  WR 140 is a canonical massive "colliding wind" binary system in which
periodically-varying X-ray emission is produced by the collision between the
wind of the WC7 and O4-5 star components in the space between the two stars. We
have obtained X-ray observations using the RXTE satellite observatory through
almost one complete orbital cycle including two consecutive periastron
passages. We discuss the results of this observing campaign, and the
implications of the X-ray data for our understanding of the orbital dynamics
and the stellar mass loss.
