Issue |
A&A
Volume 547, November 2012
|
|
---|---|---|
Article Number | A55 | |
Number of page(s) | 12 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/201219765 | |
Published online | 25 October 2012 |
A brown dwarf orbiting an M-dwarf: MOA 2009–BLG–411L⋆
1
Probing Lensing Anomalies Network, http://planet.iap.fr
2
Microlensing Follow Up Network, http://www.astronomy.ohio-state.edu/~microfun
3
The Optical Gravitational Lensing Experiment, http://ogle.astrouw.edu.pl
4
Microlensing Observations in Astrophysics, http://www.phys.canterbury.ac.nz/moa
5
Robotic Telescope Network, http://robonet.lcogt.net
6
Microlensing Network for the Detection of Small Terrestrial Exoplanets,
http://www.mindstep-science.org
7
Department of Astronomy, Ohio State University,
140 West 18th Avenue,
Columbus, OH
43210,
USA
8
University of Canterbury, Department of Physics &
Astronomy, Private Bag
4800, Christchurch
8020, New
Zealand
9
European Southern Observatory (ESO), Casilla 19001, Vitacura 19, Santiago, Chile
10
European Southern Observatory, Karl-Schwarzschild-Stra β 2,
85748
Garching bei München,
Germany
11
Institut d’Astrophysique de Paris, CNRS, Université Pierre
& Marie Curie, 98bis Bd
Arago, 75014
Paris,
France
12
Astronomisches Rechen-Institut (ARI), Zentrum für Astronomie der
Universität Heidelberg (ZAH), Mönchhofstrasse 12ŋ-14, 69120
Heidelberg,
Germany
13
Scottish Universities Physics Alliance, School of Physics
& Astronomy, University of St Andrews, North Haugh, St Andrews, KY16
9SS, UK
14
University of Notre Dame, Department of Physics,
225 Nieuwland Science Hall,
Notre Dame, IN
46556,
USA
15
University of Texas, McDonald Observatory,
16120 St Hwy Spur 78,
Fort Davis
TX
79734,
USA
16
Institute of Geophysics and Planetary Physics (IGPP), L-413,
Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA
94551,
USA
17
Physics Department, Faculty of Arts and Sciences, University of
Rijeka, Omladinska
14, 51000
Rijeka,
Croatia
18
Technical University of Vienna, Dept. of Computing, Wiedner Hauptstrasse 10,
Vienna,
Austria
19
School of Mathematics and Physics, University of
Tasmania, Private Bag 37,
Hobart, 7001
Tasmania,
Australia
20
NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue,
Pasadena, CA
91125,
USA
21
Perth Observatory, Walnut Road, Bickley, Perth
6076,
Australia
22
South African Astronomical Observatory,
PO Box 9, 7925
Observatory, South
Africa
23
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD
21218,
USA
24
Department of Physics, Institute for Basic Science Research,
Chungbuk National University, 361-763
Chongju,
Korea
25
Korea Astronomy and Space Science Institute,
61-1, Whaam-Dong, Youseong-Gu,
305-348
Daejeon,
Korea
26
Bronberg Observatory, Pretoria, South
Africa
27
Warsaw University Observatory. Al. Ujazdowskie 4,
00-478
Warszawa,
Poland
28
Universidad de Concepción, Departamento de Física, Astronomy Group,
Casilla 160-C,
Concepción,
Chile
29
Institute of Astronomy, University of Cambridge,
Madingley Road, Cambridge
CB3 0HA,
UK
30
Institute of Information and Mathematical Sciences, Massey
University, Private Bag 102-904,
North Shore Mail Centre, Auckland, New Zealand
31
Department of Earth and Space Science, Osaka
University, 560-0043
Osaka,
Japan
32
Jodrell Bank Centre for Astrophysics, University of
Manchester, Manchester
M13 9PL,
UK
33
Department of Physics, Konan University,
Nishiokamoto 8-9-1,
658-8501
Kobe,
Japan
34
Nagano National College of Technology,
381-8550
Nagano,
Japan
35
Department of Physics, University of Auckland,
Private Bag 92019, 1142
Auckland, New
Zealand
36
Tokyo Metropolitan College of Industrial Technology,
116-0003
Tokyo,
Japan
37
Department of Physics and Astrophysics, Faculty of Science, Nagoya
University, 464-8602
Nagoya,
Japan
38
Mount John Observatory, PO Box 56, 8770
Lake Tekapo, New
Zealand
39
Las Cumbres Observatory, 6740B Cortona Dr, suite 102, Goleta, CA
93117,
USA
40
Astrophysics Research Institute, Liverpool John Moores
University, Twelve Quays House,
Egerton Wharf, Birkenhead
CH41 1LD,
UK
41
School of Physics, University of Exeter,
Stocker Road, Exeter
EX4 4QL,
UK
42
Department of Physics, University of
Warwick, Coventry,
CV4 7AL,
UK
43
Department of Physics, Broida Hall, University of
California, Santa
Barbara
CA
93106-9530,
USA
44
IRAP, Université de Toulouse, CNRS, 14 avenue Edouard Belin, 31400
Toulouse,
France
45
Niels Bohr Institute and Centre for Star and Planet Formation,
University of Copenhagen, Juliane
Maries Vej 30, 2100
Copenhagen,
Denmark
46
University Observatory Munich, Scheinerstrasse 1, 81679
München,
Germany
47
Max Planck Institute for Astronomy, Königstuhl 17, 69117- Heidelberg, Germany
48
Institute of Theoretical Physics, Charles
University, V Holešovičkách
2, 18000
Prague, Czech
Republic
49
Bellatrix Observatory, via Madonna de Loco 47, 03023
Ceccano,
Italy
50
Dipartimento di Fisica, Università di Salerno, Fisciano, INFN,
sez. di Napoli,
IIASS, Vietri sul
Mare, Italy
51
Armagh Observatory, College Hill, Armagh, BT61
9DG, UK
52
Department of Physics, Sharif University of
Technology, PO Box
11155-9161, Tehran,
Iran
53
Institut für Astrophysik, Georg-August Universität,
Friedrich-Hund-Platz 1,
37077
Göttingen,
Germany
54
Institut d’Astrophysique et de Géophysique,
Allée du 6 Août, Sart Tilman, Bât.
