Observations of the supernova remnant G54.1+0.3: X-ray spectrum and evidence for an X-ray jet

We present analyses of the ROSAT PSPC and the ASCA SIS and GIS observations of the Crab-like supernova remnant (SNR) G54.1+0.3. The spectrum is best fitted by a power law model with a photon index of -1.9+0.2-0.2, absorbed energy flux of 6.8 10-12 erg cm-2 s-1 in the 0.7-10 keV band, and a column density of 17.9+2.8-2.5 10²¹ cm-2. The high absorption column density indicates a distance close to the radius of the galaxy. The 0.7-10.0 keV X-ray luminosity of G54.1+0.3 is 1.4 1035 d₁₀² erg s-1, where d10 is the distance in 10 kpc. With an image restoration method, we have deconvolved the X-ray image of the remnant. There is evidence for an X-ray jet pointing to the north-east with a length of about 40″ measured from the center of the nebula. Its X-ray luminosity in the 0.1-2.4 keV range is about 2.1 1034 d₁₀² erg s-1. The X-ray jet is consistent with the radio extension of G54.1+0.3 to the north-east in both direction and position.