On the morphogenesis of stellar flows - Application to planetary nebulae

Abstract

A large class of stellar systems (e.g., planetary nebulae (PNe), supernova envelopes, LBV stars, young stars in formation) shows structures in their accretion/ejection phase that have similar characteristics. In particular, one currently observes for these objects equatorial discs, axial ejections and stable bipolar shells. However these simple shapes, which are expected to be solutions of standard hydrodynamical equations, are not yet fully understood. In this paper, we suggest a new form of these equations that takes into account the fractality and the irreversibility of particle motion in such processes. Then we study in this framework a general infall or ejection motion in a central spherical potential. From the stationary solutions allowed by this new hydrodynamical system, we deduce a specific distribution of matter density, described in terms of probability density for ejection angles. A global classification of predicted shapes, depending on the values of conservative quantities such as (E^2,L^2,L_z), is given. These results are compared with the available observational data, and allows us to theoretically predict the possible existence of more complicated structures and of correlations between observable variables, which could be checked by future observations.