Cool Stars 14 - Submitted Abstract # 184
This version created on 05 October 2006

Activity and Kinematics of Ultracool Dwarfs


Sarah Schmidt, Barnard College/American Museum of Natural History/University of Washington
Kelle Cruz, American Museum of Natural History
James Liebert, University of Arizona
I. Neill Reid, Space Telescope Science Institute

We present an analysis of the activity and kinematics of a
volume-limited (20  pc) sample of over 150  M and L dwarfs
photometrically selected from the Two Micron All Sky Survey (2MASS).
New proper motion measurements and spectrophotometric distance
estimates are used to calculate tangential velocities.  We combine
these kinematic data with spectroscopic observations of H_alpha
emission to investigate the age/activity relation for low-mass stars
and brown dwarfs.  We also use our sample to examine variability in
ultracool dwarfs.  Eleven dwarfs out of 153 show evidence of
variability, ranging from small fluctuations to large flare events.
Assuming each dwarf is equally likely to flare, we estimate a flare
cycle of 5% for late-M dwarfs and 2% for L dwarfs.  We present data
for two of these flare observations - an amazing flare event on the
the M7 dwarf 2MASS~J1028404$-$143843 and strong, variable activity on
the L1 dwarf 2MASS~J10224821+5825453.

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