brown dwarfs; gravitational lensing: micro; planetary systems; planets and satellites: formation; planets and satellites: general; techniques: photometric
Abstract :
[en] We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales >200 days. Its dereddened color, (V - I)[SUB] S, 0[/SUB], is 1.221 ± 0.051 mag, and from our lens model we derive a source radius of 14.7 ± 1.3 R [SUB]&sun;[/SUB], suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 ± 0.0006. The Einstein crossing time of the event, t [SUB]E[/SUB] = 44.3 ± 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, D[SUB]L[/SUB] = 2.8 ± 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with M [SUB] L, 1[/SUB] = 0.16 ± 0.03 M [SUB]&sun;[/SUB], while the companion has M [SUB] L, 2[/SUB] = 11.0 ± 2.0 M [SUB]J[/SUB], putting it in the boundary zone between planets and brown dwarfs.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Street, R. A.; LCOGT, 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USA
Choi, J.-Y.; Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 361-763, Republic of Korea
Tsapras, Y.; LCOGT, 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USA ; School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
Han, C.; Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 361-763, Republic of Korea ; Corresponding author.
Furusawa, K.; Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan
Hundertmark, M.; SUPA/St Andrews, Department of Physics and Astronomy, North Haugh, St. Andrews, Fife KY16 9SS, UK
Gould, A.; Department of Astronomy, Ohio State University, McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210-1173, USA
Sumi, T.; Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
Bond, I. A.; Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland, New Zealand
Wouters, D.; UPMC-CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98bis boulevard Arago, F-75014 Paris, France
Zellem, R.; Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721-0092, USA
DePoy, D. L.; Department of Physics and Astronomy, Texas A&M University College Station, TX 77843-4242, USA
Gaudi, B. S.; Department of Astronomy, Ohio State University, McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210-1173, USA
Hung, L.-W.; Department of Astronomy, Ohio State University, McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210-1173, USA
Jablonski, F.; Divisao de Astrofisica, Instituto Nacional de Pesquisas Espeaciais, Avenida dos Astronauntas, 1758 Sao José dos Campos, 12227-010 SP, Brazil
Kaspi, S.; School of Physics and Astronomy and Wise Observatory, Tel-Aviv University, Tel-Aviv 69978, Israel
Klein, N.; School of Physics and Astronomy and Wise Observatory, Tel-Aviv University, Tel-Aviv 69978, Israel
Hwang, K.-H.; Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 361-763, Republic of Korea
Koo, J.-R.; Korea Astronomy & Space Science Institute, Daejeon 305-348, Republic of Korea
Maoz, D.; School of Physics and Astronomy and Wise Observatory, Tel-Aviv University, Tel-Aviv 69978, Israel
Muñoz, J. A.; Departamento de Astronomiá y Astrofísica, Universidad de Valencia, E-46100 Burjassot, Valencia, Spain
Greenhill, J.; School of Math and Physics, University of Tasmania, Private Bag 37, GPO Hobart, Tasmania 7001, Australia
Pogge, R. W.; Department of Astronomy, Ohio State University, McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210-1173, USA
Polishhook, D.; School of Physics and Astronomy and Wise Observatory, Tel-Aviv University, Tel-Aviv 69978, Israel
Shporer, A.; LCOGT, 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USA ; Department of Physics and Astronomy, Texas A&M University College Station, TX 77843-4242, USA
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Corrales, E.; Institut d'Astrophysique de Paris, UMR7095 CNRS-Université Pierre & Marie Curie, 98 bis Boulevard Arago, F-75014 Paris, France
Coutures, Ch; Institut d'Astrophysique de Paris, UMR7095 CNRS-Université Pierre & Marie Curie, 98 bis Boulevard Arago, F-75014 Paris, France
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Bachelet, E.; Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, UPS-OMP, IRAP, BP 44346-31028 Toulouse cedex 04, Toulouse, France ; CNRS, IRAP, 14 Avenue Edouard Belin, F-31400 Toulouse, France
Marquette, J.-B.; Institut d'Astrophysique de Paris, UMR7095 CNRS-Université Pierre & Marie Curie, 98 bis Boulevard Arago, F-75014 Paris, France
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MiNDSTEp
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