Volume 604, August 2017
|Number of page(s)||8|
|Section||Planets and planetary systems|
|Published online||18 August 2017|
A companion on the planet/brown dwarf mass boundary on a wide orbit discovered by gravitational microlensing
1 Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA
2 Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
3 Institute for Natural and Mathematical Sciences, Massey University, Private Bag 102904 North Shore Mail Centre, 0745 Auckland, New Zealand
4 Sorbonne Universités, UPMC Univ. Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis bd Arago, 75014 Paris, France
5 LESIA Observatoire de Paris, Section de Meudon, 5 place Jules Janssen, 92195 Meudon, France
6 School of Physical Sciences, University of Tasmania, Private Bag 37 Hobart, 7001 Tasmania, Australia
7 NASA Ames Research Center, Space Science & Astrobiology Division, Moffett Field, CA 94035, USA
8 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
9 Laboratory for Exoplanets and Stellar Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
10 Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonake, 560-0043 Osaka, Japan
11 Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
12 Institute of Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa, Nagoya, 464-8601 Aichi, Japan
13 Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA
14 Okayama Astrophysical National Astronomical Observatory, 3037-5 Honjo, Kamogata, Asakuchi, 719-0232 Okayama, Japan
15 Nagano National College of Technology, 381-8550 Nagano, Japan
16 Tokyo Metropolitan College of Industrial Technology, 116-8523 Tokyo, Japan
17 School of Chemical and Physical Sciences, Victoria University, Wellington, New Zealand
18 University of Canterbury Mt John Observatory, PO Box 56, 7945 Lake Tekapo, New Zealand
19 Department of Physics, Faculty of Science, Kyoto Sangyo University, 603-8555 Kyoto, Japan
Received: 3 April 2017
Accepted: 4 May 2017
We present the discovery of a substellar companion to the primary host lens in the microlensing event MOA-2012-BLG-006. The companion-to-host mass ratio is 0.016, corresponding to a companion mass of ≈8 MJup(M∗/ 0.5 M⊙). Thus, the companion is either a high-mass giant planet or a low-mass brown dwarf, depending on the mass of the primary M∗. The companion signal was separated from the peak of the primary event by a time that was as much as four times longer than the event timescale. We therefore infer a relatively large projected separation of the companion from its host of ≈10 au(M∗/ 0.5 M⊙)1 / 2 for a wide range (3–7 kpc) of host star distances from the Earth. We also challenge a previous claim of a planetary companion to the lens star in microlensing event OGLE-2002-BLG-045.
Key words: gravitational lensing: micro / instrumentation: high angular resolution / planetary systems / brown dwarfs
© ESO, 2017
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