L-dwarf binaries in the 20-parsec sample
Abstract
We have used the NICMOS NIC1 camera on the Hubble Space Telescope to obtain high-resolution near-infrared images of 27 nearby ultracool dwarfs with formal distance estimates less than 20 parsecs. One target, 2MASS J22551861-5713056, is resolved as a binary system, with a 4:1 flux ratio in the F110W passband. The primary has spectral type L6, and the revised spectroscopic parallax places it at a distance of ~12 parsecs. The secondary is likely to have a spectral type between L8 and T1. The remaining 26 dwarfs are unresolved. Combining the present results with our earlier NICMOS (Near-Infrared Camera and Multi Object Spectrometer) observations and literature data, high-resolution imaging exists for 72 of the 85 L dwarfs in the current 20-parsec census. We derive a formal frequency of 15.3+5.1 −3.3% for resolved binaries in the local L-dwarf population. The frequency drops to 12.5+5.3 −3.0% if we take Malmquist bias into account. The NICMOS observations are capable of detecting systems with mass ratios q>0.2, but all known binaries are near equal-mass, suggesting that low-q systems either fail to form, or have short lifetimes.
Additional Information
© 2008 The American Astronomical Society. Received 2007 October 4, accepted for publication 2007 November 15. Published 2008 January 15. Print publication: Issue 2 (2008 February). Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The observations described in this paper are associated with HST program #10879, and those data were obtained via the HST data archive facilities maintained at the Space Telescope Science Institute. Support for this research was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. K.L.C. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-0401418. M.C.L. acknowledges support from NSF grant AST-0507833 and an Alfred P. Sloan Research Fellowship. Support for K.L.C. was provided by NASA through the Spitzer Space Telescope Fellowship Program, through a contract issued by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This publication makes use of data from the 2 Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, and funded by the National Aeronautics and Space Administration and the National Science Foundation. 2MASS data were obtained from the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.Attached Files
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Additional details
- Eprint ID
- 12021
- Resolver ID
- CaltechAUTHORS:REIaj08a
- NASA
- NAS 5-26555
- Space Telescope Science Institute
- NSF Astronomy and Astrophysics Fellowship
- AST-0401418
- NSF
- AST-0507833
- Alfred P. Sloan Foundation
- NASA Spitzer Fellowship
- NASA/JPL/Caltech
- Created
-
2008-10-20Created from EPrint's datestamp field
- Updated
-
2021-11-08Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)