CaltechAUTHORS
Published November 2019 | Version Accepted Version + Published
Journal Article Open

WISE J072003.20-084651.2B is a Massive T Dwarf

Creators

  • 1. ROR icon University of Hawaii at Manoa
  • 2. ROR icon The University of Texas at Austin
  • 3. ROR icon University of North Carolina at Chapel Hill
  • 4. ROR icon University of Exeter
  • 5. ROR icon École Normale Supérieure de Lyon
  • 6. ROR icon Institut de Planétologie et d'Astrophysique de Grenoble
  • 7. ROR icon Western University
  • 8. ROR icon Maison de la Simulation
  • 9. ROR icon W.M. Keck Observatory
  • 10. ROR icon California Institute of Technology

Abstract

We present individual dynamical masses for the nearby M9.5+T5.5 binary WISE J072003.20−084651.2AB, a.k.a. Scholz's star. Combining high-precision Canada–France–Hawaii Telescope/WIRCam photocenter astrometry and Keck adaptive optics resolved imaging, we measure the first high-quality parallactic distance (6.80^(+0.05)_(−0.06) pc) and orbit (8.06^(+0.24)_(−0.25) yr period) for this system composed of a low-mass star and brown dwarf. We find a moderately eccentric orbit (e = 0.240^(+0.009)_(−0.010)), incompatible with previous work based on less data, and dynamical masses of 99 ± 6 M_(Jup) and 66 ± 4 M_(Jup) for the two components. The primary mass is marginally inconsistent (2.1σ) with the empirical mass–magnitude–metallicity relation and models of main-sequence stars. The relatively high mass of the cold (T_(eff) = 1250±40 K) brown dwarf companion indicates an age older than a few gigayears, in accord with age estimates for the primary star, and is consistent with our recent estimate of ≈70 M_(Jup) for the stellar/substellar boundary among the field population. Our improved parallax and proper motion, as well as an orbit-corrected system velocity, improve the accuracy of the system's close encounter with the solar system by an order of magnitude. WISE J0720−0846AB passed within 68.7 ± 2.0 kau of the Sun 80.5 ± 0.7 kyr ago, passing through the outer Oort cloud where comets can have stable orbits.

Additional Information

© 2019 The American Astronomical Society. Received 2019 June 7; revised 2019 August 11; accepted 2019 August 18; published 2019 October. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based on data obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, at the Canada–France–Hawaii Telescope, which is operated by the National Research Council of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. T.J.D. acknowledges research support from Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., on behalf of the international Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America. M.C.L. acknowledges National Science Foundation (NSF) grant AST-1518339. The near-infrared pyramid wavefront sensor is supported by NSF grant AST-1611623. The camera used with the pyramid wavefront sensor is provided by Don Hall with support from the National Science Foundation under grant AST-1106391. M.A.T. acknowledges support from the DOE CSGF through grant DE-SC0019323. Our research has employed NASA ADS; SIMBAD; VizieR; and J. R. A. Davenport's IDL implementation of the cubehelix color scheme (Green 2011). Facilities: Keck:II (LGS AO - , NIRC2 - , PyWFS AO) - , CFHT (WIRCam) - , IRTF (SpeX) - , UH:2.2 m (SNIFS). - Software: Spextool (Cushing et al. 2004), emcee (Foreman-Mackey et al. 2013), M_-M_K- (Mann et al. 2019).

Attached Files

Published - Dupuy_2019_AJ_158_174.pdf

Accepted Version - 1908.06994.pdf

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Additional details

Identifiers

Eprint ID
99219
Resolver ID
CaltechAUTHORS:20191010-135451169

Related works

Describes
https://arxiv.org/abs/1908.06994 (URL)

Funding

W. M. Keck Foundation
Gemini Observatory
Association of Universities for Research in Astronomy (AURA)
NSF
AST-1518339
NSF
AST-1611623
NSF
AST-1106391
Department of Energy (DOE)
DE-SC0019323
Department of Energy (DOE)

Dates

Created
2019-10-10
Created from EPrint's datestamp field
Updated
2021-11-16
Created from EPrint's last_modified field

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Caltech groups
Astronomy Department