The shocking behaviour of WR140 near periastron

The prototype Wolf-Rayet WC7+04-5 colliding-wind binary system WR140 went through the periastron passage of its 8-year eccentric binary orbit in early 2001. High-resolution Chandra spectra showed resolved and blue-shifted lines before periastron and yielded abundances for eight different elements. The plasma was not in equilibrium, probably due to the collisionless nature of the shock transitions and the slow character of post-shock energy exchanges. Electron heat conduction into pre-shock gas was absent. After periastron, the spectrum was weaker due mainly to absorption by cool Wolf-Rayet star material.