Three fields containing young pulsars - The observable lifetime of supernova remnants

Data for fields containing three of the youngest known pulsars reveal little radiation which can be attributable to supernova remnants associated with their formation. The present observations suggest a mean observable lifetime of less than about 20,000 yr for both pulsar and blast-wave powered remnants. The relatively rapid luminosity decline of both of these phenomena can be explained by a scenario in which the most massive supernova occurs within regions of low density bounded at radii of 10-30 pc by high-density shells.