  Supergiant fast X-ray transients (SFXTs) are a class of high-mass X-ray
binaries with possible counterparts in the high energy gamma rays. The Swift
SFXT Project has conducted a systematic investigation of the properties of
SFTXs on timescales ranging from minutes to years and in several intensity
states (from bright flares, to intermediate intensity states, and down to
almost quiescence). We also performed broad-band spectroscopy of outbursts, and
intensity-selected spectroscopy outside of outbursts. We demonstrated that
while the brightest phase of the outburst only lasts a few hours, further
activity is observed at lower fluxes for a remarkably longer time, up to weeks.
Furthermore, we assessed the fraction of the time these sources spend in each
phase, and their duty cycle of inactivity. We present the most recent results
from our investigation. The spectroscopic and, most importantly, timing
properties of SFXTs we have uncovered with Swift will serve as a guide in
search for the high energy emission from these enigmatic objects.
