Contributed Talk - Splinter SNR
Tuesday, 12 September 2023, 14:00 (H 2035)
X-rays from shocked stellar winds in single and binary star systems
Dublin Institute for Advanced Studies
Winds from massive stars expand supersonically into their surroundings, and the resulting shocks produce hot X-ray-emitting plasma. For single stars these are parsec-scale bubbles such as bow shocks and ring nebulae, whereas in colliding-wind binary (CWB) systems the high wind density produces intense time- and space-dependent emission across the electromagnetic spectrum from radio to gamma-rays. I will present recent results on modelling the bow shocks of nearby massive stars such as Zeta Ophiuchi and the Bubble Nebula, compared with multiwavelength observations including radio and X-ray. Differently from single stars, the shocked wind in CWB systems is often dense enough and close enough to the stars such that the shocks are radiative. Comparing the relevant timescales, I will show that inverse-Compton cooling is often the dominant energy-loss mechanism for CWBs in eccentric or close binary orbits, although it is rarely included in models. 3D MHD simulations of the CWB system WR140 show that inverse-Compton cooling of the shocked plasma can trigger runaway cooling when the orbit is near periastron, producing strong compression and dynamical instabilities. The simulated X-ray lightcurve shows good correspondence with recent observations.