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KMT-2016-BLG-1820 and KMT-2016-BLG-2142: Two Microlensing Binaries Composed of Planetary-mass Companions and Very-low-mass Primaries

Jung, Youn Kil and Hwang, Kyu-Ha and Ryu, Yoon-Hyun and Gould, Andrew and Han, Cheongho and Yee, Jennifer C. and Albrow, Michael D. and Chung, Sun-Ju and Shin, In-Gu and Shvartzvald, Yossi and Zang, Weicheng and Cha, Sang-Mok and Kim, Dong-Jin and Kim, Hyoun-Woo and Kim, Seung-Lee and Lee, Chung-Uk and Lee, Dong-Joo and Lee, Yongseok and Park, Byeong-Gon and Pogge, Richard W. (2018) KMT-2016-BLG-1820 and KMT-2016-BLG-2142: Two Microlensing Binaries Composed of Planetary-mass Companions and Very-low-mass Primaries. Astronomical Journal, 156 (5). Art. No. 208. ISSN 1538-3881. doi:10.3847/1538-3881/aae319.

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We present the analyses of two short-timescale (t_E ~ 5 days) 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 θ_E = 0.12 mas, 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 0.043^(+0.043)_(-0.018) M⊙ And 0.088^(+0.120)_(-0.041) M⊙, 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 7 kpc. 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Jung, Youn Kil0000-0002-0314-6000
Hwang, Kyu-Ha0000-0002-9241-4117
Ryu, Yoon-Hyun0000-0001-9823-2907
Han, Cheongho0000-0002-2641-9964
Yee, Jennifer C.0000-0001-9481-7123
Albrow, Michael D.0000-0003-3316-4012
Chung, Sun-Ju0000-0001-6285-4528
Shin, In-Gu0000-0002-4355-9838
Shvartzvald, Yossi0000-0003-1525-5041
Zang, Weicheng0000-0001-6000-3463
Kim, Hyoun-Woo0000-0001-8263-1006
Pogge, Richard W.0000-0003-1435-3053
Additional Information:© 2018 The American Astronomical Society. Received 2018 May 24; revised 2018 August 30; accepted 2018 September 18; published 2018 October 18. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. C.H. was supported by grant 2017R1A4A1015178 of the National Research Foundation of Korea. Work by W.Z. and A.G. were supported by AST-1516842 from the US NSF. W.Z. and A.G. were supported by JPL grant 1500811. A.G. is supported from KASI grant 2016-1-832-01.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Research Foundation of Korea2017R1A4A1015178
Korea Astronomy and Space Science Institute (KASI)2016-1-832-01
Subject Keywords:binaries: general – brown dwarfs – gravitational lensing: micro
Issue or Number:5
Record Number:CaltechAUTHORS:20181023-085513933
Persistent URL:
Official Citation:Youn Kil Jung et al 2018 AJ 156 208
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90347
Deposited By: Tony Diaz
Deposited On:23 Oct 2018 21:50
Last Modified:16 Nov 2021 03:31

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