Abstract

Acyclic High Energy Variability in Eta Carinae and WR 140

Michael Corcoran (USRA/CRESST & NASA-GSFC)

Kenji Hamaguchi (CRESST/UMBC/NASA-GSFC) Stan Owocki (U. Delaware) Chris Russell (U. Delaware) Julian Pittard (Leeds) E. Ross Parkin (ANU) Ted Gull (NASA-GSFC)

Eta Carinae and WR 140 are similar long-period colliding wind binaries in which X-ray emission is produced by a strong shock due to the collision of the powerful stellar winds. The change in the orientation and density of this shock as the stars revolve in their orbits changes the X-ray flux and spectrum in a phase dependent way. Monitoring observations with RXTE and other X-ray satellite observatories since the 1990s have detailed this variability but have also shown significant deviations from strict phase dependence in the form of short-term brightness changes (flares) and cycle-to-cycle differences. We examine these acylic variations in Eta Car and WR 140 and discuss what they tell us about the stability of the wind-wind collision shock.