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KMT-2016-BLG-2052L: Microlensing Binary Composed of M Dwarfs Revealed from a Very Long Timescale Event

Han, Cheongho and Shvartzvald, Yossi and Calchi Novati, Sebastiano and Beichman, Charles and Henderson, Calen B. (2018) KMT-2016-BLG-2052L: Microlensing Binary Composed of M Dwarfs Revealed from a Very Long Timescale Event. Astrophysical Journal, 865 (1). Art. No. 14. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20180917-160339137

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Abstract

We present the analysis of a binary microlensing event, KMT-2016-BLG-2052, for which the lensing-induced brightening of the source star lasted for two seasons. We determine the lens mass from the combined measurements of the microlens parallax, π_E, and angular Einstein radius, θ_E. The measured mass indicates that the lens is a binary composed of M dwarfs with masses of M_1 ~ 0.34 M⊙ and M_2 ~ 0.17 M⊙. The measured relative lens-source proper motion of μ ~ 3.9 mas yr^(−1) is smaller than ~5 mas yr−1 of typical Galactic lensing events, while the estimated angular Einstein radius of θ E ~ 1.2 mas is substantially greater than the typical value of ~0.5 mas. Therefore, it turns out that the long timescale of the event is caused by the combination of the slow μ and large θ_E rather than the heavy mass of the lens. From the simulation of Galactic lensing events with very long timescales (t_E ≳ 100 days), we find that the probabilities that long timescale events are produced by lenses with masses ≥1.0 M⊙ and ≥3.0 M⊙ are ~19% and 2.6%, respectively, indicating that events produced by heavy lenses comprise a minor fraction of long timescale events. The results indicate that it is essential to determine lens masses by measuring both π_E and θ_E in order to firmly identify heavy stellar remnants, such as neutron stars and black holes.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/aad699DOIArticle
https://arxiv.org/abs/1807.11132arXivDiscussion Paper
ORCID:
AuthorORCID
Han, Cheongho0000-0002-2641-9964
Shvartzvald, Yossi0000-0003-1525-5041
Calchi Novati, Sebastiano0000-0002-7669-1069
Beichman, Charles0000-0002-5627-5471
Henderson, Calen B.0000-0001-8877-9060
Additional Information:© 2018 The American Astronomical Society. Received 2018 July 13; revised 2018 July 23; accepted 2018 July 27; published 2018 September 17. Work by C.H. was supported by the grant (2017R1A4A1015178) of National Research Foundation of Korea. Work by A.G. was supported by JPL grant 1500811 and US NSF grant AST-1516842. Work by J.C.Y. was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. 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.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
National Research Foundation of Korea2017R1A4A1015178
JPL1500811
NSFAST-1516842
NASA/JPL/CaltechUNSPECIFIED
NASA Sagan FellowshipUNSPECIFIED
Subject Keywords:binaries: general – gravitational lensing: micro
Issue or Number:1
Record Number:CaltechAUTHORS:20180917-160339137
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180917-160339137
Official Citation:Cheongho Han et al 2018 ApJ 865 14
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89692
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Sep 2018 23:51
Last Modified:24 Feb 2020 10:30

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