DETERMINING THE PHYSICAL LENS PARAMETERS OF THE BINARY GRAVITATIONAL MICROLENSING EVENT MOA-2009-BLG-016

Journal Article · Thu Jul 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/717/1/435· OSTI ID:21452862

Hwang, K -H; Han, C ^[1]; Bond, I A; Lin, W; Ling, C H ^[2]; Miyake, N; Abe, F; Fukui, A; Furusawa, K; Hayashi, F; Hosaka, S; Itow, Y; Kamiya, K; Makita, S; Masuda, K ^[3]; Bennett, D P ^[4]; Botzler, C S ^[5]; Hearnshaw, J B ^[6]; Kilmartin, P M ^[7]; Korpela, A ^[8]

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1. Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)
2. Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand)
3. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)
4. Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)
5. Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand)
6. Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8020 (New Zealand)
7. Mt. John Observatory, P.O. Box 56, Lake Tekapo 8770 (New Zealand)
8. School of Chemical and Physical Sciences, Victoria University, Wellington (New Zealand)

We report the result of the analysis of the light curve of the microlensing event MOA-2009-BLG-016. The light curve is characterized by a short-duration anomaly near the peak and an overall asymmetry. We find that the peak anomaly is due to a binary companion to the primary lens and the asymmetry of the light curve is explained by the parallax effect caused by the acceleration of the observer over the course of the event due to the orbital motion of the Earth around the Sun. In addition, we detect evidence for the effect of the finite size of the source near the peak of the event, which allows us to measure the angular Einstein radius of the lens system. The Einstein radius combined with the microlens parallax allows us to determine the total mass of the lens and the distance to the lens. We identify three distinct classes of degenerate solutions for the binary lens parameters, where two are manifestations of the previously identified degeneracies of close/wide binaries and positive/negative impact parameters, while the third class is caused by the symmetric cycloid shape of the caustic. We find that, for the best-fit solution, the estimated mass of the lower-mass component of the binary is (0.04 {+-} 0.01) M{sub sun}, implying a brown-dwarf companion. However, there exists a solution that is worse only by {Delta}{chi}{sup 2} {approx} 3 for which the mass of the secondary is above the hydrogen-burning limit. Unfortunately, resolving these two degenerate solutions will be difficult as the relative lens-source proper motions for both are similar and small ({approx}1 mas yr{sup -1}) and thus the lens will remain blended with the source for the next several decades.

• OSTI ID: 21452862
• Journal Information: Astrophysical Journal, Vol. 717, Issue 1; Other Information: DOI: 10.1088/0004-637X/717/1/435; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASYMMETRY
HYDROGEN BURNING
IMPACT PARAMETER
PROPER MOTION
SUN
MAIN SEQUENCE STARS
MOTION
STAR BURNING
STARS