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

Bachelet, E; Fouque, P; Han, C; Gould, A; Albrow, MD; Beaulieu, J-P; Bertin, E; Bond, IA; Christie, GW; Heyrovski, D; Horne, K; Jorgensen, UG; Maoz, D; Mathiasen, M; Matsunaga, N; McCormick, J; Menzies, J; Nataf, D; Natusch, T; Oi, N; Renon, N; Tsapras, Y; Udalski, A; Yee, JC; Batista, V; Bennett, DP; Brillant, S; Caldwell, JAR; Cassan, A; Cole, A; Cook, KH; Coutures, C; Dieters, S; Dominik, M; Dominis Prester, D; Donatowicz, J; Greenhill, J; Kains, N; Kane, SR; Marquette, J-B; Martin, R; Pollard, KR; Sahu, KC; Street, RA; Wambsganss, J; Williams, A; Zub, M; Bos, M; Dong, S; Drummond, J; Gaudi, BS; Graff, D; Janczak, J; Kaspi, S; Kozlowski, S; Lee, C-U; Monard, LAG; Munoz, JA; Park, B-G; Pogge, RW; Polishook, D; Shporer, A; Abe, F; Botzler, CS; Fukui, A; Furusawa, K; Hearnshaw, JB; Itow, Y; Korpela, AV; Ling, CH; Masuda, K; Matsubara, Y; Miyake, N; Muraki, Y; Ohnishi, K; Rattenbury, NJ; Saito, T; Sullivan, D; Sumi, T; Suzuki, D; Sweatman, WL; Tristram, PJ; Wada, K; Allan, A; Bode, MF; Bramich, DM; Clay, N; Fraser, SN; Hawkins, E; Kerins, E; Lister, TA; Mottram, CJ; Saunders, ES; Snodgrass, C; Steele, IA; Wheatley, PJ; Bozza, V; Browne, P; Burgdorf, MJ; Calchi Novati, S; Dreizler, S; Finet, F; Glitrup, M; Grundahl, F; Harpsoe, K; Hessman, FV; Hinse, TC; Hundertmark, M; Liebig, C; Maier, G; Mancini, L; Rahvar, S; Ricci, D; Scarpetta, G; Skottfelt, J; Southworth, J; Surdej, J; Zimmer, F

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

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Bachelet, E and Fouque, P and Han, C and Gould, A and Albrow, MD and Beaulieu, J-P and Bertin, E and Bond, IA and Christie, GW and Heyrovski, D and Horne, K and Jorgensen, UG and Maoz, D and Mathiasen, M and Matsunaga, N and McCormick, J and Menzies, J and Nataf, D and Natusch, T and Oi, N and Renon, N and Tsapras, Y and Udalski, A and Yee, JC and Batista, V and Bennett, DP and Brillant, S and Caldwell, JAR and Cassan, A and Cole, A and Cook, KH and Coutures, C and Dieters, S and Dominik, M and Dominis Prester, D and Donatowicz, J and Greenhill, J and Kains, N and Kane, SR and Marquette, J-B and Martin, R and Pollard, KR and Sahu, KC and Street, RA and Wambsganss, J and Williams, A and Zub, M and Bos, M and Dong, S and Drummond, J and Gaudi, BS and Graff, D and Janczak, J and Kaspi, S and Kozlowski, S and Lee, C-U and Monard, LAG and Munoz, JA and Park, B-G and Pogge, RW and Polishook, D and Shporer, A and Abe, F and Botzler, CS and Fukui, A and Furusawa, K and Hearnshaw, JB and Itow, Y and Korpela, AV and Ling, CH and Masuda, K and Matsubara, Y and Miyake, N and Muraki, Y and Ohnishi, K and Rattenbury, NJ and Saito, T and Sullivan, D and Sumi, T and Suzuki, D and Sweatman, WL and Tristram, PJ and Wada, K and Allan, A and Bode, MF and Bramich, DM and Clay, N and Fraser, SN and Hawkins, E and Kerins, E and Lister, TA and Mottram, CJ and Saunders, ES and Snodgrass, C and Steele, IA and Wheatley, PJ and Bozza, V and Browne, P and Burgdorf, MJ and Calchi Novati, S and Dreizler, S and Finet, F and Glitrup, M and Grundahl, F and Harpsoe, K and Hessman, FV and Hinse, TC and Hundertmark, M and Liebig, C and Maier, G and Mancini, L and Rahvar, S and Ricci, D and Scarpetta, G and Skottfelt, J and Southworth, J and Surdej, J and Zimmer, F, A brown dwarf orbiting an M-dwarf: MOA 2009-BLG-411L, Astronomy and Astrophysics, 547 Article A55. ISSN 0004-6361 (2012) [Refereed Article]

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DOI: doi: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.

Item Details

Item Type:	Refereed Article
Keywords:	binaries: general / gravitational lensing: micro / stars: individual: MOA 2009-BLG-411L
Research Division:	Physical Sciences
Research Group:	Astronomical and Space Sciences
Research Field:	Stellar Astronomy and Planetary Systems
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Physical Sciences
UTAS Author:	Cole, A (Associate Professor Andrew Cole)
UTAS Author:	Greenhill, J (Dr John Greenhill)
ID Code:	82637
Year Published:	2012
Web of Science^® Times Cited:	13
Deposited By:	Mathematics and Physics
Deposited On:	2013-02-08
Last Modified:	2017-11-06
Downloads:	344 View Download Statistics

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