event
Wednesday 11 Jul 2012: Physics of wind-accretion in microquasars and recurrent novae
Dr Rolf Walden - ENS Lyon
Physics, 4th floor 14:00-14:45
About half of the microquasar do not undergo Roche lobe overflow but are accreting from the powerful wind of a massive companion. Similarly, about half of the known 11 recurrent novae - presumably progenitors of SNIa - are wind-accretors.
Despite of its obvious importance, the physics of wind-accretion is not well explored so far. I will report on numerical simulations in progress, showing that wind-accretion is highly efficient in systems where the companion star is heavily mass loosing with strong winds. This work demonstrates that in such systems no classical Newtonian disk is formed. Depending on the wind speeds, two different modes are identified. Slow winds result in the formation of a geometrically thick disk. Angular momentum is advected by two strong shocks. Fast wind systems, on the other hand, hardly develop any disk at all.
I will discuss the consequences for recurrent nova systems, arguing that such systems likely develop into an SNIa, either of the singly or the double degenerate type. For the microquasars, the irradation of the X-rays originating from the vicinity of the compact object into the athmosphere of the high mass companion can severely affect its wind speed. This back-coupling may stand at the origin of different states observed in these objects.
