. K.A., D.M.B., M.D., K.H., M.H., C.L., C.S., R.A.S., and Y.T. are grateful to Qatar National Research Fund (QNRF), member of Qatar Foundation, for support by grant NPRP 09-476-1- 078. C.S. received funding from the European Union Seventh Framework Programme (FPT/2007–2013) under grant agreement no. 268421. This work is based in part on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La Silla Observatory. The Danish 1.54 m telescope is operated based on a grant from the Danish Natural Science Foundation (FNU). A. Gould and B. S. Gaudi acknowledge support from NSF AST-1103471. B. S. Gaudi, A. Gould, and R. W. Pogge acknowledge support from NASA grant NNG04GL51G. Work by J. C. Yee is supported by a National Science Foundation Graduate Research Fellowship under grant no. 2009068160. S. Dong's research was performed under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program. Research by T.C.H. was carried out under the KRCF Young Scientist Research Fellowship Program. T.C.H. and C.U.L. acknowledge the support of Korea Astronomy and Space Science Institute (KASI) grant 2012-1-410-02. I.A.B. and P.C.M.Y. acknowledge the support by the Marsden Fund of New Zealand.

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August 22, 2023
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