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Frank Grundahl

A brown dwarf orbiting an M-dwarf: MOA 2009-BLG-411L

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

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  • I.A. Bond, Microlensing Observations in Astrophysics
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  • J. Janczak, Ohio State University
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  • R.W. Pogge, Ohio State University
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  • K.R. Pollard, Department of Physics and Astronomy
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  • J.B. Hearnshaw, Department of Physics and Astronomy
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  • S. Brillant, European Southern Observatory (ESO)
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  • D.M. Bramich, European Southern Observatory
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  • E. Bertin, Université Pierre and Marie Curie
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  • V. Batista, Université Pierre and Marie Curie
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  • C. Coutures, Université Pierre and Marie Curie
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  • S. Dieters, Université Pierre and Marie Curie
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  • J.-B. Marquette, Université Pierre and Marie Curie
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  • C. Liebig, Zentrum für Astronomie der Universität Heidelberg (ZAH)
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  • G. Maier, Zentrum für Astronomie der Universität Heidelberg (ZAH)
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  • F. Zimmer, Zentrum für Astronomie der Universität Heidelberg (ZAH)
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  • P. Browne, University of St Andrews
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  • J.A.R. Caldwell, McDonald Observatory
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  • K.H. Cook, Lawrence Livermore National Laboratory
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  • D. Dominis Prester, University of Rijeka
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  • J. Donatowicz, Dept. of Computing
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  • A. Cole, University of Tasmania
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  • J. Greenhill, University of Tasmania
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  • S.R. Kane, Caltech, MS 100-22
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  • R. Martin, Perth Observatory
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  • A. Williams, Perth Observatory
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  • K.C. Sahu, Space Telescope Science Institute
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  • D. Graff, Korea Astronomy and Space Science Institute
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  • L.A.G. Monard, Bronberg Observatory
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  • P.J. Tristram, University of Cambridge
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  • C.H. Ling, North Shore Mail Centre
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  • F. Abe, Osaka University
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  • K. Furusawa, Osaka University
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  • Y. Itow, Osaka University
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  • K. Masuda, Osaka University
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  • Y. Matsubara, Osaka University
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  • N. Miyake, Osaka University
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  • T. Sumi, Osaka University
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  • D. Suzuki, Osaka University
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  • K. Wada, Osaka University
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  • E. Kerins, University of Manchester
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  • Y. Muraki, Konan University
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  • K. Ohnishi, Nagano National College of Technology
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  • C.S. Botzler, University of Auckland
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  • T. Saito, Tokyo Metropolitan College of Industrial Technology
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  • A.V. Korpela, Mount John Observatory
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  • D. Sullivan, Mount John Observatory
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  • E. Hawkins, Las Cumbres Observatory
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  • T.A. Lister, Las Cumbres Observatory
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  • E.S. Saunders, Las Cumbres Observatory
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  • M.F. Bode, Twelve Quays House
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  • N. Clay, Twelve Quays House
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  • S.N. Fraser, Twelve Quays House
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  • C.J. Mottram, Twelve Quays House
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  • I.A. Steele, Twelve Quays House
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  • A. Allan, University of Exeter
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  • P.J. Wheatley, University of Warwick
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  • K. Harpsøe, University of Copenhagen
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  • T.C. Hinse, University of Copenhagen
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  • J. Skottfelt, University of Copenhagen
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  • L. Mancini, Max Planck Institute for Astronomy
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  • D. Heyrovský, Charles University
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  • V. Bozza, INFN
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  • S. Calchi Novati, INFN
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  • G. Scarpetta, INFN
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  • S. Rahvar, Sharif University of Technology
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  • S. Dreizler, Georg-August Universität
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  • F.V. Hessman, Georg-August Universität
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  • M. Hundertmark, Georg-August Universität
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  • F. Finet, Institut d'Astrophysique et de Géophysique
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  • D. Ricci, Institut d'Astrophysique et de Géophysique
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  • J. Surdej, Institut d'Astrophysique et de Géophysique
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  • J. Southworth, Keele University
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  • J. Drummond, Wendelstein Calar Alto Pixellensing Project
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  • S. Kaspi, Tel-Aviv University
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  • D. Polishook, Tel-Aviv University
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  • A. Shporer, Tel-Aviv University
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  • N. Matsunaga, University of Tokyo
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  • N. Oi, Graduate University for Advanced Studies (Sokendai)
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  • N. Renon, Université de Toulouse
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  • C.-U. Lee, Korea Astronomy and Space Science Institute
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  • B.-G. Park, Korea Astronomy and Space Science Institute
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  • M. Glitrup, Denmark
  • F. Grundahl
  • M. Bos, Molehill Astronomical Observatory
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  • J.A. Muñoz, Universidad de Valencia
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  • S. Dong, Institute for Advanced Study
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  • A. Fukui, National Astronomical Observatory of Japan
Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the companion signal to be extracted. Aims. MOA 2009-BLG-411 was detected on August 5, 2009 by the MOA-Collaboration. Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. Methods. Thanks to observations by all the collaborations, this event was well monitored. We first decided to characterize the source star properties by using a more refined method than the classical one: we measure the interstellar absorption along the line of sight in five different passbands (VIJHK). Secondly, we model the lightcurve by using the standard technique: make (s,q,α) grids to look for local minima and refine the results by using a downhill method (Markov chain Monte Carlo). Finally, we use a Galactic model to estimate the physical properties of the lens components. Results. We find that the source star is a giant G star with radius 9 R . The grid search gives two local minima, which correspond to the theoretical degeneracy s s . We find that the lens is composed of a brown dwarf secondary of mass M = 0.05 M orbiting a primary M-star of mass M = 0.18 M . We also reveal a new mass-ratio degeneracy for the central caustics of close binaries. Conclusions. As far as we are aware, this is the first detection using the microlensing technique of a binary system in our Galaxy composed of an M-star and a brown dwarf.
Original languageEnglish
JournalAstronomy & Astrophysics
Volume547
IssueNovember
Pages (from-to)A55
Number of pages12
ISSN0004-6361
DOIs
Publication statusPublished - 2012

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