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A brown dwarf orbiting an M-dwarf : MOA 2009–BLG–411L
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(2012) A brown dwarf orbiting an M-dwarf : MOA 2009–BLG–411L. Astronomy & Astrophysics, Vol.547 . A55. doi:10.1051/0004-6361/201219765 Research output not available from this repository, contact author.
Official URL: http://dx.doi.org/10.1051/0004-6361/201219765
Abstract
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 M S = 0.05 M · orbiting a primary M-star of mass M P = 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. © 2012 ESO.
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Divisions: | Faculty of Science > Physics | ||||
| Journal or Publication Title: | Astronomy & Astrophysics | ||||
| Publisher: | EDP Sciences | ||||
| ISSN: | 0004-6361 | ||||
| Official Date: | 2012 | ||||
| Dates: |
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| Volume: | Vol.547 | ||||
| Page Range: | A55 | ||||
| DOI: | 10.1051/0004-6361/201219765 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access |
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