Journal
ASTROPHYSICAL JOURNAL
Volume 763, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/763/1/67
Keywords
brown dwarfs; gravitational lensing: micro; planetary systems; planets and satellites: formation; planets and satellites: general; techniques: photometric
Categories
Funding
- Qatar Foundation, QNRF [NPRP-09-476-1-078]
- National Research Foundation of Korea [2009-0081561]
- European Union [268421]
- European Research Council under European Community [246678]
- National Aeronautics and Space Administration
- National Science Foundation
- Korea Research Council for Fundamental Science and Technology (KRCF) through Young Research Scientist Fellowship Program
- KASI (Korea Astronomy and Space Science Institute) [2012-1-410-02]
- Communaute francaise de Belgique-Actions de recherche concertees-Academie universitaire Wallonie-Europe
- NSF [AST-1103471, AST-0807444]
- NASA [NNX12AB99G]
- National Science Foundation Graduate Research Fellowship [2009068160]
- Ralph E. and Doris M. Hansmann Membership at the IAS
- [JSPS20340052]
- [JSPS22403003]
- [JSPS19340058]
- STFC [PP/E001149/1, ST/G002355/1, ST/G001987/1, ST/K002465/1, ST/J001651/1, ST/J001384/1, PP/D000955/1, ST/J001562/1, PP/F000057/1, ST/H002391/1, ST/G009465/1, ST/J001465/1, ST/J000035/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/H002391/1, ST/J001465/1, ST/J001384/1, ST/G001987/1, PP/F000057/1, ST/G009465/1, PP/E001149/1, ST/J001651/1, PP/D000955/1, ST/J001562/1, ST/G002355/1, ST/J000035/1] Funding Source: researchfish
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1009621, 807444, 1211875] Funding Source: National Science Foundation
- Grants-in-Aid for Scientific Research [23540339, 23340064, 23654082, 23340044] Funding Source: KAKEN
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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)(S),(0), is 1.221 +/- 0.051 mag, and from our lens model we derive a source radius of 14.7 +/- 1.3 R-circle dot, 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(E) = 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-L = 2.8 +/- 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with M-L,M-1 = 0.16 +/- 0.03 M-circle dot, while the companion has M-L,M-2 = 11.0 +/- 2.0 M-J, putting it in the boundary zone between planets and brown dwarfs.
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