MOA-2015-BLG-337: A Planetary System with a Low-mass Brown Dwarf/Planetary Boundary Host, or a Brown Dwarf Binary
Year: 2018
Type: article
Abstract: We report on the discovery and analysis of the short-timescale binary-lens microlensing event, MOA-2015-BLG-337. The lens system could be a planetary system with a very low-mass host, around the brown dwarf (BD)/planetary-mass boundary, or a BD binary. We found two competing models that explain the observed light curves with companion/host mass ratios of q ∼ 0.01 and ∼0.17, respectively. A significant finite source effect in the best-fit planetary model (q ∼ 0.01) reveals a small angular Einstein radius of θ E ≃ 0.03 mas, which favors a low-mass lens. We obtain the posterior probability distribution of the lens properties from a Bayesian analysis. The results for the planetary models strongly depend on a power-law index in planetary-mass regime, α pl, in the assumed mass function. In summary, there are two solutions of the lens system: (1) a BD/planetary-mass boundary object orbited by a super-Neptune (the planetary model with α pl = 0.49) and (2) a BD binary (the binary model). If the planetary models are correct, this system can be one of a new class of planetary system, having a low host mass and also a planetary-mass ratio (q < 0.03) between the companion and its host. The discovery of the event is important for the study of planetary formation in very low-mass objects. In addition, it is important to consider all viable solutions in these kinds of ambiguous events in order for the future comprehensive statistical analyses of planetary/binary microlensing events.
Source: The Astronomical Journal
Authors: S. Miyazaki, T. Sumi, D. P. Bennett, A. Gould, A. Udalski, I. A. Bond, N. Koshimoto, M. Nagakane, N. Rattenbury, F. Abe, A. Bhattacharya, R. Barry, M. Donachie, A. Fukui, Y. Hirao, Y. Itow, K. Kawasaki, M. C. A. Li, C. H. Ling, Y. Matsubara, T. Matsuo, Y. Muraki, K. Ohnishi, C. Ranc, T. Saito, A. Sharan, H. Shibai, H. Suematsu, D. Suzuki, D. J. Sullivan, P. J. Tristram, T. Yamada, A. Yonehara, S. KozŁowski, P. Mróz, M. Pawlak, R. Poleski, P. Pietrukowicz, J. Skowron, I. Soszyński, M. K. Szymański, K. Ulaczyk, M. D. Albrow, S.-J. Chung, C. Han, Y. K. Jung, K.-H. Hwang, Y.-H. Ryu, I.-G. Shin, Y. Shvartzvald, J. C. Yee, W. Zang, W. Zhu, S.-M. Cha, D.-J. Kim, H.-W. Kim, S.-L. Kim, C.-U. Lee, D.-J. Lee, Y. Lee, B.-G. Park, R. W. Pogge
Institutions: The University of Osaka, University of Notre Dame, Goddard Space Flight Center, Korea Astronomy and Space Science Institute, Max Planck Institute for Astronomy, The Ohio State University, University of Warsaw, Massey University, University of Auckland, Institute for Space-Earth Environmental Research, Nagoya University, Nagoya University, National Astronomical Observatory of Japan, National Institute of Technology, Nagano College, Tokyo Metropolitan College of Industrial Technology, Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Victoria University of Wellington, University of Canterbury, Kyoto Sangyo University, Korea University of Science and Technology, Chungbuk National University, Center for Astrophysics Harvard & Smithsonian, Jet Propulsion Laboratory, Zhejiang University, Tsinghua University, University of Toronto, Canadian Institute for Theoretical Astrophysics, Kyung Hee University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, National Aeronautics and Space Administration, Universities Space Research Association, National Research Foundation, Royal Society Te Apārangi, Korea Astronomy and Space Science Institute, National Research Foundation of Korea, Narodowym Centrum Nauki, Goddard Space Flight Center, Science and Technology Facilities Council, Japan Society for the Promotion of Science
Awards: 重力マイクロレンズ法による惑星存在率の銀河系内分布及び主星質量依存性の推定, The Mass Function and Galactic Distribution of Cool Planets from Microlensing, Doctoral Dissertation Research: Using Ethnographic Methods to Document the Garifuna Language, Microlensing Survey for Exoplanets beyond the Snow Line, G4211331249, 重力マイクロレンズ法によるＭ型星周りの地球質量～恒星質量までの伴星の存在量の制限, G5150637781, Search for extrasolar planets with microlensing, G6439275480, Warwick Astronomy and Astrophysics Consolidated Grant 2017-2020, G6996030003, 世界初の近赤外線による重力マイクロレンズ法を用いた系外惑星探査, Search for cold exoplanets and free-floating planets by near infrared gravitational microlensing observation, G7558095811, G7768689371
OpenAlex ID: W2795516670