Dynamical mass of GJ 802B : a brown dwarf in a triple system

Creators: Ireland, M. J.; Kraus, A.; Martinache, F.; Lloyd, J. P.; Tuthill, P. G.

Abstract

We report a dynamical measurement of the mass of the brown dwarf GJ 802B using aperture-masking interferometry and astrometry. In addition, we report the discovery that GJ 802A is itself a close spectroscopic noneclipsing binary with a 19 hr period. We find the mass of GJ 802B to be 0:063 ± 0:005M⊙. GJ 802 has kinematics inconsistent with a young star and more consistent with the thick-disk population, implying a system age of ~10 Gyr. However, model evolutionary tracks for GJ 802B predict system ages of ~2 Gyr, suggesting that brown dwarf evolutionary models may be underestimating luminosity for old brown dwarfs.

Additional Information

© 2008. The American Astronomical Society. Received 2007 October 9; accepted 2008 January 9. M. J. I. would like to acknowledge Michelson Fellowship support from the Michelson Science Center and the NASA Navigator Program. A. L. K. is supported by a NASA Origins grant to L. Hillenbrand. This work is partially supported by the National Science Foundation under grants AST 05-06588 and AST 07-05085. Some of the 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. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Based partly on observations obtained at theHale Telescope, Palomar Observatory, as part of a collaborative agreement between the California Institute of Technology, its divisions Caltech Optical Observatories and the Jet Propulsion Laboratory (operated for NASA), and Cornell University. Based partly on observations obtained at the Palomar 60 inch robotic telescope.

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