MICROLENSING DISCOVERY OF A POPULATION OF VERY TIGHT, VERY LOW MASS BINARY BROWN DWARFS

Journal Article · Fri May 10 00:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/768/2/129· OSTI ID:22126742

Choi, J. -Y.; Han, C. ^[1]; Udalski, A. ^[2]; Sumi, T. ^[3]; Gaudi, B. S.; Gould, A. ^[4]; Bennett, D. P. ^[5]; Dominik, M. ^[6]; Beaulieu, J. -P. ^[7]; Tsapras, Y. ^[8]; Bozza, V. ^[9]; Abe, F.; Furusawa, K.; Itow, Y. ^[10]; Bond, I. A.; Ling, C. H. ^[11]; Botzler, C. S.; Freeman, M. ^[12]; Chote, P. ^[13]; Fukui, A. ^[14] ; Consortium, MiNDSTEp; others, and

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1. Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of)
2. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)
3. Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan)
4. Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
5. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556-5670 (United States)
6. SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)
7. Institut dAstrophysique de Paris, UMR7095 CNRS-Universite Pierre and Marie Curie, 98 bis boulevard Arago, F-75014 Paris (France)
8. Las Cumbres Observatory Global Telescope Network, 6740B Cortona Drive, Goleta, CA 93117 (United States)
9. INFN, Sezione di Napoli, I-80126 Napoli (Italy)
10. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)
11. Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland 0745 (New Zealand)
12. Department of Physics, University of Auckland, Private Bag 92-019, Auckland 1001 (New Zealand)
13. School of Chemical and Physical Sciences, Victoria University, Wellington 6140 (New Zealand)
14. Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan)

Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs (BDs) are poorly understood. The multiplicity properties and minimum mass of the BD mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very low mass, very tight binary systems. These binaries have directly and precisely measured total system masses of 0.025 M{sub Sun} and 0.034 M{sub Sun }, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field BD binaries known. The discovery of a population of such binaries indicates that BD binaries can robustly form at least down to masses of {approx}0.02 M{sub Sun }. Future microlensing surveys will measure a mass-selected sample of BD binary systems, which can then be directly compared to similar samples of stellar binaries.

• OSTI ID: 22126742
• Journal Information: Astrophysical Journal, Vol. 768, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BINARY STARS
DWARF STARS
GRAVITATIONAL LENSES
MASS
MULTIPLICITY