WR 140, a Colliding Wind Laboratory: The X-ray History

WR140 is a long-period, highly eccentric massive colliding wind binary system with well-determined orbital and stellar parameters. Periodically-varying X-ray emission is primarily generated in the hot shocked gas produced by the collision of the winds of the WC7pd + O5.5fc star components in the space between the two stars. We have obtained time-resolved broad-band X-ray spectrometry using the RXTE, Swift and NICER X-ray observatories through 3 orbital cycles, including two consecutive periastron passages. We discuss the X-ray variations in the context of the colliding wind model, and we consider the implications of the X-ray data for our understanding of the shocked plasma and its relation to the orbital parameters and other multi-wavelength observations .