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Session 38 - Disks and Bipolar Outflows from Hot Stars.
Display session, Tuesday, June 11
We propose a model for the production of Jets and Anase in Planetary Nebulae (PN) which utilizes the succesful Interacting Stellar Winds Scenario. In our model we consider a Proto-Planetary Nebulae (PPN) wind blown bubble driven by an evolving fast wind. The fast wind expands into a previously ejected aspherical slow wind circumstellar envelope. During the early PPN stage when the velocity of the fast wind is less than 160 km/s the bubble will be in the momentum conserving phase. The presence of a equator to pole density contrast in the slow wind makes bubble ellipitcal (prolate). The fast wind will encounter the shocks bounding the bubble obliquely and the post-shock fast wind flow will be focused towards the equator forming a converging conical stream. It has been shown by Canto et al. (1988) that well collimated jets can be produced by such converging streams at the tip of the conical flow. We apply the Canto et al. model to a PPN bubble and show how the time history of the jets depends on the evolution of the fast wind as well as on the equator to pole density contrast in the slow wind.
Our model provides a means for projecting the ansae beyound the swept-up slow wind shell which defines the boundry of the concentric stellar windıs interaction zone. The results of our calculations show that jets produced by converging streams in PPN bubbles have characteristic velocity and size scales which are well matched to observations of PN ansae. Since the momentum conserving phase has a finite lifetime and our poposed mechanism should not work in the energy conserving phase our sceario provides a definite time and velocity scales for the prodution of jets and hence anase in PNe. Finally we find large densities in the model jets which implies short recombination timescales and can therefore explain the observed low ioniztion states in these objects.
Program listing for Tuesday