The probable association of SN 1957d in NGC 5236 (M83) with an unresolved radio source

Astrometric measurements of the position of SN 1957d in the spiral galaxy NGC 5236 using archival plates indicate that it is within 2 arcsec of the position of a point radio source of approximately Cas A strength on a VLA map made by Cowan and Branch (1982). This coincidence strongly suggests that the radio source originated from the supernova. If further investigation shows this point source to indeed be a supernova remnant, then this would be the first reported detection of an intermediate-age supernova remnant.