  Young stars exhibit short-term photometric variability caused by mass
accretion events from circumstellar disks, the presence of dusty warps within
the inner disks, starspots that rotate across the stellar surfaces, and flares.
Long-term variability also occurs owing to starspot longevity and cycles, and
from changes in stellar angular momenta and activity as the stars age. We
propose to observe the Carina star-forming region in different bands with a
cadence of 30 minutes every night for one week per year to clarify the nature
of both the short-term and long-term variability of the thousands of young
stars in this region. By obtaining well-sampled multicolor lightcurves of this
dense young cluster, LSST would acquire the first statistically significant
data on how these objects vary on both short and long timescales. This
information will allow us to relate the observed variability to stellar
properties such as mass, age, binarity, and to environmental properties such as
location within or exterior to the H II region, and to the presence or absence
of a circumstellar disk.
