The Bulletin of The Korean Astronomical Society (천문학회보)

The Korean Astronomical Society (한국천문학회)
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OGLE-2015-BLG-1482L:The first isolated Galactic bulge microlens

  • Chung, Sun-Ju (Korea Astronomy and Space Science Institute) ;
  • Zhu, Wei (Department of Astronomy, Ohio State University) ;
  • Udalski, Andrzej (Warsaw University Observatory,) ;
  • Lee, Chung-Uk (Korea Astronomy and Space Science Institute) ;
  • Ryu, Yoon-Hyun (Korea Astronomy and Space Science Institute) ;
  • Jung, Youn Kil (Harvard-Smithsonian Center for Astrophysics) ;
  • Shin, In-Gu (Harvard-Smithsonian Center for Astrophysics) ;
  • Yee, Jennifer C. (Harvard-Smithsonian Center for Astrophysics) ;
  • Hwang, Kyu-Ha (Korea Astronomy and Space Science Institute) ;
  • Gould, Andrew (Korea Astronomy and Space Science Institute)
  • Published : 2017.04.10
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Abstract

The single lens event OGLE-2015-BLG-1482 has been simultaneously observed from two ground-based surveys and from Spitzer. The Spitzer data exhibit finite-source effects due to the passage of the lens close to or directly over the surface of the source star as seen from Spitzer. Thanks to measurements of the microns parallax and the finite-source effect, we find that the lens of OGLE-2015-BLG-1482 is a very low-mass star with the mass $0.10{\pm}0.02M{\odot}$ or a brown dwarf with the mass $55{\pm}9MJ$, which are respectively located at $DLS=0.80{\pm}0.19kpc$ and $DLS=0.54{\pm}0.08kpc$, and thus it is the first isolated low-mass microlens that has been located in the Galactic bulge. The degeneracy between the two solutions is severe. The fundamental reason for the degeneracy is that the finite-source effect is seen only in a single data point from Spitzer and this single data point gives rise to two ${\rho}$ solutions.

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