Multiplicity among young brown dwarfs and very low mass stars

Ahmic, Mirza and Jayawardhana, Ray and Brandeker, Alexis and Scholz, Alexander and van Kerkwijk, Marten H. and Delgado-Donate, Eduardo and Froebrich, Dirk (2007) Multiplicity among young brown dwarfs and very low mass stars. Astrophysical Journal, 671 (2). pp. 2074-2081. ISSN 0004-637X . (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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We report on a near-infrared adaptive optics imaging survey of 31 young brown dwarfs and very low mass (VLM) stars, 28 of which are in the Chamaeleon I star-forming region, using the ESO Very Large Telescope. We resolve the suspected 0: 1600 (similar to 26 AU) binary Cha H alpha 2 and present two new binaries, Hn 13 and CHXR 15, with separations of 0: 1300 (similar to 20 AU) and 0.30" (similar to 50 AU), respectively; the latter is one of the widest VLM systems known. We find a binary frequency of 11(-6)(+9)%, thus confirming the trend for a lower binary frequency with decreasing mass. By combining our work with previous surveys, we arrive at the largest sample of young VLM objects ( 72) with high angular resolution imaging to date. Its multiplicity fraction is in statistical agreement with that for VLM objects in the field. Furthermore, we note that many field stellar binaries with lower binding energies and/or wider cross sections have survived dynamical evolution and that statistical models suggest tidal disruption by passing stars is unlikely to affect the binary properties of our systems. Thus, we argue that there is no significant evolution of multiplicity with age among brown dwarfs and VLM stars in OB and Tassociations between a few megayears to several gigayears. Instead, the observations so far suggest that VLM objects are either less likely to be born in fragile multiple systems than solar-mass stars or such systems are disrupted very early.

Item Type: Article
Uncontrolled keywords: binaries : general; planetary systems; stars : formation; stars : low-mass; brown dwarfs; stars : luminosity function; mass function
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Suzanne Duffy
Date Deposited: 21 Apr 2008 08:30
Last Modified: 13 Jun 2014 08:39
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