Cool Stars 14 - Submitted Abstract # 250
This version created on 05 October 2006

The Role of Mass and Environment in (Sub)stellar Multiplicity


Adam Kraus, Caltech
Lynne Hillenbrand, Caltech
Russel White, University of Alabama

We will present a status report for two ongoing programs to identify
multiple (sub)stellar systems in nearby open clusters and young
associations.  Our first program is a high-resolution imaging survey
of low-mass stars and brown dwarfs using Keck Laser Guide Star
Adaptive Optics.  We have observed 65 members of Taurus-Auriga, Upper
Scorpius, and Praesepe, spanning a mass range of 0.15-0.02 Msun, and
identified 10  new candidate binary systems.  Our other program is a
seeing-limited search for wide (2-30") binary companions to all low-
and intermediate-mass (<2.5 Msun) members of the Taurus, Upper
Scorpius, and Chamaeleon-I associations using archival 2MASS
observations.  This search has identified 131 candidate binary
companions, including 39 new candidates.  We will interpret these
results in the context of other multiplicity surveys, which find that
high-mass binary systems are very common and span a wide range of
separations and mass ratios while lower-mass systems become
progressively less common, tighter, and more biased toward mass ratios
near unity.  Our results are generally consistent with these trends,
but we will also describe two newly-discovered low-mass systems which
seem to defy these expectations.

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