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Astrometric orbits of spectral binary brown dwarfs – I. Massive T dwarf companions to 2M1059−21 and 2M0805+48

Sahlmann, J. and Burgasser, A. J. and Bardalez Gagliuffi, D. C. and Lazorenko, P. F. and Segransan, D. and Zapatero Osorio, M. R. and Blake, C. H. and Gelino, C. R. and Martín, E. L. and Bouy, H. (2020) Astrometric orbits of spectral binary brown dwarfs – I. Massive T dwarf companions to 2M1059−21 and 2M0805+48. Monthly Notices of the Royal Astronomical Society, 495 (1). pp. 1136-1147. ISSN 0035-8711. doi:10.1093/mnras/staa1235.

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Near-infrared spectroscopic surveys have uncovered a population of short-period, blended-light spectral binaries composed of low-mass stars and brown dwarfs. These systems are amenable to orbit determination and individual mass measurements via astrometric monitoring. Here, we present first results of a multiyear campaign to obtain high-precision absolute astrometry for spectral binaries using the Gemini-South and Gemini-North GMOS imagers. We measure the complete astrometric orbits for two systems: 2M0805+48 and 2M1059−21. Our astrometric orbit of 2M0805+48 is consistent with its 2-yr radial velocity orbit determined previously and we find a mass of 66^(+5)_(−14) M_(Jup) for its T5.5 companion. For 2M1059−21, we find a 1.9-yr orbital period and a mass of 67^(+4)_(−5) M_(Jup) for its T3.5 companion. We demonstrate that sub-milliarcsecond absolute astrometry can be obtained with both GMOS imagers and that this is an efficient avenue for confirming and characterizing ultracool binary systems.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sahlmann, J.0000-0001-9525-3673
Burgasser, A. J.0000-0002-6523-9536
Bouy, H.0000-0002-7084-487X
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 April 30. Received 2020 April 28; in original form 2020 January 31. This research made use of the data bases at the Centre de Données astronomiques de Strasbourg (; of NASA’s Astrophysics Data System Service (; of the paper repositories at arXiv; and of ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013). Based on observations obtained at the Gemini Observatory (acquired through the Gemini Observatory Archive and processed using the Gemini IRAF package and gemini_python), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. ELM acknowledges funding from the Fondo Europeo de Desarrollo Regional (MINECO/FEDER) under grant no. AYA2015-69350-C3-1-P. DBG and AJB acknowledge funding support from the National Aeronautics and Space Administration under Grant No. NNX15AI75G.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2015-69350-C3-1-P
Subject Keywords:binaries: close, brown dwarfs, astrometry, parallaxes, stars: low-mass
Issue or Number:1
Record Number:CaltechAUTHORS:20200625-112850339
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Official Citation:J Sahlmann, A J Burgasser, D C Bardalez Gagliuffi, P F Lazorenko, D Ségransan, M R Zapatero Osorio, C H Blake, C R Gelino, E L Martín, H Bouy, Astrometric orbits of spectral binary brown dwarfs – I. Massive T dwarf companions to 2M1059−21 and 2M0805+48, Monthly Notices of the Royal Astronomical Society, Volume 495, Issue 1, June 2020, Pages 1136–1147,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104053
Deposited By: George Porter
Deposited On:25 Jun 2020 21:09
Last Modified:16 Nov 2021 18:27

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