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Journal Paper

전체
KMT-2016-BLG-2052L: Microlensing Binary Composed of M Dwarfs Revealed from a Very Long Timescale Event SCI
  • Cheongho Han;Yeon Kil Jung;Yossi Shvartzvald;Michael D. Albrow;Chung, Sun-Ju;Andrew P. Gould;Kyu-Ha Hwang;Doeon Kim;Lee Chung-uk;WoongTae Kim;Kim Hyoun-Woo;Ryu, Yoon-Hyun;InGu Shin;Jennifer C. Yee;ChunHwey Kim;Cha Sang-Mok;Kim Seung-Lee;Dong-jin Kim;Lee Dongjoo;Yongseok Lee;PARK, BYEONG GON;Richard W. Pogge;Charles Beichman;Geoff Bryden;Sebastiano Calchi Novati;B. Scott Gaudi;Calen B. Henderson;T. P. Matthew;Savannah R. Jacklin
  • 2018-09-20
  • THE ASTROPHYSICAL JOURNAL 865 1 : 14-1~14-9
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 gsim 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.