Parallaxes of Southern Extremely Cool objects III: 118 L and T dwarfs

R. L. Smart*, B. Bucciarelli, H. R.A. Jones, F. Marocco, A. H. Andrei, B. Goldman, R. A. Mendez, V. A. d'Avila, B. Burningham, J. I.B. Camargo, M. T. Crosta, M. Daprà, J. S. Jenkins, R. Lachaume, M. G. Lattanzi, J. L. Penna, D. J. Pinfield, D. N. da Silva Neto, A. Sozzetti, A. Vecchiato

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


We present new results from the Parallaxes of Southern Extremely Cool dwarfs program to measure parallaxes, proper motions and multiepoch photometry of L and early T dwarfs. The observations were made on 108 nights over the course of 8 yr using the Wide Field Imager on the ESO 2.2m telescope. We present 118 new parallaxes of L and T dwarfs of which 52 have no published values and 24 of the 66 published values are preliminary estimates from this program. The parallax precision varies from 1.0 to 15.5mas with a median of 3.8mas. We find evidence for two objects with long term photometric variation and 24 new moving group candidates. We cross-match our sample to published photometric catalogues and find standard magnitudes in up to 16 pass-bands from which we build spectral energy distributions and H-R diagrams. This allows us to confirm the theoretically anticipated minimum in radius between stars and brown dwarfs across the hydrogen burning minimum mass. We find the minimum occurs between L2 and L6 and verify the predicted steep dependence of radius in the hydrogen burning regime and the gentle rise into the degenerate brown dwarf regime. We find a relatively young age of ~2 Gyr from the kinematics of our sample.

Original languageEnglish
Pages (from-to)3548-3562
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date14 Sept 2018
Publication statusPublished - 11 Dec 2018


RLS was supported by a Henri Chrétien International Research Grant administered by the American Astronomical Society and a Visiting Professorship with the Leverhulme Trust (VP1-2015-063). FM/HRAJ/DJP acknowledge support from the UK’s Science and Technology Facilities Council grant number ST/M001008/1. FM was supported by an appointment to the NASA Postdoctoral Program the the Jet Propulsion Laboratory, administered by the Universities Space Research Association under contract with NASA. AHA/RLS were supported by the Marie Curie 7th European Community Framework Programme grant no. 236735 Parallaxes of Southern Extremely Cool objects (PARSEC) International Incoming Fellowship and grant no. 247593 Interpretation and Parameterisation of Extremely Red COOL dwarfs (IPERCOOL) International Research Staff Exchange Scheme. RAM acknowledges support from the Chilean Centro de Excelencia en Astrofisica y Tecnolo-gias Afines (CATA) BASAL PFB/06, from the Project IC120009 Millennium Institute of Astrophysics of the Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo de Chile, and from CONICYT/FONDECYT Grant Nr. 117 0854. This research is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile programs 079.A-9203, 081.A-9200, 082.C-0946, 083.C-0446, 085.C-0690, 086.C-0168, and 186.C-0756; in proposal 15B/54 of OPTICON funded under EU FP6 contract number RII3-CT-001566; through CNTAC in proposal CN2015B–5; the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovac¸ão (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU) as part of the proposals SO2009A-008, SO2011A-009, and SO2011B-006.

FundersFunder number
Chilean Centro de Excelencia en Astrofisica y Tecnolo-gias Afines
EU FP6RII3-CT-001566
Henri Chrétien International Research
Marie Curie 7th European Community Framework Programme247593, 236735
Universities Space Research Association
National Aeronautics and Space Administration
University of North Carolina
Michigan State UniversitySO2009A-008, SO2011B-006, SO2011A-009
University of North Carolina at Chapel Hill
American Astronomical Society
Science and Technology Facilities CouncilST/M001008/1
Leverhulme TrustVP1-2015-063
Ministério da Ciência, Tecnologia e Inovação
Centro de Astrofísica y Tecnologías AfinesBASAL PFB/06, IC120009
Ministerio de Economía, Fomento y Turismo
China National Textile and Apparel Council
Centre for Southern Hemisphere Oceans Research082.C-0946, 085.C-0690, 186.C-0756, 086.C-0168, 083.C-0446, 081.A-9200


    • Brown dwarfs
    • Parallaxes
    • Proper motions
    • Stars: low-mass


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