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Spitzer Microlensing Parallax for OGLE-2017-BLG-0896 Reveals a Counter-Rotating Low-Mass Brown Dwarf

Shvartzvald, Yossi and Yee, Jennifer C. and Skowron, Jan and Lee, Chung-Uk and Udalski, Andrzej and Calchi Novati, Sebastiano and Bozza, Valerio and Beichman, Charles A. and Bryden, Geoffery and Carey, Sean and Gaudi, B. Scott and Henderson, Calen B. and Zhu, Wei and Bachelet, Etienne and Bolt, Greg and Christie, Grant and Maoz, Dan and Natusch, Tim and Pogge, Richard W. and Street, Rachel A. and Tan, Thiam-Guan and Tsapras, Yiannis and Pietrukowicz, Paweł and Soszyński, Igor and Szymański, Michał K. and Mróz, Przemek and Poleski, Radoslaw and Kozłowski, Szymon and Ulaczyk, Krzysztof and Pawlak, Michał and Rybicki, Krzysztof A. and Iwanek, Patryk and Albrow, Michael D. and Cha, Sang-Mok and Chung, Sun-Ju and Gould, Andrew and Han, Cheongho and Hwang, Kyu-Ha and Jung, Youn Kil and Kim, Dong-Jin and Kim, Hyoun-Woo and Kim, Seung-Lee and Lee, Dong-Joo and Lee, Yongseok and Park, Byeong-Gon and Ryu, Yoon-Hyun and Shin, In-Gu and Zang, Weicheng and Dominik, Martin and Helling, Christiane and Hundertmark, Markus and Jørgensen, Uffe G. and Longa-Peña, Penelope and Lowry, Stephen and Sajadian, Sedighe and Burgdorf, Martin J. and Campbell-White, Justyn and Ciceri, Simona and Evans, Daniel F. and Fujii, Yuri I. and Hinse, Tobias C. and Rahvar, Sohrab and Rabus, Markus and Skottfelt, Jesper and Snodgrass, Colin and Southworth, John (2019) Spitzer Microlensing Parallax for OGLE-2017-BLG-0896 Reveals a Counter-Rotating Low-Mass Brown Dwarf. Astronomical Journal, 157 (3). Art. No. 106. ISSN 1538-3881. doi:10.3847/1538-3881/aafe12.

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The kinematics of isolated brown dwarfs in the Galaxy, beyond the solar neighborhood, is virtually unknown. Microlensing has the potential to probe this hidden population, as it can measure both the mass and five of the six phase-space coordinates (all except the radial velocity) even of a dark isolated lens. However, the measurements of both the microlens-parallax and finite-source effects are needed in order to recover the full information. Here, we combine the Spitzer satellite parallax measurement with the ground-based light curve, which exhibits strong finite-source effects, of event OGLE-2017-BLG-0896. We find two degenerate solutions for the lens (due to the known satellite-parallax degeneracy), which are consistent with each other except for their proper motion. The lens is an isolated brown dwarf with a mass of either 18 ± 1 M_J or 20 ± 1 M_J . This is the lowest isolated-object mass measurement to date, only ~45% more massive than the theoretical deuterium-fusion boundary at solar metallicity, which is the common definition of a free-floating planet. The brown dwarf is located at either 3.9 ± 0.1 kpc or 4.1 ± 0.1 kpc toward the Galactic bulge, but with proper motion in the opposite direction of disk stars, with one solution suggesting it is moving within the Galactic plane. While it is possibly a halo brown dwarf, it might also represent a different, unknown population.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Shvartzvald, Yossi0000-0003-1525-5041
Calchi Novati, Sebastiano0000-0002-7669-1069
Beichman, Charles A.0000-0002-5627-5471
Carey, Sean0000-0002-0221-6871
Henderson, Calen B.0000-0001-8877-9060
Additional Information:© 2019 The American Astronomical Society. Received 2018 May 22; revised 2019 January 8; accepted 2019 January 10; published 2019 February 11. We thank D. Kirkpatrick for fruitful discussions about BDs. Work by Y.K.J. and A.G. was supported by AST-1516842 from the US NSF. I.G.S. and A.G. were supported by JPL grant 1500811. Work by C. Han was supported by the grant (2017R1A4A1015178) of the National Research Foundation of Korea. This work is based (in part) on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work was partially supported by NASA contract NNG16PJ32C. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. Work by S.R. and S.S. was supported by INSF-95843339. P.L.-P. was supported by MINEDUC-UA project, code ANT 1656. The research has made use of data obtained at the Danish 1.54 m telescope at ESOs La Silla Observatory.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Research Foundation of Korea2017R1A4A1015178
National Science Centre (Poland)2014/14/A/ST9/00121
Iran National Science Foundation95843339
MINEDUC-UA ProjectANT 1656
Subject Keywords:Galaxy: bulge – gravitational lensing: micro
Issue or Number:3
Record Number:CaltechAUTHORS:20190201-160924334
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Official Citation:Yossi Shvartzvald et al 2019 AJ 157 106
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92616
Deposited By: George Porter
Deposited On:02 Feb 2019 00:25
Last Modified:16 Nov 2021 03:52

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