Chandra Observation of SNR G 54 . 1 + 0 . 3 — a Close Cousin of the Crab Nebula

We present a 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, bipo-lar elongations, plus low surface brightness diffuse emission. The spectra of these components are all well described by power-law models; the spectral index steep-ens with increasing distance from the point-like source. We find no evidence for any thermal plasma emission that would correspond to shocked interstel-lar 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.