X-Ray Spectral Observations of the Crab-like Supernova Remnants G21.5-0.9 and 3C 58
Becker, R. H.; Smith, A.; Davelaar, J.
Germany, Netherlands, United States
Abstract
Broad-band (2 - 10 keV) spectral data of the Crab-like supernova remnants 3C 58 and G21.5-0.9 have been obtained from the medium-energy instrument on EXOSAT. Both objects show a simple power-law spectrum with a spectral index of 0.72±0.12 for G21.5-0.9 and 1.30±0.26 for 3C 58. VLA 21 cm absorption measurements for G21.5-0.9 indicate a distance of 5.5 - 9.3 kpc.