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Title:
SDSS J1534+1615AB: A Novel T Dwarf Binary Found with Keck Laser Guide Star Adaptive Optics and the Potential Role of Binarity in the L/T Transition
Authors:
Liu, Michael C.; Leggett, S. K.; Golimowski, David A.; Chiu, Kuenley; Fan, Xiaohui; Geballe, T. R.; Schneider, Donald P.; Brinkmann, J.
Affiliation:
AA(Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822; .; Alfred P. Sloan Research Fellow.), AB(United Kingdom Infrared Telescope, Joint Astronomy Centre, 660 North A`ohoku Place, Hilo, HI 96720.), AC(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686.), AD(Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686.), AE(Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721.), AF(Gemini Observatory, 670 North A`ohoku Place, Hilo, HI 96720.), AG(Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802.), AH(Apache Point Observatory, 2001 Apache Point Road, P.O. Box 59, Sunspot, NM 88349.)
Publication:
The Astrophysical Journal, Volume 647, Issue 2, pp. 1393-1404. (ApJ Homepage)
Publication Date:
08/2006
Origin:
UCP
ApJ Keywords:
Stars: Binaries: Close, Stars: Binaries: General, Infrared: Stars, Stars: Atmospheres, Stars: Low-Mass, Brown Dwarfs, Techniques: High Anular Resolution
DOI:
10.1086/505561
Bibliographic Code:
2006ApJ...647.1393L

Abstract

We have resolved the newly discovered T dwarf SDSS J153417.05+161546.1 into a 0.11" binary using the Keck sodium laser guide star adaptive optics system. With an integrated-light near-IR spectral type of T3.5+/-0.5, this binary provides a new benchmark for studying the distinctive J-band brightening previously noted among early and mid-T dwarfs, using two brown dwarfs with different spectral types but having a common metallicity and age and very similar surface gravities. We estimate spectral types of T1.5+/-0.5 and T5.5+/-0.5 for the two components based on their near-IR colors, consistent with modeling the integrated-light spectrum as the blend of two components. The observed near-IR flux ratios of SDSS J1534+1615 are unique compared to all previously known substellar binaries: the component that is fainter at H and K' is brighter at J. This inversion of the near-IR fluxes is a manifestation of the J-band brightening within this individual binary system. Therefore, SDSS J1534+1615 demonstrates that the brightening can be intrinsic to ultracool photospheres (e.g., arising from cloud disruption and/or rapid increase in cloud sedimentation) and does not necessarily result from physical variations among the observed ensemble of T dwarfs (e.g., a range in masses, ages, and/or metallicities). We suggest that the apparently large amplitude of the J-band brightening may be due to a high incidence of unresolved binaries and that the true amplitude of the brightening phenomenon could be more modest. This scenario would imply that truly single objects in these spectral subclasses are relatively rare, in agreement with the small effective temperature range inferred for the L/T transition.

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.

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