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Title:
Hubble Space Telescope Observations of Binary Very Low Mass Stars and Brown Dwarfs
Authors:
Gizis, John E.; Reid, I. Neill; Knapp, Gillian R.; Liebert, James; Kirkpatrick, J. Davy; Koerner, David W.; Burgasser, Adam J.
Affiliation:
AA(Department of Physics and Astronomy, University of Delaware, Newark, DE 19716; ), AB(Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218), AC(Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001), AD(Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721), AE(Infrared Processing and Analysis Center, 100-22, California Institute of Technology, Pasadena, CA 91125), AF(Department of Physics and Astronomy, Northern Arizona University, Box 6010, Flagstaff, AZ 86011-6010), AG(Division of Astronomy and Astrophysics, 8965 Math Science Building, UCLA, Los Angeles, CA 90095-1562)
Publication:
The Astronomical Journal, Volume 125, Issue 6, pp. 3302-3310. (AJ Homepage)
Publication Date:
06/2003
Origin:
UCP
AJ Keywords:
Stars: Binaries: General, Stars: Low-Mass, Brown Dwarfs
DOI:
10.1086/374991
Bibliographic Code:
2003AJ....125.3302G

Abstract

We present analysis of Hubble Space Telescope (HST) images of 82 nearby field late M and L dwarfs. We resolve 13 of these systems into double M/L dwarf systems and identify an additional possible binary. Combined with previous observations of 20 L dwarfs, we derive an observed binary fraction for ultracool dwarfs of 17+4-3%, where the statistics included systems with separations in the range 1.6-16 AU. We argue that accounting for biases and incompleteness leads to an estimated binary fraction 15%+/-5% in the range 1.6-16 AU. No systems wider than 16 AU are seen, implying that the wide companion frequency is less than 1.7%; the distribution of orbital separation is peaked at ~2-4 AU and differs greatly from the G dwarf binary distribution. Indirect evidence suggests that the binary fraction is ~5%+/-3% for separations less than 1.6 AU. We find no evidence for differences in the binary fraction between stellar late M and L dwarfs and substellar L dwarfs. We note, however, that the widest (greater than 10 AU) systems in our sample are all of earlier (M8-L0) spectral type; a larger sample is needed to determine if this is a real effect. One system with a spectral type of L7 has a secondary that is fainter in the HST F814W filter but brighter in F1042M; we argue that this secondary is an early T dwarf.
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