Further Evidence for Collimated Particle Beams from Pulsars and Precession

We follow up on our (Radhakrishnan & Deshpande, 2001: RD01) radicallydifferent interpretation of the observed structures and morphologies in thex-ray observations of the nebulae around young pulsars (PWNe). In our generalmodel for PWNe (RD01), originally motivated by the Chandra observations of theVela X-ray nebula, the bright arcs, the jet-like feature and the diffusecomponents in such nebulae can be explained together in detail, wherein thearcs are understood as traces of the particle beams from the two magnetic polesat the shock front. We consider this as important evidence for collimatedparticle beams from pulsars' magnetic poles. In this paper, we discuss thevariability in the features in the Vela X-ray nebula observed by Pavlov et al.(2003), and assess the relevance and implication of our model to theobservations on the Crab and other remnants. Our basic picture afterincorporating the signatures of free precession of the central compact objectcan readily account for the variability and significant asymmetries, includingthe bent jet-like features, in the observed morphologies. The implications ofthese findings are discussed.Comment: Minor revision; 12 (9+3) pages, 3 figures; To appear in Ap