We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
A brown dwarf orbiting an M-dwarf: MOA 2009-BLG-411L.
- Authors
Bachelet, E.; Fouqué, P.; Han, C.; Gould, A.; Albrow, M. D.; Beaulieu, J.-P.; Bertin, E.; Bond, I. A.; Christie, G. W.; Heyrovský, D.; Horne, K.; Jørgensen, U. G.; Maoz, D.; Mathiasen, M.; Matsunaga, N.; McCormick, J.; Menzies, J.; Nataf, D.; Natusch, T.; Oi, N.
- 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 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
- Subjects
DWARF stars; CAUSTICS (Optics); GIANT stars; INTERSTELLAR medium; ASTRONOMY; ASTROPHYSICS
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2012, Vol 547, p1
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/201219765