High Resolution Observations of Supernova Remnants at 80 MHz

Abstract

Observations of 10 supernova remnants with a resolution of about 4' arc at 80 MHz have enabled the spectra of several of these objects to be extended to this low frequency. From the results only the weIl-known supernova remnant G43·3-0·2 (W49B) shows conclusive evidence for curvature in its integrated spectrum at low frequencies in agreement with previous work. Some discrepancy between the conclusions and those from a related survey of smaIl diameter supernova remnants by Dulk and Slee (1972) is noted. Contour maps are presented for five of the more extended sources with a resolution equal to or greater than any previous maps. These results have been compared with higher frequency data in a search for possible changes in spectra across individual sources. G 189·1 + 2· 9 (IC 443) has been found to have a nearly constant spectral index over most of its extent with perhaps a somewhat flatter spectrum on its southern side.