2007ApJ...656.1038D

We follow up on our (Radhakrishnan & Deshpande) radically different interpretation of the observed structures and morphologies in the X-ray observations of the nebulae around young pulsars (PWNe). In our general model for PWNe (Radhakrishnan & Deshpande), originally motivated by the Chandra observations of the Vela X-ray nebula, the bright arcs, the jetlike feature, and the diffuse components in such nebulae can be explained together in detail, wherein the arcs are understood as traces of the particle beams from the two magnetic poles at the shock front. We consider this as important evidence for collimated particle beams from pulsars' magnetic poles. In this paper we discuss the variability in the features in the Vela X-ray nebula observed by Pavlov and coworkers and assess the relevance and implication of our model to the observations on the Crab and other remnants. Our basic picture after incorporating the signatures of free precession of the central compact object can readily account for the variability and significant asymmetries, including the bent jetlike features, in the observed morphologies. The implications of these findings are discussed.