Cool Stars 14 - Submitted Abstract # 370
This version created on 05 October 2006

Lithium Depletion in the Beta Pictoris Moving Group


Jennifer C.M. Yee, Swarthmore College
Eric L.N. Jensen, Swarthmore College

We present a study of lithium depletion in twelve late-type members of
the coeval Beta Pictoris Moving Group (BPMG) using equivalent width
measurements of the 6707.8 Angstrom Li I line from new
high-resolution, high-S/N spectra.  The age of this group (~12 Myr) is
well constrained because all of the stars in the sample have Hipparcos
distances.  We have compared the empirical data from this survey to
models of Li depletion by Baraffe et al.  (1998), D'Antona &
Mazzitelli (1997, 1998), and Siess, Dufour, & Forestini (2000).
Significantly more lithium depletion was observed in the sample than
is predicted for a group of this age.  In particular, the discrepancy
between the predicted and the observed lithium abundances is worse for
lower effective temperatures, suggesting a problem with theories
describing PMS lithium depletion.  Our data indicate that M stars
deplete lithium more rapidly than predicted, which could make M-type
post-T-Tauri stars difficult to identify.  In addition, we compare our
results to the work of Song, Bessell, & Zuckerman (2002) on HIP
112312.  In contrast to that work, we did not observe the lithium
depletion boundary of the BPMG;  none of the three M4.5 stars in the
sample showed evidence of lithium, indicating a lithium depletion
boundary later than M4.5, further underscoring the gap between age
estimates from lithium depletion and those from theoretical
evolutionary tracks.  

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