Colloquium on Apr. 27, 2023

Wind-Blown Nebulae from Single and Binary Massive Stars

Speaker: Jonathan Mackey (DIAS)

Venue: Video Conference

Time: 15:00 PM, Thursday, Apr. 27, 2023

Abstract:

Winds from massive stars expand supersonically into their surroundings, creating dynamic and fascinating nebulae that can give us insight into physical processes in interstellar plasma, and into the evolutionary history of the stars.  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.  Shock physics, particle acceleration and radiative processes can be investigated.  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.  I will discuss prospects for using 3D simulations, together with multi-epoch observations, to constrain the stellar wind properties of the massive stars.