The X-ray Lightcurve of WR 140

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.