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标题：KMT-2016-BLG-1820 and KMT-2016-BLG-2142: Two Microlensing Binaries Composed of Planetary-mass Companions and Very-low-mass Primaries
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作者：Youn Kil Jung ; Kyu-Ha Hwang ; Yoon-Hyun Ryu 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：156
期号：5
页码：1-8
DOI：10.3847/1538-3881/aae319
语种：English
出版社：American Institute of Physics
摘要：We present the analyses of two short-timescale ~ ( ) t 5 days E microlensing events, KMT-2016-BLG-1820 and KMT-2016-BLG-2142. In both light curves, the brief anomalies were clearly captured and densely covered by the Korea Microlensing Telescope Network survey. From these analyses, we find that both events have small Einstein radii of q = 0.12 mas E , suggesting that the binary-lens systems are composed of very-low-mass components and/ or are located much closer to the lensed stars than to Earth. From Bayesian analyses, we find that these binaries have total system masses of - + M 0.043 0.018 0.043 and - + M 0.088 0.041 0.120 , implying that they are well within the very-low-mass regime. The estimated lens-component masses indicate that the binary lenses consist of a giant-planet/brown-dwarf pair (KMT-2016-BLG-1820) and a dark/faint object pair (KMT-2016-BLG-2140) that are located near the deuterium-burning and hydrogen-burning mass limits, respectively. Both lens systems are likely to be in the Galactic disk with estimated distances of about 6 and 7kpc. The projected lens-components separations are 1.1 and 0.8 au, and the mass ratios are 0.11 and 0.20. These prove that the microlensing method is effective to identify these closely separated very-low-mass binaries having low mass-ratios.
关键词：binaries: general;brown dwarfs;gravitational lensing: micro