Chandra Observation of SNR G54.1+0.3 -- a Close Cousin of the Crab   Nebula
  We present a {\it Chandra} ACIS observation of SNR G54.1+0.3. This supernova remnant is resolved into several distinct X-ray emitting components: a central bright point-like source (CXOU J193030.13+185214.1), a surrounding ring, bipolar elongations, plus low surface brightness diffuse emission. The spectra of these components are all well described by power-law models; the spectral index steepens with increasing distance from the point-like source. We find no evidence for any thermal plasma emission that would correspond to shocked interstellar medium or ejecta. The observed morphological and spectral characteristics suggest that G54.1+0.3 is the closest ``cousin'' of the Crab Nebula -- a pulsar wind nebula driven by a combination of equatorial and polar outflows from the putative pulsar represented by the point-like X-ray source. 
F.J. Lu (UMASS, Ihep-Cas), Q.D. Wang (UMASS), B. Aschenbach (MPE), Ph.   Durouchoux (CEA-Saclay), L.M. Song (IHEP-Cas)