B5c, 4000
Liège,
Belgium
55
Astrophysics Group, Keele University, Newcastle-under-Lyme, ST5 5BG, UK
56
INAF, Osservatorio Astronomico di Brera,
23846
Merate ( LC), Italy
57
Deutsches SOFIA Institut, Universität Stuttgart,
Pfaffenwaldring 31,
70569
Stuttgart,
Germany
58
SOFIA Science Center, NASA Ames Research Center, Mail Stop
N211-3, Moffett Field
CA
94035,
USA
59
Department of Astronomy, Kyoto University,
606-8502
Kyoto,
Japan
60
School of Mathematical Sciences, Queen Mary University of
London, Mile End
Road, London
E1 4NS,
UK
61 The Wendelstein Calar Alto Pixellensing Project, http://www.usm.uni-muenchen.de/people/arri/wecapp.html
62
Possum Observatory, Patutahi, Gisbourne, New Zealand
e-mail: john_drummond@xtra.co.nz
63
School of Physics and Astronomy and Wise Observatory, Tel-Aviv
University, Tel-Aviv
69978,
Israel
e-mail: shai@wise.tau.ac.il; dani@wise.tau.ac.il; shporer@wise.tau.ac.il; david@wise.tau.ac.il
64
Auckland Observatory, Auckland, New
Zealand
e-mail: gwchristie@christie.org.nz
65
Farm Cove Observatory, Centre for Backyard
Astrophysics, Pakuranga, Auckland, New Zealand
e-mail: farmcoveobs@xtra.co.nz
66
Kiso Observatory, Institute of Astronomy, The University of
Tokyo, 10762-30, Mitake,
Kiso, 397-0101
Nagano,
Japan
67
Teide Observatory
68
The Graduate University for Advanced Studies
(Sokendai), 2-21-1 Oosawa,
Mitaka, 181-8588
Tokyo,
Japan
69
CALMIP, DTSI Université Paul Sabatier, Université de
Toulouse, 31062
Toulouse,
France
70
Perimeter Institute for Theoretical Physics,
31 Caroline Street North,
Waterloo, ON
N2L 2Y5,
Canada
71
Korea Astronomy and Space Science Institute, 776
Daedukdae-ro, Yuseong-gu, 305-348 Daejeon, Republic of Korea (South Korea)
72
International Institute for Advanced Scientific Studies, via G. Pellegrino 19,
84019 – Vietri sul Mare ( SA), Italy
73
Department of Physics, University of Salerno, via Ponte Don Melillo, 84084 –
Fisciano ( SA), Italy
74
Department of Physics & Astronomy, Aarhus
Universitet, Ny
Munkegade, 8000
Aarhus C,
Denmark
75
Molehill Astronomical Observatory, Auckland, New
Zealand
76
Departamento de Astronomía y Astrofísica, Universidad de
Valencia, 46100
Burjassot, Valencia, Spain
77
Dept. of Physics, Texas A&M University,
College Station, TX, USA
78
Institute for Advanced Study, Einstein Drive, Princeton, NJ
08540,
USA
79
AUT University, Auckland, New Zealand
80
Okayama Astrophysical Observatory, National Astronomical
Observatory of Japan, Asaguchi,
719-0232
Okayama,
Japan
Received: 6 June 2012
Accepted: 27 August 2012
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-1. We find that the lens is composed of a brown dwarf secondary of mass MS = 0.05 M⊙ orbiting a primary M-star of mass MP = 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.
Key words: binaries: general / gravitational lensing: micro / stars: individual: MOA 2009-BLG-411L
Appendix is available in electronic form at http://www.aanda.org
© ESO, 2012
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