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Published March 1, 2000 | Published
Journal Article Open

Discovery of a Brown Dwarf Companion to Gliese 570ABC: A 2MASS T Dwarf Significantly Cooler than Gliese 229B


We report the discovery of a widely separated (258".3 ± 0".4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All-Sky Survey. Its near-infrared spectrum shows the 1.6 and 2.2 μm CH_4 absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (M_J = 16.47 ± 0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L = (2.8 ± 0.3) × 10^(-6) L_☉ and T_(eff) = 750 ± 50 K make it significantly cooler and less luminous than any other known brown dwarf companion. Using evolutionary models by Burrows et al. and an adopted age of 2-10 Gyr, we derive a mass estimate of 50 ± 20 M_(Jup) for this object.

Additional Information

© 2000 American Astronomical Society. Received 1999 November 22; accepted 2000 January 11; published 2000 February 10. A. J. B. acknowledges Robert Blum and Ron Probst for their guidance at the telescope and in the reduction process, the capable assistance of CTIO telescope operators Mauricio Fernandez and Alberto Zúniga, useful discussions with Mark Marley, helpful comments from the anonymous referee, and Daniel Durand for dealing with high volumes of image requests on the CADC DSS server. We thank the 2MASS staff and scientists for their efforts in creating a truly incredible astronomical resource. DSS images were obtained from the Canadian Astronomy Data Centre, which is operated by the Herzberg Institute of Astrophysics, National Research Council of Canada. A. J. B., J. D. K., I. N. R., and J. L. acknowledge funding through a NASA/JPL grant to 2MASS Core Project science. A. J. B., J. D. K., R. M. C., and C. A. B. acknowledge the support of the Jet Propulsion Laboratory, California Institute of Technology, which is operated under contract with the National Aeronautics and Space Administration. This publication makes use of data from the Two Micron All-Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation.

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