Paper: astro-ph/0506352
Date: Wed, 15 Jun 2005 17:18:01 GMT (22kb)

Title: Constraints on Inner Disk Evolution Timescales: A Disk Census of the eta
Chamaeleontis Young Cluster

Authors: Karl E. Haisch Jr. (UVSC), Ray Jayawardhana (Toronto) and Joao Alves
(ESO)
Comments: accepted for publication in Astrophysical Journal Letters
\\
We present new L' (3.8-micron) observations of stars in the nearby (~97 pc)
young (~6 Myr) compact cluster around eta Chamaeleontis, obtained with the
European Southern Observatory's Very Large Telescope in Paranal, Chile. Our
data, combined with J,H, Ks photometry from the 2-Micron All Sky Survey, reveal
that only two of the 12 members surveyed harbor L'-band excesses consistent
with optically thick inner disks; both are also likely accretors. Intriguingly,
two other stars with possible evidence for on-going accretion, albeit at very
low rates, do not show significant infrared excess: this may imply substantial
grain growth and/or partial clearing of the inner disk region, as expected in
planet formation scenarios. Our findings suggest that eta Cha stars are in an
epoch when disks are rapidly evolving, perhaps due to processes related to
planet building, and provide further constraints on inner disk lifetimes.

\\ ( http://arXiv.org/abs/astro-ph/0506352 , 22kb)