Search for radio emission from the young supernova remnants in NGC6946

Although recent supernovae in our own Galaxy are among the brightest radio sources in the sky - particularly Cas A and the Crab Nebula (500-1,000 yr post-outburst) - the evolution of their radio emission from outburst to the present is, of course, unknown. Unless and until we have the opportunity to study a new galactic supernova, our information on the immediate post-outburst radio properties of supernova remnants must come from studies of identified supernovae in external galaxies. NGC6946 is one galaxy in which such a study is particularly favourable both because supernovae occur frequently in this galaxy - four supernovae have been identified since 1917 - and because of its relative proximity. Two previous searches have failed to detect radio emission from these remnants^1,2. However, the greater sensitivity presently available at radio wavelengths allows us not only to conduct a more sensitive search for these remnants but also to determine whether the radio emission has brightened since the last surveys ∼ 5 yr ago.